Adding upstream version 4.22.0.upstream/4.22.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 9029 insertions, 0 deletions

diff --git a/upstream/archlinux/man1p/ex.1p b/upstream/archlinux/man1p/ex.1p
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+'\" et
+.TH EX "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
+.\"
+.SH PROLOG
+This manual page is part of the POSIX Programmer's Manual.
+The Linux implementation of this interface may differ (consult
+the corresponding Linux manual page for details of Linux behavior),
+or the interface may not be implemented on Linux.
+.\"
+.SH NAME
+ex
+\(em text editor
+.SH SYNOPSIS
+.LP
+.nf
+ex \fB[\fR-rR\fB] [\fR-s|-v\fB] [\fR-c \fIcommand\fB] [\fR-t \fItagstring\fB] [\fR-w \fIsize\fB] [\fIfile\fR...\fB]\fR
+.fi
+.SH DESCRIPTION
+The
+.IR ex
+utility is a line-oriented text editor. There are two other modes of
+the editor\(emopen and visual\(emin which screen-oriented editing is
+available. This is described more fully by the
+.IR ex
+.BR open
+and
+.BR visual
+commands and in
+.IR "\fIvi\fR\^".
+.P
+If an operand is
+.BR '\-' ,
+the results are unspecified.
+.P
+This section uses the term
+.IR "edit buffer"
+to describe the current working text. No specific implementation is
+implied by this term. All editing changes are performed on the edit
+buffer, and no changes to it shall affect any file until an editor
+command writes the file.
+.P
+Certain terminals do not have all the capabilities necessary to support
+the complete
+.IR ex
+definition, such as the full-screen editing commands (\c
+.IR "visual mode"
+or
+.IR "open mode" ).
+When these commands cannot be supported on such terminals, this
+condition shall not produce an error message such as ``not an editor
+command'' or report a syntax error. The implementation may either
+accept the commands and produce results on the screen that are the
+result of an unsuccessful attempt to meet the requirements of this volume of POSIX.1\(hy2017 or
+report an error describing the terminal-related deficiency.
+.SH OPTIONS
+The
+.IR ex
+utility shall conform to the Base Definitions volume of POSIX.1\(hy2017,
+.IR "Section 12.2" ", " "Utility Syntax Guidelines",
+except for the unspecified usage of
+.BR '\-' ,
+and that
+.BR '\(pl' 
+may be recognized as an option delimiter as well as
+.BR '\-' .
+.P
+The following options shall be supported:
+.IP "\fB\-c\ \fIcommand\fR" 10
+Specify an initial command to be executed in the first edit buffer
+loaded from an existing file (see the EXTENDED DESCRIPTION section).
+Implementations may support more than a single
+.BR \-c
+option. In such implementations, the specified commands shall be
+executed in the order specified on the command line.
+.IP "\fB\-r\fP" 10
+Recover the named files (see the EXTENDED DESCRIPTION section).
+Recovery information for a file shall be saved during an editor or
+system crash (for example, when the editor is terminated by a signal
+which the editor can catch), or after the use of an
+.IR ex
+.BR preserve
+command.
+.RS 10 
+.P
+A
+.IR crash
+in this context is an unexpected failure of the system or utility that
+requires restarting the failed system or utility. A system crash
+implies that any utilities running at the time also crash. In the case
+of an editor or system crash, the number of changes to the edit buffer
+(since the most recent
+.BR preserve
+command) that will be recovered is unspecified.
+.P
+If no
+.IR file
+operands are given and the
+.BR \-t
+option is not specified, all other options, the
+.IR EXINIT
+variable, and any
+.BR .exrc
+files shall be ignored; a list of all recoverable files available to
+the invoking user shall be written, and the editor shall exit normally
+without further action.
+.RE
+.IP "\fB\-R\fP" 10
+Set
+.BR readonly
+edit option.
+.IP "\fB\-s\fP" 10
+Prepare
+.IR ex
+for batch use by taking the following actions:
+.RS 10 
+.IP " *" 4
+Suppress writing prompts and informational (but not diagnostic)
+messages.
+.IP " *" 4
+Ignore the value of
+.IR TERM
+and any implementation default terminal type and assume the terminal is
+a type incapable of supporting open or visual modes; see the
+.BR visual
+command and the description of
+.IR "\fIvi\fR\^".
+.IP " *" 4
+Suppress the use of the
+.IR EXINIT
+environment variable and the reading of any
+.BR .exrc
+file; see the EXTENDED DESCRIPTION section.
+.IP " *" 4
+Suppress autoindentation, ignoring the value of the
+.BR autoindent
+edit option.
+.RE
+.IP "\fB\-t\ \fItagstring\fR" 10
+Edit the file containing the specified
+.IR tagstring ;
+see
+.IR "\fIctags\fR\^".
+The tags feature represented by
+.BR \-t
+.IR tagstring
+and the
+.BR tag
+command is optional. It shall be provided on any system that also
+provides a conforming implementation of
+.IR ctags ;
+otherwise, the use of
+.BR \-t
+produces undefined results. On any system, it shall be an error to
+specify more than a single
+.BR \-t
+option.
+.IP "\fB\-v\fP" 10
+Begin in visual mode (see
+.IR "\fIvi\fR\^").
+.IP "\fB\-w\ \fIsize\fR" 10
+Set the value of the
+.IR window
+editor option to
+.IR size .
+.SH OPERANDS
+The following operand shall be supported:
+.IP "\fIfile\fR" 10
+A pathname of a file to be edited.
+.SH STDIN
+The standard input consists of a series of commands and input text, as
+described in the EXTENDED DESCRIPTION section. The implementation may
+limit each line of standard input to a length of
+{LINE_MAX}.
+.P
+If the standard input is not a terminal device, it shall be as if the
+.BR \-s
+option had been specified.
+.P
+If a read from the standard input returns an error, or if the editor
+detects an end-of-file condition from the standard input, it shall be
+equivalent to a SIGHUP asynchronous event.
+.SH "INPUT FILES"
+Input files shall be text files or files that would be text files
+except for an incomplete last line that is not longer than
+{LINE_MAX}\-1
+bytes in length and contains no NUL characters. By default, any
+incomplete last line shall be treated as if it had a trailing
+<newline>.
+The editing of other forms of files may optionally be allowed by
+.IR ex
+implementations.
+.P
+The
+.BR .exrc
+files and source files shall be text files consisting of
+.IR ex
+commands; see the EXTENDED DESCRIPTION section.
+.P
+By default, the editor shall read lines from the files to be edited
+without interpreting any of those lines as any form of editor command.
+.SH "ENVIRONMENT VARIABLES"
+The following environment variables shall affect the execution of
+.IR ex :
+.IP "\fICOLUMNS\fP" 10
+Override the system-selected horizontal screen size. See the Base Definitions volume of POSIX.1\(hy2017,
+.IR "Chapter 8" ", " "Environment Variables"
+for valid values and results when it is unset or null.
+.IP "\fIEXINIT\fP" 10
+Determine a list of
+.IR ex
+commands that are executed on editor start-up. See the EXTENDED
+DESCRIPTION section for more details of the initialization phase.
+.IP "\fIHOME\fP" 10
+Determine a pathname of a directory that shall be searched for an
+editor start-up file named
+.BR .exrc ;
+see the EXTENDED DESCRIPTION section.
+.IP "\fILANG\fP" 10
+Provide a default value for the internationalization variables that are
+unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
+.IR "Section 8.2" ", " "Internationalization Variables"
+for the precedence of internationalization variables used to determine
+the values of locale categories.)
+.IP "\fILC_ALL\fP" 10
+If set to a non-empty string value, override the values of all the
+other internationalization variables.
+.IP "\fILC_COLLATE\fP" 10
+.br
+Determine the locale for the behavior of ranges, equivalence classes,
+and multi-character collating elements within regular expressions.
+.IP "\fILC_CTYPE\fP" 10
+Determine the locale for the interpretation of sequences of bytes of
+text data as characters (for example, single-byte as opposed to
+multi-byte characters in arguments and input files), the behavior of
+character classes within regular expressions, the classification of
+characters as uppercase or lowercase letters, the case conversion of
+letters, and the detection of word boundaries.
+.IP "\fILC_MESSAGES\fP" 10
+.br
+Determine the locale that should be used to affect the format and
+contents of diagnostic messages written to standard error.
+.IP "\fILINES\fP" 10
+Override the system-selected vertical screen size, used as the number
+of lines in a screenful and the vertical screen size in visual mode.
+See the Base Definitions volume of POSIX.1\(hy2017,
+.IR "Chapter 8" ", " "Environment Variables"
+for valid values and results when it is unset or null.
+.IP "\fINLSPATH\fP" 10
+Determine the location of message catalogs for the processing of
+.IR LC_MESSAGES .
+.IP "\fIPATH\fP" 10
+Determine the search path for the shell command specified in the
+.IR ex
+editor commands
+.BR ! ,
+.BR shell ,
+.BR read ,
+and
+.BR write ,
+and the open and visual mode command
+.BR ! ;
+see the description of command search and execution in
+.IR "Section 2.9.1.1" ", " "Command Search and Execution".
+.IP "\fISHELL\fP" 10
+Determine the preferred command line interpreter for use as the default
+value of the
+.BR shell
+edit option.
+.IP "\fITERM\fP" 10
+Determine the name of the terminal type. If this variable is unset or
+null, an unspecified default terminal type shall be used.
+.SH "ASYNCHRONOUS EVENTS"
+The following term is used in this and following sections to specify
+command and asynchronous event actions:
+.IP "\fIcomplete\ write\fP" 10
+.br
+A complete write is a write of the entire contents of the edit buffer
+to a file of a type other than a terminal device, or the saving of the
+edit buffer caused by the user executing the
+.IR ex
+.BR preserve
+command. Writing the contents of the edit buffer to a temporary file
+that will be removed when the editor exits shall not be considered a
+complete write.
+.P
+The following actions shall be taken upon receipt of signals:
+.IP SIGINT 10
+If the standard input is not a terminal device,
+.IR ex
+shall not write the file or return to command or text input mode, and
+shall exit with a non-zero exit status.
+.RS 10 
+.P
+Otherwise, if executing an open or visual text input mode command,
+.IR ex
+in receipt of SIGINT shall behave identically to its receipt of the
+<ESC>
+character.
+.P
+Otherwise:
+.IP " 1." 4
+If executing an
+.IR ex
+text input mode command, all input lines that have been completely
+entered shall be resolved into the edit buffer, and any partially
+entered line shall be discarded.
+.IP " 2." 4
+If there is a currently executing command, it shall be aborted and a
+message displayed. Unless otherwise specified by the
+.IR ex
+or
+.IR vi
+command descriptions, it is unspecified whether any lines modified by
+the executing command appear modified, or as they were before being
+modified by the executing command, in the buffer.
+.RS 4 
+.P
+If the currently executing command was a motion command, its associated
+command shall be discarded.
+.RE
+.IP " 3." 4
+If in open or visual command mode, the terminal shall be alerted.
+.IP " 4." 4
+The editor shall then return to command mode.
+.RE
+.IP SIGCONT 10
+The screen shall be refreshed if in open or visual mode.
+.IP SIGHUP 10
+If the edit buffer has been modified since the last complete write,
+.IR ex
+shall attempt to save the edit buffer so that it can be recovered later
+using the
+.BR \-r
+option or the
+.IR ex
+.BR recover
+command. The editor shall not write the file or return to command or
+text input mode, and shall terminate with a non-zero exit status.
+.IP SIGTERM 10
+Refer to SIGHUP.
+.P
+The action taken for all other signals is unspecified.
+.SH STDOUT
+The standard output shall be used only for writing prompts to the user,
+for informational messages, and for writing lines from the file.
+.SH STDERR
+The standard error shall be used only for diagnostic messages.
+.SH "OUTPUT FILES"
+The output from
+.IR ex
+shall be text files.
+.SH "EXTENDED DESCRIPTION"
+Only the
+.IR ex
+mode of the editor is described in this section. See
+.IR "\fIvi\fR\^"
+for additional editing capabilities available in
+.IR ex .
+.P
+When an error occurs,
+.IR ex
+shall write a message. If the terminal supports a standout mode (such
+as inverse video), the message shall be written in standout mode. If
+the terminal does not support a standout mode, and the edit option
+.BR errorbells
+is set, an alert action shall precede the error message.
+.P
+By default,
+.IR ex
+shall start in command mode, which shall be indicated by a
+.BR :
+prompt; see the
+.BR prompt
+command. Text input mode can be entered by the
+.BR append ,
+.BR insert ,
+or
+.BR change
+commands; it can be exited (and command mode re-entered) by typing a
+<period>
+(\c
+.BR '.' )
+alone at the beginning of a line.
+.SS "Initialization in ex and vi"
+.P
+The following symbols are used in this and following sections to
+specify locations in the edit buffer:
+.IP "\fIalternate\ and\ current\ pathnames\fP" 6
+.br
+Two pathnames, named
+.IR current
+and
+.IR alternate ,
+are maintained by the editor. Any
+.IR ex
+commands that take filenames as arguments shall set them as follows:
+.RS 6 
+.IP " 1." 4
+If a
+.IR file
+argument is specified to the
+.IR ex
+.BR edit ,
+.BR ex ,
+or
+.BR recover
+commands, or if an
+.IR ex
+.BR tag
+command replaces the contents of the edit buffer.
+.RS 4 
+.IP " a." 4
+If the command replaces the contents of the edit buffer, the current
+pathname shall be set to the
+.IR file
+argument or the file indicated by the tag, and the alternate pathname
+shall be set to the previous value of the current pathname.
+.IP " b." 4
+Otherwise, the alternate pathname shall be set to the
+.IR file
+argument.
+.RE
+.IP " 2." 4
+If a
+.IR file
+argument is specified to the
+.IR ex
+.BR next
+command:
+.RS 4 
+.IP " a." 4
+If the command replaces the contents of the edit buffer, the current
+pathname shall be set to the first
+.IR file
+argument, and the alternate pathname shall be set to the previous
+value of the current pathname.
+.RE
+.IP " 3." 4
+If a
+.IR file
+argument is specified to the
+.IR ex
+.BR file
+command, the current pathname shall be set to the
+.IR file
+argument, and the alternate pathname shall be set to the previous
+value of the current pathname.
+.IP " 4." 4
+If a
+.IR file
+argument is specified to the
+.IR ex
+.BR read
+and
+.BR write
+commands (that is, when reading or writing a file, and not to the
+program named by the
+.BR shell
+edit option), or a
+.IR file
+argument is specified to the
+.IR ex
+.BR xit
+command:
+.RS 4 
+.IP " a." 4
+If the current pathname has no value, the current pathname shall be
+set to the
+.IR file
+argument.
+.IP " b." 4
+Otherwise, the alternate pathname shall be set to the
+.IR file
+argument.
+.RE
+.P
+If the alternate pathname is set to the previous value of the current
+pathname when the current pathname had no previous value, then the
+alternate pathname shall have no value as a result.
+.RE
+.IP "\fIcurrent\ line\fP" 6
+.br
+The line of the edit buffer referenced by the cursor. Each command
+description specifies the current line after the command has been
+executed, as the
+.IR "current line value" .
+When the edit buffer contains no lines, the current line shall be zero;
+see
+.IR "Addressing in ex".
+.IP "\fIcurrent\ column\fP" 6
+.br
+The current display line column occupied by the cursor. (The columns
+shall be numbered beginning at 1.) Each command description specifies
+the current column after the command has been executed, as the
+.IR "current column"
+value. This column is an
+.IR ideal
+column that is remembered over the lifetime of the editor. The actual
+display line column upon which the cursor rests may be different from
+the current column; see the cursor positioning discussion in
+.IR "Command Descriptions in vi".
+.IP "\fIset\ to\ non-<blank>\fP" 6
+.br
+A description for a current column value, meaning that the current
+column shall be set to the last display line column on which is
+displayed any part of the first non-\c
+<blank>
+of the line. If the line has no non-\c
+<blank>
+non-\c
+<newline>
+characters, the current column shall be set to the last display line
+column on which is displayed any part of the last non-\c
+<newline>
+character in the line. If the line is empty, the current column shall
+be set to column position 1.
+.P
+The length of lines in the edit buffer may be limited to
+{LINE_MAX}
+bytes. In open and visual mode, the length of lines in the edit buffer
+may be limited to the number of characters that will fit in the
+display. If either limit is exceeded during editing, an error message
+shall be written. If either limit is exceeded by a line read in from a
+file, an error message shall be written and the edit session may be
+terminated.
+.P
+If the editor stops running due to any reason other than a user
+command, and the edit buffer has been modified since the last complete
+write, it shall be equivalent to a SIGHUP asynchronous event. If the
+system crashes, it shall be equivalent to a SIGHUP asynchronous event.
+.P
+During initialization (before the first file is copied into the edit
+buffer or any user commands from the terminal are processed) the
+following shall occur:
+.IP " 1." 4
+If the environment variable
+.IR EXINIT
+is set, the editor shall execute the
+.IR ex
+commands contained in that variable.
+.IP " 2." 4
+If the
+.IR EXINIT
+variable is not set, and all of the following are true:
+.RS 4 
+.IP " a." 4
+The
+.IR HOME
+environment variable is not null and not empty.
+.IP " b." 4
+The file
+.BR .exrc
+in the directory referred to by the
+.IR HOME
+environment variable:
+.RS 4 
+.IP " i." 5
+Exists
+.IP ii. 5
+Is owned by the same user ID as the real user ID of the process or the
+process has appropriate privileges
+.IP iii. 5
+Is not writable by anyone other than the owner
+.RE
+.P
+the editor shall execute the
+.IR ex
+commands contained in that file.
+.RE
+.IP " 3." 4
+If and only if all of the following are true:
+.RS 4 
+.IP " a." 4
+The current directory is not referred to by the
+.IR HOME
+environment variable.
+.IP " b." 4
+A command in the
+.IR EXINIT
+environment variable or a command in the
+.BR .exrc
+file in the directory referred to by the
+.IR HOME
+environment variable sets the editor option
+.BR exrc .
+.IP " c." 4
+The
+.BR .exrc
+file in the current directory:
+.RS 4 
+.IP " i." 5
+Exists
+.IP ii. 5
+Is owned by the same user ID as the real user ID of the process, or by
+one of a set of implementation-defined user IDs
+.IP iii. 5
+Is not writable by anyone other than the owner
+.RE
+.P
+the editor shall attempt to execute the
+.IR ex
+commands contained in that file.
+.RE
+.P
+Lines in any
+.BR .exrc
+file that are blank lines shall be ignored. If any
+.BR .exrc
+file exists, but is not read for ownership or permission reasons, it
+shall be an error.
+.P
+After the
+.IR EXINIT
+variable and any
+.BR .exrc
+files are processed, the first file specified by the user shall be
+edited, as follows:
+.IP " 1." 4
+If the user specified the
+.BR \-t
+option, the effect shall be as if the
+.IR ex
+.BR tag
+command was entered with the specified argument, with the exception
+that if tag processing does not result in a file to edit, the effect
+shall be as described in step 3. below.
+.IP " 2." 4
+Otherwise, if the user specified any command line
+.IR file
+arguments, the effect shall be as if the
+.IR ex
+.BR edit
+command was entered with the first of those arguments as its
+.IR file
+argument.
+.IP " 3." 4
+Otherwise, the effect shall be as if the
+.IR ex
+.BR edit
+command was entered with a nonexistent filename as its
+.IR file
+argument. It is unspecified whether this action shall set the current
+pathname. In an implementation where this action does not set the
+current pathname, any editor command using the current pathname shall
+fail until an editor command sets the current pathname.
+.P
+If the
+.BR \-r
+option was specified, the first time a file in the initial argument
+list or a file specified by the
+.BR \-t
+option is edited, if recovery information has previously been saved
+about it, that information shall be recovered and the editor shall
+behave as if the contents of the edit buffer have already been
+modified. If there are multiple instances of the file to be recovered,
+the one most recently saved shall be recovered, and an informational
+message that there are previous versions of the file that can be
+recovered shall be written. If no recovery information about a file is
+available, an informational message to this effect shall be written,
+and the edit shall proceed as usual.
+.P
+If the
+.BR \-c
+option was specified, the first time a file that already exists
+(including a file that might not exist but for which recovery
+information is available, when the
+.BR \-r
+option is specified) replaces or initializes the contents of the edit
+buffer, the current line shall be set to the last line of the edit
+buffer, the current column shall be set to non-\c
+<blank>,
+and the
+.IR ex
+commands specified with the
+.BR \-c
+option shall be executed. In this case, the current line and current
+column shall not be set as described for the command associated with
+the replacement or initialization of the edit buffer contents. However,
+if the
+.BR \-t
+option or a
+.BR tag
+command is associated with this action, the
+.BR \-c
+option commands shall be executed and then the movement to the tag
+shall be performed.
+.P
+The current argument list shall initially be set to the filenames
+specified by the user on the command line. If no filenames are
+specified by the user, the current argument list shall be empty. If the
+.BR \-t
+option was specified, it is unspecified whether any filename resulting
+from tag processing shall be prepended to the current argument list. In
+the case where the filename is added as a prefix to the current
+argument list, the current argument list reference shall be set to that
+filename. In the case where the filename is not added as a prefix to
+the current argument list, the current argument list reference shall
+logically be located before the first of the filenames specified on
+the command line (for example, a subsequent
+.IR ex
+.BR next
+command shall edit the first filename from the command line). If the
+.BR \-t
+option was not specified, the current argument list reference shall be
+to the first of the filenames on the command line.
+.SS "Addressing in ex"
+.P
+Addressing in
+.IR ex
+relates to the current line and the current column; the address of a
+line is its 1-based line number, the address of a column is its 1-based
+count from the beginning of the line. Generally, the current line is
+the last line affected by a command. The current line number is the
+address of the current line. In each command description, the effect of
+the command on the current line number and the current column is
+described.
+.P
+Addresses are constructed as follows:
+.IP " 1." 4
+The character
+.BR '.' 
+(period) shall address the current line.
+.IP " 2." 4
+The character
+.BR '$' 
+shall address the last line of the edit buffer.
+.IP " 3." 4
+The positive decimal number
+.IR n
+shall address the
+.IR n th
+line of the edit buffer.
+.IP " 4." 4
+The address
+.BR \(dq\(aqx\(dq 
+refers to the line marked with the mark name character
+.BR 'x' ,
+which shall be a lowercase letter from the portable character set,
+the backquote character, or the single-quote character. It shall be an
+error if the line that was marked is not currently present in the edit
+buffer or the mark has not been set. Lines can be marked with the
+.IR ex
+.BR mark
+or
+.BR k
+commands, or the
+.IR vi
+.BR m
+command.
+.IP " 5." 4
+A regular expression enclosed by
+<slash>
+characters (\c
+.BR '/' )
+shall address the first line found by searching forwards from the line
+following the current line toward the end of the edit buffer and
+stopping at the first line for which the line excluding the terminating
+<newline>
+matches the regular expression. As stated in
+.IR "Regular Expressions in ex",
+an address consisting of a null regular expression delimited by
+<slash>
+characters (\c
+.BR \(dq//\(dq )
+shall address the next line for which the line excluding the
+terminating
+<newline>
+matches the last regular expression encountered. In addition, the second
+<slash>
+can be omitted at the end of a command line. If the
+.BR wrapscan
+edit option is set, the search shall wrap around to the beginning of
+the edit buffer and continue up to and including the current line, so
+that the entire edit buffer is searched. Within the regular expression,
+the sequence
+.BR \(dq\e/\(dq 
+shall represent a literal
+<slash>
+instead of the regular expression delimiter.
+.IP " 6." 4
+A regular expression enclosed in
+<question-mark>
+characters (\c
+.BR '?' )
+shall address the first line found by searching backwards from the line
+preceding the current line toward the beginning of the edit buffer and
+stopping at the first line for which the line excluding the terminating
+<newline>
+matches the regular expression. An address consisting of a null regular
+expression delimited by
+<question-mark>
+characters (\c
+.BR \(dq??\(dq )
+shall address the previous line for which the line excluding the
+terminating
+<newline>
+matches the last regular expression encountered. In addition, the second
+<question-mark>
+can be omitted at the end of a command line. If the
+.BR wrapscan
+edit option is set, the search shall wrap around from the beginning of
+the edit buffer to the end of the edit buffer and continue up to and
+including the current line, so that the entire edit buffer is
+searched. Within the regular expression, the sequence
+.BR \(dq\e?\(dq 
+shall represent a literal
+<question-mark>
+instead of the RE delimiter.
+.IP " 7." 4
+A
+<plus-sign>
+(\c
+.BR '\(pl' )
+or a
+<hyphen-minus>
+(\c
+.BR '\-' )
+followed by a decimal number shall address the current line plus or
+minus the number. A
+.BR '\(pl' 
+or
+.BR '\-' 
+not followed by a decimal number shall address the current line plus or
+minus 1.
+.P
+Addresses can be followed by zero or more address offsets, optionally
+<blank>-separated.
+Address offsets are constructed as follows:
+.IP " 1." 4
+A
+.BR '\(pl' 
+or
+.BR '\-' 
+immediately followed by a decimal number shall add (subtract) the
+indicated number of lines to (from) the address. A
+.BR '\(pl' 
+or
+.BR '\-' 
+not followed by a decimal number shall add (subtract) 1 to (from) the
+address.
+.IP " 2." 4
+A decimal number shall add the indicated number of lines to the
+address.
+.P
+It shall not be an error for an intermediate address value to be less
+than zero or greater than the last line in the edit buffer. It shall be
+an error for the final address value to be less than zero or greater
+than the last line in the edit buffer.
+.P
+Commands take zero, one, or two addresses; see the descriptions of
+.IR 1addr
+and
+.IR 2addr
+in
+.IR "Command Descriptions in ex".
+If more than the required number of addresses are provided to a command
+that requires zero addresses, it shall be an error. Otherwise, if more
+than the required number of addresses are provided to a command, the
+addresses specified first shall be evaluated and then discarded until
+the maximum number of valid addresses remain.
+.P
+Addresses shall be separated from each other by a
+<comma>
+(\c
+.BR ',' )
+or a
+<semicolon>
+(\c
+.BR ';' ).
+If no address is specified before or after a
+<comma>
+or
+<semicolon>
+separator, it shall be as if the address of the current line was
+specified before or after the separator. In the case of a
+<semicolon>
+separator, the current line (\c
+.BR '.' )
+shall be set to the first address, and only then will the next address
+be calculated. This feature can be used to determine the starting line
+for forwards and backwards searches (see rules 5. and 6.).
+.P
+A
+<percent-sign>
+(\c
+.BR '%' )
+shall be equivalent to entering the two addresses
+.BR \(dq1,$\(dq .
+.P
+Any delimiting
+<blank>
+characters between addresses, address separators, or address offsets
+shall be discarded.
+.SS "Command Line Parsing in ex"
+.P
+The following symbol is used in this and following sections to describe
+parsing behavior:
+.IP "\fIescape\fP" 10
+If a character is referred to as ``\c
+<backslash>-escaped''
+or ``\c
+<control>\(hyV-escaped'',
+it shall mean that the character acquired or lost a special
+meaning by virtue of being preceded, respectively, by a
+<backslash>
+or
+<control>\(hyV
+character. Unless otherwise specified, the escaping character shall be
+discarded at that time and shall not be further considered for any
+purpose.
+.P
+Command-line parsing shall be done in the following steps. For each
+step, characters already evaluated shall be ignored; that is, the
+phrase ``leading character'' refers to the next character that has not
+yet been evaluated.
+.IP " 1." 4
+Leading
+<colon>
+characters shall be skipped.
+.IP " 2." 4
+Leading
+<blank>
+characters shall be skipped.
+.IP " 3." 4
+If the leading character is a double-quote character, the characters up
+to and including the next non-\c
+<backslash>-escaped
+<newline>
+shall be discarded, and any subsequent characters shall be parsed as a
+separate command.
+.IP " 4." 4
+Leading characters that can be interpreted as addresses shall be
+evaluated; see
+.IR "Addressing in ex".
+.IP " 5." 4
+Leading
+<blank>
+characters shall be skipped.
+.IP " 6." 4
+If the next character is a
+<vertical-line>
+character or a
+<newline>:
+.RS 4 
+.IP " a." 4
+If the next character is a
+<newline>:
+.RS 4 
+.IP " i." 5
+If
+.IR ex
+is in open or visual mode, the current line shall be set to the last
+address specified, if any.
+.IP ii. 5
+Otherwise, if the last command was terminated by a
+<vertical-line>
+character, no action shall be taken; for example, the command
+.BR \(dq||<newline>\(dq 
+shall execute two implied commands, not three.
+.IP iii. 5
+Otherwise, step 6.b. shall apply.
+.RE
+.IP " b." 4
+Otherwise, the implied command shall be the
+.BR print
+command. The last
+.BR # ,
+.BR p ,
+and
+.BR l
+flags specified to any
+.IR ex
+command shall be remembered and shall apply to this implied command.
+Executing the
+.IR ex
+.BR number ,
+.BR print ,
+or
+.BR list
+command shall set the remembered flags to
+.BR # ,
+nothing, and
+.BR l ,
+respectively, plus any other flags specified for that execution of the
+.BR number ,
+.BR print ,
+or
+.BR list
+command.
+.RS 4 
+.P
+If
+.IR ex
+is not currently performing a
+.BR global
+or
+.BR v
+command, and no address or count is specified, the current line shall
+be incremented by 1 before the command is executed. If incrementing the
+current line would result in an address past the last line in the edit
+buffer, the command shall fail, and the increment shall not happen.
+.RE
+.IP " c." 4
+The
+<newline>
+or
+<vertical-line>
+character shall be discarded and any subsequent characters shall be
+parsed as a separate command.
+.RE
+.IP " 7." 4
+The command name shall be comprised of the next character (if the
+character is not alphabetic), or the next character and any subsequent
+alphabetic characters (if the character is alphabetic), with the
+following exceptions:
+.RS 4 
+.IP " a." 4
+Commands that consist of any prefix of the characters in the command
+name
+.BR delete ,
+followed immediately by any of the characters
+.BR 'l' ,
+.BR 'p' ,
+.BR '\(pl' ,
+.BR '\-' ,
+or
+.BR '#' 
+shall be interpreted as a
+.BR delete
+command, followed by a
+<blank>,
+followed by the characters that were not part of the prefix of the
+.BR delete
+command. The maximum number of characters shall be matched to the
+command name
+.BR delete ;
+for example,
+.BR \(dqdel\(dq 
+shall not be treated as
+.BR \(dqde\(dq 
+followed by the flag
+.BR l .
+.IP " b." 4
+Commands that consist of the character
+.BR 'k' ,
+followed by a character that can be used as the name of a mark, shall
+be equivalent to the mark command followed by a
+<blank>,
+followed by the character that followed the
+.BR 'k' .
+.IP " c." 4
+Commands that consist of the character
+.BR 's' ,
+followed by characters that could be interpreted as valid options to
+the
+.BR s
+command, shall be the equivalent of the
+.BR s
+command, without any pattern or replacement values, followed by a
+<blank>,
+followed by the characters after the
+.BR 's' .
+.RE
+.IP " 8." 4
+The command name shall be matched against the possible command names,
+and a command name that contains a prefix matching the characters
+specified by the user shall be the executed command. In the case of
+commands where the characters specified by the user could be ambiguous,
+the executed command shall be as follows:
+.TS
+center tab(!) box;
+lB | lB || lB | lB || lB | lB.
+a!append!n!next!t!t
+c!change!p!print!u!undo
+ch!change!pr!print!un!undo
+e!edit!r!read!v!v
+m!move!re!read!w!write
+ma!mark!s!s
+.TE
+.RS 4 
+.P
+Implementation extensions with names causing similar ambiguities shall
+not be checked for a match until all possible matches for commands
+specified by POSIX.1\(hy2008 have been checked.
+.RE
+.IP " 9." 4
+If the command is a
+.BR !
+command, or if the command is a
+.BR read
+command followed by zero or more
+<blank>
+characters and a
+.BR ! ,
+or if the command is a
+.BR write
+command followed by one or more
+<blank>
+characters and a
+.BR ! ,
+the rest of the command shall include all characters up to a non-\c
+<backslash>-escaped
+<newline>.
+The
+<newline>
+shall be discarded and any subsequent characters shall be parsed as a
+separate
+.IR ex
+command.
+.IP 10. 4
+Otherwise, if the command is an
+.BR edit ,
+.BR ex ,
+or
+.BR next
+command, or a
+.BR visual
+command while in open or visual mode, the next part of the command
+shall be parsed as follows:
+.RS 4 
+.IP " a." 4
+Any
+.BR '!' 
+character immediately following the command shall be skipped and be
+part of the command.
+.IP " b." 4
+Any leading
+<blank>
+characters shall be skipped and be part of the command.
+.IP " c." 4
+If the next character is a
+.BR '\(pl' ,
+characters up to the first non-\c
+<backslash>-escaped
+<newline>
+or non-\c
+<backslash>-escaped
+<blank>
+shall be skipped and be part of the command.
+.IP " d." 4
+The rest of the command shall be determined by the steps specified in
+paragraph 12.
+.RE
+.IP 11. 4
+Otherwise, if the command is a
+.BR global ,
+.BR open ,
+.BR s ,
+or
+.BR v
+command, the next part of the command shall be parsed as follows:
+.RS 4 
+.IP " a." 4
+Any leading
+<blank>
+characters shall be skipped and be part of the command.
+.IP " b." 4
+If the next character is not an alphanumeric, double-quote,
+<newline>,
+<backslash>,
+or
+<vertical-line>
+character:
+.RS 4 
+.IP " i." 5
+The next character shall be used as a command delimiter.
+.IP ii. 5
+If the command is a
+.BR global ,
+.BR open ,
+or
+.BR v
+command, characters up to the first non-\c
+<backslash>-escaped
+<newline>,
+or first non-\c
+<backslash>-escaped
+delimiter character, shall be skipped and be part of the command.
+.IP iii. 5
+If the command is an
+.BR s
+command, characters up to the first non-\c
+<backslash>-escaped
+<newline>,
+or second non-\c
+<backslash>-escaped
+delimiter character, shall be skipped and be part of the command.
+.RE
+.IP " c." 4
+If the command is a
+.BR global
+or
+.BR v
+command, characters up to the first non-\c
+<backslash>-escaped
+<newline>
+shall be skipped and be part of the command.
+.IP " d." 4
+Otherwise, the rest of the command shall be determined by the steps
+specified in paragraph 12.
+.RE
+.IP 12. 4
+Otherwise:
+.RS 4 
+.IP " a." 4
+If the command was a
+.BR map ,
+.BR unmap ,
+.BR abbreviate ,
+or
+.BR unabbreviate
+command, characters up to the first non-\c
+<control>\(hyV-escaped
+<newline>,
+<vertical-line>,
+or double-quote character shall be skipped and be part of the command.
+.IP " b." 4
+Otherwise, characters up to the first non-\c
+<backslash>-escaped
+<newline>,
+<vertical-line>,
+or double-quote character shall be skipped and be part of the command.
+.IP " c." 4
+If the command was an
+.BR append ,
+.BR change ,
+or
+.BR insert
+command, and the step 12.b. ended at a
+<vertical-line>
+character, any subsequent characters, up to the next non-\c
+<backslash>-escaped
+<newline>
+shall be used as input text to the command.
+.IP " d." 4
+If the command was ended by a double-quote character, all subsequent
+characters, up to the next non-\c
+<backslash>-escaped
+<newline>,
+shall be discarded.
+.IP " e." 4
+The terminating
+<newline>
+or
+<vertical-line>
+character shall be discarded and any subsequent characters shall be
+parsed as a separate
+.IR ex
+command.
+.RE
+.P
+Command arguments shall be parsed as described by the Synopsis and
+Description of each individual
+.IR ex
+command. This parsing shall not be
+<blank>-sensitive,
+except for the
+.BR !
+argument, which must follow the command name without intervening
+<blank>
+characters, and where it would otherwise be ambiguous. For example,
+.IR count
+and
+.IR flag
+arguments need not be
+<blank>-separated
+because
+.BR \(dqd22p\(dq 
+is not ambiguous, but
+.IR file
+arguments to the
+.IR ex
+.BR next
+command must be separated by one or more
+<blank>
+characters. Any
+<blank>
+in command arguments for the
+.BR abbreviate ,
+.BR unabbreviate ,
+.BR map ,
+and
+.BR unmap
+commands can be
+<control>\(hyV-escaped,
+in which case the
+<blank>
+shall not be used as an argument delimiter. Any
+<blank>
+in the command argument for any other command can be
+<backslash>-escaped,
+in which case that
+<blank>
+shall not be used as an argument delimiter.
+.P
+Within command arguments for the
+.BR abbreviate ,
+.BR unabbreviate ,
+.BR map ,
+and
+.BR unmap
+commands, any character can be
+<control>\(hyV-escaped.
+All such escaped characters shall be treated literally and shall have
+no special meaning. Within command arguments for all other
+.IR ex
+commands that are not regular expressions or replacement strings, any
+character that would otherwise have a special meaning can be
+<backslash>-escaped.
+Escaped characters shall be treated literally, without special meaning
+as shell expansion characters or
+.BR '!' ,
+.BR '%' ,
+and
+.BR '#' 
+expansion characters. See
+.IR "Regular Expressions in ex"
+and
+.IR "Replacement Strings in ex"
+for descriptions of command arguments that are regular expressions or
+replacement strings.
+.P
+Non-\c
+<backslash>-escaped
+.BR '%' 
+characters appearing in
+.IR file
+arguments to any
+.IR ex
+command shall be replaced by the current pathname; unescaped
+.BR '#' 
+characters shall be replaced by the alternate pathname. It shall be an
+error if
+.BR '%' 
+or
+.BR '#' 
+characters appear unescaped in an argument and their corresponding
+values are not set.
+.P
+Non-\c
+<backslash>-escaped
+.BR '!' 
+characters in the arguments to either the
+.IR ex
+.BR !
+command or the open and visual mode
+.BR !
+command, or in the arguments to the
+.IR ex
+.BR read
+command, where the first non-\c
+<blank>
+after the command name is a
+.BR '!' 
+character, or in the arguments to the
+.IR ex
+.BR write
+command where the command name is followed by one or more
+<blank>
+characters and the first non-\c
+<blank>
+after the command name is a
+.BR '!' 
+character, shall be replaced with the arguments to the last of those
+three commands as they appeared after all unescaped
+.BR '%' ,
+.BR '#' ,
+and
+.BR '!' 
+characters were replaced. It shall be an error if
+.BR '!' 
+characters appear unescaped in one of these commands and there has been
+no previous execution of one of these commands.
+.P
+If an error occurs during the parsing or execution of an
+.IR ex
+command:
+.IP " *" 4
+An informational message to this effect shall be written. Execution of
+the
+.IR ex
+command shall stop, and the cursor (for example, the current line and
+column) shall not be further modified.
+.IP " *" 4
+If the
+.IR ex
+command resulted from a map expansion, all characters from that map
+expansion shall be discarded, except as otherwise specified by the
+.BR map
+command.
+.IP " *" 4
+Otherwise, if the
+.IR ex
+command resulted from the processing of an
+.IR EXINIT
+environment variable, a
+.BR .exrc
+file, a
+.BR :source
+command, a
+.BR \-c
+option, or a
+.BR + \c
+.IR command
+specified to an
+.IR ex
+.BR edit ,
+.BR ex ,
+.BR next ,
+or
+.BR visual
+command, no further commands from the source of the commands shall be
+executed.
+.IP " *" 4
+Otherwise, if the
+.IR ex
+command resulted from the execution of a buffer or a
+.BR global
+or
+.BR v
+command, no further commands caused by the execution of the buffer or
+the
+.BR global
+or
+.BR v
+command shall be executed.
+.IP " *" 4
+Otherwise, if the
+.IR ex
+command was not terminated by a
+<newline>,
+all characters up to and including the next non-\c
+<backslash>-escaped
+<newline>
+shall be discarded.
+.SS "Input Editing in ex"
+.P
+The following symbol is used in this and the following sections to
+specify command actions:
+.IP "\fIword\fP" 10
+In the POSIX locale, a word consists of a maximal sequence of letters,
+digits, and underscores, delimited at both ends by characters other
+than letters, digits, or underscores, or by the beginning or end of a
+line or the edit buffer.
+.P
+When accepting input characters from the user, in either
+.IR ex
+command mode or
+.IR ex
+text input mode,
+.IR ex
+shall enable canonical mode input processing, as defined in the System Interfaces volume of POSIX.1\(hy2017.
+.br
+.P
+If in
+.IR ex
+text input mode:
+.IP " 1." 4
+If the
+.BR number
+edit option is set,
+.IR ex
+shall prompt for input using the line number that would be assigned to
+the line if it is entered, in the format specified for the
+.IR ex
+.BR number
+command.
+.IP " 2." 4
+If the
+.BR autoindent
+edit option is set,
+.IR ex
+shall prompt for input using
+.BR autoindent
+characters, as described by the
+.BR autoindent
+edit option.
+.BR autoindent
+characters shall follow the line number, if any.
+.P
+If in
+.IR ex
+command mode:
+.IP " 1." 4
+If the
+.BR prompt
+edit option is set, input shall be prompted for using a single
+.BR ':' 
+character; otherwise, there shall be no prompt.
+.P
+The input characters in the following sections shall have the following
+effects on the input line.
+.SS "Scroll"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+eof
+.fi
+.P
+.RE
+.RE
+.P
+See the description of the
+.IR stty
+.IR eof
+character in
+.IR "\fIstty\fR\^".
+.P
+If in
+.IR ex
+command mode:
+.sp
+.RS
+If the
+.IR eof
+character is the first character entered on the line, the line shall be
+evaluated as if it contained two characters: a
+<control>\(hyD
+and a
+<newline>.
+.P
+Otherwise, the
+.IR eof
+character shall have no special meaning.
+.RE
+.br
+.P
+If in
+.IR ex
+text input mode:
+.sp
+.RS
+If the cursor follows an
+.BR autoindent
+character, the
+.BR autoindent
+characters in the line shall be modified so that a part of the next
+text input character will be displayed on the first column in the line
+after the previous
+.BR shiftwidth
+edit option column boundary, and the user shall be prompted again for
+input for the same line.
+.P
+Otherwise, if the cursor follows a
+.BR '0' ,
+which follows an
+.BR autoindent
+character, and the
+.BR '0' 
+was the previous text input character, the
+.BR '0' 
+and all
+.BR autoindent
+characters in the line shall be discarded, and the user shall be
+prompted again for input for the same line.
+.P
+Otherwise, if the cursor follows a
+.BR '\(ha' ,
+which follows an
+.BR autoindent
+character, and the
+.BR '\(ha' 
+was the previous text input character, the
+.BR '\(ha' 
+and all
+.BR autoindent
+characters in the line shall be discarded, and the user shall be
+prompted again for input for the same line. In addition, the
+.BR autoindent
+level for the next input line shall be derived from the same line from
+which the
+.BR autoindent
+level for the current input line was derived.
+.P
+Otherwise, if there are no
+.BR autoindent
+or text input characters in the line, the
+.IR eof
+character shall be discarded.
+.P
+Otherwise, the
+.IR eof
+character shall have no special meaning.
+.RE
+.SS "<newline>"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+<newline>
+.br
+<control>-J
+.fi
+.P
+.RE
+.RE
+.P
+If in
+.IR ex
+command mode:
+.sp
+.RS
+Cause the command line to be parsed;
+<control>\(hyJ
+shall be mapped to the
+<newline>
+for this purpose.
+.RE
+.br
+.P
+If in
+.IR ex
+text input mode:
+.sp
+.RS
+Terminate the current line. If there are no characters other than
+.BR autoindent
+characters on the line, all characters on the line shall be discarded.
+.P
+Prompt for text input on a new line after the current line. If the
+.BR autoindent
+edit option is set, an appropriate number of
+.BR autoindent
+characters shall be added as a prefix to the line as described by the
+.IR ex
+.BR autoindent
+edit option.
+.RE
+.SS "<backslash>"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+<backslash>
+.fi
+.P
+.RE
+.RE
+.P
+Allow the entry of a subsequent
+<newline>
+or
+<control>\(hyJ
+as a literal character, removing any special meaning that it may have
+to the editor during text input mode. The
+<backslash>
+character shall be retained and evaluated when the command line is
+parsed, or retained and included when the input text becomes part of
+the edit buffer.
+.SS "<control>\(hyV"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+<control>-V
+.fi
+.P
+.RE
+.RE
+.P
+Allow the entry of any subsequent character as a literal character,
+removing any special meaning that it may have to the editor during text
+input mode. The
+<control>\(hyV
+character shall be discarded before the command line is parsed or the
+input text becomes part of the edit buffer.
+.P
+If the ``literal next'' functionality is performed by the underlying
+system, it is implementation-defined whether a character other than
+<control>\(hyV
+performs this function.
+.SS "<control>\(hyW"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+<control>-W
+.fi
+.P
+.RE
+.RE
+.P
+Discard the
+<control>\(hyW,
+and the word previous to it in the input line, including any
+<blank>
+characters following the word and preceding the
+<control>\(hyW.
+If the ``word erase'' functionality is performed by the underlying
+system, it is implementation-defined whether a character other than
+<control>\(hyW
+performs this function.
+.SS "Command Descriptions in ex"
+.P
+The following symbols are used in this section to represent command
+modifiers. Some of these modifiers can be omitted, in which case the
+specified defaults shall be used.
+.IP "\fI1addr\fR" 10
+A single line address, given in any of the forms described in
+.IR "Addressing in ex";
+the default shall be the current line (\c
+.BR '.' ),
+unless otherwise specified.
+.RS 10 
+.P
+If the line address is zero, it shall be an error, unless otherwise
+specified in the following command descriptions.
+.P
+If the edit buffer is empty, and the address is specified with a
+command other than
+.BR = ,
+.BR append ,
+.BR insert ,
+.BR open ,
+.BR put ,
+.BR read ,
+or
+.BR visual ,
+or the address is not zero, it shall be an error.
+.RE
+.IP "\fI2addr\fP" 10
+Two addresses specifying an inclusive range of lines. If no addresses
+are specified, the default for
+.IR 2addr
+shall be the current line only (\c
+.BR \(dq.,.\(dq ),
+unless otherwise specified in the following command descriptions. If
+one address is specified,
+.IR 2addr
+shall specify that line only, unless otherwise specified in the
+following command descriptions.
+.RS 10 
+.P
+It shall be an error if the first address is greater than the second
+address.
+.P
+If the edit buffer is empty, and the two addresses are specified with a
+command other than the
+.BR ! ,
+.BR write ,
+.BR wq ,
+or
+.BR xit
+commands, or either address is not zero, it shall be an error.
+.RE
+.IP "\fIcount\fP" 10
+A positive decimal number. If
+.IR count
+is specified, it shall be equivalent to specifying an additional
+address to the command, unless otherwise specified by the following
+command descriptions. The additional address shall be equal to the last
+address specified to the command (either explicitly or by default) plus
+.IR count \-1.
+.RS 10 
+.P
+If this would result in an address greater than the last line of the
+edit buffer, it shall be corrected to equal the last line of the edit
+buffer.
+.RE
+.IP "\fIflags\fP" 10
+One or more of the characters
+.BR '\(pl' ,
+.BR '\-' ,
+.BR '#' ,
+.BR 'p' ,
+or
+.BR 'l' 
+(ell). The flag characters can be
+<blank>-separated,
+and in any order or combination. The characters
+.BR '#' ,
+.BR 'p' ,
+and
+.BR 'l' 
+shall cause lines to be written in the format specified by the
+.BR print
+command with the specified
+.IR flags .
+.RS 10 
+.P
+The lines to be written are as follows:
+.IP " 1." 4
+All edit buffer lines written during the execution of the
+.IR ex
+.BR & ,
+.BR ~ ,
+.BR list ,
+.BR number ,
+.BR open ,
+.BR print ,
+.BR s ,
+.BR visual ,
+and
+.BR z
+commands shall be written as specified by
+.IR flags .
+.IP " 2." 4
+After the completion of an
+.IR ex
+command with a flag as an argument, the current line shall be written
+as specified by
+.IR flags ,
+unless the current line was the last line written by the command.
+.P
+The characters
+.BR '\(pl' 
+and
+.BR '\-' 
+cause the value of the current line after the execution of the
+.IR ex
+command to be adjusted by the offset address as described in
+.IR "Addressing in ex".
+This adjustment shall occur before the current line is written as
+described in 2. above.
+.P
+The default for
+.IR flags
+shall be none.
+.RE
+.IP "\fIbuffer\fP" 10
+One of a number of named areas for holding text. The named buffers are
+specified by the alphanumeric characters of the POSIX locale. There
+shall also be one ``unnamed'' buffer. When no buffer is specified for
+editor commands that use a buffer, the unnamed buffer shall be used.
+Commands that store text into buffers shall store the text as it was
+before the command took effect, and shall store text occurring earlier
+in the file before text occurring later in the file, regardless of how
+the text region was specified. Commands that store text into buffers
+shall store the text into the unnamed buffer as well as any specified
+buffer.
+.RS 10 
+.P
+In
+.IR ex
+commands, buffer names are specified as the name by itself. In open or
+visual mode commands the name is preceded by a double-quote (\c
+.BR '\&"' )
+character.
+.P
+If the specified buffer name is an uppercase character, and the buffer
+contents are to be modified, the buffer shall be appended to rather
+than being overwritten. If the buffer is not being modified, specifying
+the buffer name in lowercase and uppercase shall have identical
+results.
+.P
+There shall also be buffers named by the numbers 1 through 9. In open
+and visual mode, if a region of text including characters from more
+than a single line is being modified by the
+.IR vi
+.BR c
+or
+.BR d
+commands, the motion character associated with the
+.BR c
+or
+.BR d
+commands specifies that the buffer text shall be in line mode, or the
+commands
+.BR % ,
+.BR ` ,
+.BR / ,
+.BR ? ,
+.BR ( ,
+.BR ) ,
+.BR N ,
+.BR n ,
+.BR { ,
+or
+.BR }
+are used to define a region of text for the
+.BR c
+or
+.BR d
+commands, the contents of buffers 1 through 8 shall be moved into the
+buffer named by the next numerically greater value, the contents of
+buffer 9 shall be discarded, and the region of text shall be copied
+into buffer 1. This shall be in addition to copying the text into a
+user-specified buffer or unnamed buffer, or both. Numeric buffers can
+be specified as a source buffer for open and visual mode commands;
+however, specifying a numeric buffer as the write target of an open or
+visual mode command shall have unspecified results.
+.P
+The text of each buffer shall have the characteristic of being in
+either line or character mode. Appending text to a non-empty buffer
+shall set the mode to match the characteristic of the
+text being appended. Appending text to a buffer shall cause the
+creation of at least one additional line in the buffer. All text stored
+into buffers by
+.IR ex
+commands shall be in line mode. The
+.IR ex
+commands that use buffers as the source of text specify individually
+how buffers of different modes are handled. Each open or visual mode
+command that uses buffers for any purpose specifies individually the
+mode of the text stored into the buffer and how buffers of different
+modes are handled.
+.RE
+.IP "\fIfile\fP" 10
+Command text used to derive a pathname. The default shall be the
+current pathname, as defined previously, in which case, if no current
+pathname has yet been established it shall be an error, except where
+specifically noted in the individual command descriptions that follow.
+If the command text contains any of the characters
+.BR '\(ti' ,
+.BR '{' ,
+.BR '[' ,
+.BR '*' ,
+.BR '?' ,
+.BR '$' ,
+.BR '\&"' ,
+backquote, single-quote, and
+<backslash>,
+it shall be subjected to the process of ``shell expansions'', as
+described below; if more than a single pathname results and the
+command expects only one, it shall be an error.
+.RS 10 
+.P
+The process of shell expansions in the editor shall be done as
+follows. The
+.IR ex
+utility shall pass two arguments to the program named by the shell edit
+option; the first shall be
+.BR \-c ,
+and the second shall be the string
+.BR \(dqecho\(dq 
+and the command text as a single argument. The standard output and
+standard error of that command shall replace the command text.
+.RE
+.IP "\fB!\fP" 10
+A character that can be appended to the command name to modify its
+operation, as detailed in the individual command descriptions. With the
+exception of the
+.IR ex
+.BR read ,
+.BR write ,
+and
+.BR !
+commands, the
+.BR '!' 
+character shall only act as a modifier if there are no
+<blank>
+characters between it and the command name.
+.IP "\fIremembered\ search\ direction\fP" 10
+.br
+The
+.IR vi
+commands
+.BR N
+and
+.BR n
+begin searching in a forwards or backwards direction in the edit buffer
+based on a remembered search direction, which is initially unset, and
+is set by the
+.IR ex
+.BR global ,
+.BR v ,
+.BR s ,
+and
+.BR tag
+commands, and the
+.IR vi
+.BR /
+and
+.BR ?
+commands.
+.SS "Abbreviate"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+ab\fB[\fIbreviate\fB][\fIlhs rhs\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If
+.IR lhs
+and
+.IR rhs
+are not specified, write the current list of abbreviations and do
+nothing more.
+.P
+Implementations may restrict the set of characters accepted in
+.IR lhs
+or
+.IR rhs ,
+except that printable characters and
+<blank>
+characters shall not be restricted. Additional restrictions shall be
+implementation-defined.
+.P
+In both
+.IR lhs
+and
+.IR rhs ,
+any character may be escaped with a
+<control>\(hyV,
+in which case the character shall not be used to delimit
+.IR lhs
+from
+.IR rhs ,
+and the escaping
+<control>\(hyV
+shall be discarded.
+.P
+In open and visual text input mode, if a non-word or
+<ESC>
+character that is not escaped by a
+<control>\(hyV
+character is entered after a word character, a check shall be made for
+a set of characters matching
+.IR lhs ,
+in the text input entered during this command. If it is found, the
+effect shall be as if
+.IR rhs
+was entered instead of
+.IR lhs .
+.P
+The set of characters that are checked is defined as follows:
+.IP " 1." 4
+If there are no characters inserted before the word and non-word or
+<ESC>
+characters that triggered the check, the set of characters shall
+consist of the word character.
+.IP " 2." 4
+If the character inserted before the word and non-word or
+<ESC>
+characters that triggered the check is a word character, the set of
+characters shall consist of the characters inserted immediately before
+the triggering characters that are word characters, plus the triggering
+word character.
+.IP " 3." 4
+If the character inserted before the word and non-word or
+<ESC>
+characters that triggered the check is not a word character, the set of
+characters shall consist of the characters that were inserted before
+the triggering characters that are neither
+<blank>
+characters nor word characters, plus the triggering word character.
+.P
+It is unspecified whether the
+.IR lhs
+argument entered for the
+.IR ex
+.BR abbreviate
+and
+.BR unabbreviate
+commands is replaced in this fashion. Regardless of whether or not the
+replacement occurs, the effect of the command shall be as if the
+replacement had not occurred.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Append"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fRa\fB[\fRppend\fB][\fR!\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Enter
+.IR ex
+text input mode; the input text shall be placed after the specified
+line. If line zero is specified, the text shall be placed at the
+beginning of the edit buffer.
+.P
+This command shall be affected by the
+.BR number
+and
+.BR autoindent
+edit options; following the command name with
+.BR '!' 
+shall cause the
+.BR autoindent
+edit option setting to be toggled for the duration of this command
+only.
+.P
+.IR "Current line" :
+Set to the last input line; if no lines were input, set to the
+specified line, or to the first line of the edit buffer if a line of
+zero was specified, or zero if the edit buffer is empty.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Arguments"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+ar\fB[\fIgs\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Write the current argument list, with the current argument-list entry,
+if any, between
+.BR '[' 
+and
+.BR ']' 
+characters.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Change"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRc\fB[\fRhange\fB][\fR!\fB][\fIcount\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Enter
+.IR ex
+text input mode; the input text shall replace the specified lines. The
+specified lines shall be copied into the unnamed buffer, which shall
+become a line mode buffer.
+.P
+This command shall be affected by the
+.BR number
+and
+.BR autoindent
+edit options; following the command name with
+.BR '!' 
+shall cause the
+.BR autoindent
+edit option setting to be toggled for the duration of this command
+only.
+.P
+.IR "Current line" :
+Set to the last input line; if no lines were input, set to the line
+before the first address, or to the first line of the edit buffer if
+there are no lines preceding the first address, or to zero if the edit
+buffer is empty.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Change Directory"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+chd\fB[\fRir\fB][\fR!\fB][\fIdirectory\fB]\fR
+cd\fB[\fR!\fB][\fIdirectory\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Change the current working directory to
+.IR directory .
+.P
+If no
+.IR directory
+argument is specified, and the
+.IR HOME
+environment variable is set to a non-null and non-empty value,
+.IR directory
+shall default to the value named in the
+.IR HOME
+environment variable. If the
+.IR HOME
+environment variable is empty or is undefined, the default value of
+.IR directory
+is implementation-defined.
+.P
+If no
+.BR '!' 
+is appended to the command name, and the edit buffer has been modified
+since the last complete write, and the current pathname does not begin
+with a
+.BR '/' ,
+it shall be an error.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Copy"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRco\fB[\fRpy\fB] \fI1addr \fB[\fIflags\fB]
+[\fI2addr\fB] \fRt \fI1addr \fB[\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Copy the specified lines after the specified destination line; line
+zero specifies that the lines shall be placed at the beginning of the
+edit buffer.
+.P
+.IR "Current line" :
+Set to the last line copied.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Delete"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRd\fB[\fRelete\fB][\fIbuffer\fB][\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Delete the specified lines into a buffer (defaulting to the unnamed
+buffer), which shall become a line-mode buffer.
+.P
+Flags can immediately follow the command name; see
+.IR "Command Line Parsing in ex".
+.P
+.IR "Current line" :
+Set to the line following the deleted lines, or to the last line in the
+edit buffer if that line is past the end of the edit buffer, or to zero
+if the edit buffer is empty.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Edit"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+e\fB[\fRdit\fB][\fR!\fB][\fR+\fIcommand\fB][\fIfile\fB]\fR
+ex\fB[\fR!\fB][\fR+\fIcommand\fB][\fIfile\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If no
+.BR '!' 
+is appended to the command name, and the edit buffer has been modified
+since the last complete write, it shall be an error.
+.P
+If
+.IR file
+is specified, replace the current contents of the edit buffer with the
+current contents of
+.IR file ,
+and set the current pathname to
+.IR file .
+If
+.IR file
+is not specified, replace the current contents of the edit buffer with
+the current contents of the file named by the current pathname. If for
+any reason the current contents of the file cannot be accessed, the
+edit buffer shall be empty.
+.P
+The
+.BR + \c
+.IR command
+option shall be
+<blank>-delimited;
+<blank>
+characters within the
+.BR + \c
+.IR command
+can be escaped by preceding them with a
+<backslash>
+character. The
+.BR + \c
+.IR command
+shall be interpreted as an
+.IR ex
+command immediately after the contents of the edit buffer have been
+replaced and the current line and column have been set.
+.P
+If the edit buffer is empty:
+.P
+.IR "Current line" :
+Set to 0.
+.P
+.IR "Current column" :
+Set to 1.
+.P
+Otherwise, if executed while in
+.IR ex
+command mode or if the
+.BR + \c
+.IR command
+argument is specified:
+.P
+.IR "Current line" :
+Set to the last line of the edit buffer.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.P
+Otherwise, if
+.IR file
+is omitted or results in the current pathname:
+.P
+.IR "Current line" :
+Set to the first line of the edit buffer.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.P
+Otherwise, if
+.IR file
+is the same as the last file edited, the line and column shall be set
+as follows; if the file was previously edited, the line and column may
+be set as follows:
+.P
+.IR "Current line" :
+Set to the last value held when that file was last edited. If this
+value is not a valid line in the new edit buffer, set to the first line
+of the edit buffer.
+.P
+.IR "Current column" :
+If the current line was set to the last value held when the file was
+last edited, set to the last value held when the file was last edited.
+Otherwise, or if the last value is not a valid column in the new edit
+buffer, set to non-\c
+<blank>.
+.br
+.P
+Otherwise:
+.P
+.IR "Current line" :
+Set to the first line of the edit buffer.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "File"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+f\fB[\fRile\fB][\fIfile\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If a
+.IR file
+argument is specified, the alternate pathname shall be set to the
+current pathname, and the current pathname shall be set to
+.IR file .
+.P
+Write an informational message. If the file has a current pathname, it
+shall be included in this message; otherwise, the message shall
+indicate that there is no current pathname. If the edit buffer
+contains lines, the current line number and the number of lines in the
+edit buffer shall be included in this message; otherwise, the message
+shall indicate that the edit buffer is empty. If the edit buffer has
+been modified since the last complete write, this fact shall be
+included in this message. If the
+.BR readonly
+edit option is set, this fact shall be included in this message. The
+message may contain other unspecified information.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Global"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRg\fB[\fRlobal\fB] \fR/\fIpattern\fR/ \fB[\fIcommands\fB]
+[\fI2addr\fB] \fRv /\fIpattern\fR/ \fB[\fIcommands\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+The optional
+.BR '!' 
+character after the
+.BR global
+command shall be the same as executing the
+.BR v
+command.
+.P
+If
+.IR pattern
+is empty (for example,
+.BR \(dq//\(dq )
+or not specified, the last regular expression used in the editor
+command shall be used as the
+.IR pattern .
+The
+.IR pattern
+can be delimited by
+<slash>
+characters (shown in the Synopsis), as well as any non-alphanumeric
+or non-\c
+<blank>
+other than
+<backslash>,
+<vertical-line>,
+<newline>,
+or double-quote.
+.P
+If no lines are specified, the lines shall default to the entire file.
+.P
+The
+.BR global
+and
+.BR v
+commands are logically two-pass operations. First, mark the lines
+within the specified lines for which the line excluding the terminating
+<newline>
+matches (\c
+.BR global )
+or does not match (\c
+.BR v
+or
+.BR global! )
+the specified pattern. Second, execute the
+.IR ex
+commands given by
+.IR commands ,
+with the current line (\c
+.BR '.' )
+set to each marked line. If an error occurs during this process, or the
+contents of the edit buffer are replaced (for example, by the
+.IR ex
+.BR :edit
+command) an error message shall be written and no more commands
+resulting from the execution of this command shall be processed.
+.P
+Multiple
+.IR ex
+commands can be specified by entering multiple commands on a single
+line using a
+<vertical-line>
+to delimit them, or one per line, by escaping each
+<newline>
+with a
+<backslash>.
+.P
+If no commands are specified:
+.IP " 1." 4
+If in
+.IR ex
+command mode, it shall be as if the
+.BR print
+command were specified.
+.IP " 2." 4
+Otherwise, no command shall be executed.
+.P
+For the
+.BR append ,
+.BR change ,
+and
+.BR insert
+commands, the input text shall be included as part of the command, and
+the terminating
+<period>
+can be omitted if the command ends the list of commands. The
+.BR open
+and
+.BR visual
+commands can be specified as one of the commands, in which case each
+marked line shall cause the editor to enter open or visual mode. If
+open or visual mode is exited using the
+.IR vi
+.BR Q
+command, the current line shall be set to the next marked line, and
+open or visual mode reentered, until the list of marked lines is
+exhausted.
+.P
+The
+.BR global ,
+.BR v ,
+and
+.BR undo
+commands cannot be used in
+.IR commands .
+Marked lines may be deleted by commands executed for lines occurring
+earlier in the file than the marked lines. In this case, no commands
+shall be executed for the deleted lines.
+.P
+If the remembered search direction is not set, the
+.BR global
+and
+.BR v
+commands shall set it to forward.
+.P
+The
+.BR autoprint
+and
+.BR autoindent
+edit options shall be inhibited for the duration of the
+.BR g
+or
+.BR v
+command.
+.P
+.IR "Current line" :
+If no commands executed, set to the last marked line. Otherwise, as
+specified for the executed
+.IR ex
+commands.
+.P
+.IR "Current column" :
+If no commands are executed, set to non-\c
+<blank>;
+otherwise, as specified for the individual
+.IR ex
+commands.
+.SS "Insert"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fRi\fB[\fRnsert\fB][\fR!\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Enter
+.IR ex
+text input mode; the input text shall be placed before the specified
+line. If the line is zero or 1, the text shall be placed at the
+beginning of the edit buffer.
+.P
+This command shall be affected by the
+.BR number
+and
+.BR autoindent
+edit options; following the command name with
+.BR '!' 
+shall cause the
+.BR autoindent
+edit option setting to be toggled for the duration of this command
+only.
+.P
+.IR "Current line" :
+Set to the last input line; if no lines were input, set to the line
+before the specified line, or to the first line of the edit buffer if
+there are no lines preceding the specified line, or zero if the edit
+buffer is empty.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Join"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRj\fB[\fRoin\fB][\fR!\fB][\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If
+.IR count
+is specified:
+.sp
+.RS
+If no address was specified, the
+.BR join
+command shall behave as if
+.IR 2addr
+were the current line and the current line plus
+.IR count
+(.\|,\|. +
+.IR count ).
+.P
+If one address was specified, the
+.BR join
+command shall behave as if
+.IR 2addr
+were the specified address and the specified address plus
+.IR count
+(\c
+.IR addr ,\c
+.IR addr
++
+.IR count ).
+.P
+If two addresses were specified, the
+.BR join
+command shall behave as if an additional address, equal to the last
+address plus
+.IR count
+\-1 (\c
+.IR addr1 ,\c
+.IR addr2 ,\c
+.IR addr2
++
+.IR count
+\-1), was specified.
+.P
+If this would result in a second address greater than the last line of
+the edit buffer, it shall be corrected to be equal to the last line of
+the edit buffer.
+.RE
+.P
+If no
+.IR count
+is specified:
+.sp
+.RS
+If no address was specified, the
+.BR join
+command shall behave as if
+.IR 2addr
+were the current line and the next line (.\|,\|. +1).
+.P
+If one address was specified, the
+.BR join
+command shall behave as if
+.IR 2addr
+were the specified address and the next line (\c
+.IR addr ,\c
+.IR addr
++1).
+.RE
+.P
+Join the text from the specified lines together into a single line,
+which shall replace the specified lines.
+.P
+If a
+.BR '!' 
+character is appended to the command name, the
+.BR join
+shall be without modification of any line, independent of the current
+locale.
+.P
+Otherwise, in the POSIX locale, set the current line to the first of
+the specified lines, and then, for each subsequent line, proceed as
+follows:
+.IP " 1." 4
+Discard leading
+<space>
+characters from the line to be joined.
+.IP " 2." 4
+If the line to be joined is now empty, delete it, and skip steps 3
+through 5.
+.IP " 3." 4
+If the current line ends in a
+<blank>,
+or the first character of the line to be joined is a
+.BR ')' 
+character, join the lines without further modification.
+.IP " 4." 4
+If the last character of the current line is a
+.BR '.' ,
+join the lines with two
+<space>
+characters between them.
+.IP " 5." 4
+Otherwise, join the lines with a single
+<space>
+between them.
+.P
+.IR "Current line" :
+Set to the first line specified.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "List"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRl\fB[\fRist\fB][\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+This command shall be equivalent to the
+.IR ex
+command:
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRp\fB[\fRrint\fB][\fIcount\fB] \fRl\fB[\fIflags\fB]\fR
+.fi
+.P
+.RE
+.P
+See
+.IR "Print".
+.SS "Map"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+map\fB[\fR!\fB][\fIlhs rhs\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If
+.IR lhs
+and
+.IR rhs
+are not specified:
+.IP " 1." 4
+If
+.BR '!' 
+is specified, write the current list of text input mode maps.
+.IP " 2." 4
+Otherwise, write the current list of command mode maps.
+.IP " 3." 4
+Do nothing more.
+.P
+Implementations may restrict the set of characters accepted in
+.IR lhs
+or
+.IR rhs ,
+except that printable characters and
+<blank>
+characters shall not be restricted. Additional restrictions shall be
+implementation-defined. In both
+.IR lhs
+and
+.IR rhs ,
+any character can be escaped with a
+<control>\(hyV,
+in which case the character shall not be used to delimit
+.IR lhs
+from
+.IR rhs ,
+and the escaping
+<control>\(hyV
+shall be discarded.
+.P
+If the character
+.BR '!' 
+is appended to the
+.BR map
+command name, the mapping shall be effective during open or visual text
+input mode rather than
+.BR open
+or
+.BR visual
+command mode. This allows
+.IR lhs
+to have two different
+.BR map
+definitions at the same time: one for command mode and one for text
+input mode.
+.br
+.P
+For command mode mappings:
+.sp
+.RS
+When the
+.IR lhs
+is entered as any part of a
+.IR vi
+command in open or visual mode (but not as part of the arguments to the
+command), the action shall be as if the corresponding
+.IR rhs
+had been entered.
+.P
+If any character in the command, other than the first, is escaped using
+a
+<control>\(hyV
+character, that character shall not be part of a match to an
+.IR lhs .
+.P
+It is unspecified whether implementations shall support
+.BR map
+commands where the
+.IR lhs
+is more than a single character in length, where the first character of
+the
+.IR lhs
+is printable.
+.RE
+.P
+.sp
+.RS
+If
+.IR lhs
+contains more than one character and the first character is
+.BR '#' ,
+followed by a sequence of digits corresponding to a numbered function
+key, then when this function key is typed it shall be mapped to
+.IR rhs .
+Characters other than digits following a
+.BR '#' 
+character also represent the function key named by the characters in
+the
+.IR lhs
+following the
+.BR '#' 
+and may be mapped to
+.IR rhs .
+It is unspecified how function keys are named or what function keys are
+supported.
+.RE
+.P
+For text input mode mappings:
+.sp
+.RS
+When the
+.IR lhs
+is entered as any part of text entered in open or visual text input
+modes, the action shall be as if the corresponding
+.IR rhs
+had been entered.
+.P
+If any character in the input text is escaped using a
+<control>\(hyV
+character, that character shall not be part of a match to an
+.IR lhs .
+.P
+It is unspecified whether the
+.IR lhs
+text entered for subsequent
+.BR map
+or
+.BR unmap
+commands is replaced with the
+.IR rhs
+text for the purposes of the screen display; regardless of whether or
+not the display appears as if the corresponding
+.IR rhs
+text was entered, the effect of the command shall be as if the
+.IR lhs
+text was entered.
+.RE
+.P
+If only part of the
+.IR lhs
+is entered, it is unspecified how long the editor will wait for
+additional, possibly matching characters before treating the already
+entered characters as not matching the
+.IR lhs .
+.P
+The
+.IR rhs
+characters shall themselves be subject to remapping, unless otherwise
+specified by the
+.BR remap
+edit option, except that if the characters in
+.IR lhs
+occur as prefix characters in
+.IR rhs ,
+those characters shall not be remapped.
+.P
+On block-mode terminals, the mapping need not occur immediately (for
+example, it may occur after the terminal transmits a group of
+characters to the system), but it shall achieve the same results as if
+it occurred immediately.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Mark"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fRma\fB[\fRrk\fB] \fIcharacter
+\fB[\fI1addr\fB] \fRk \fIcharacter\fR
+.fi
+.P
+.RE
+.RE
+.P
+Implementations shall support
+.IR character
+values of a single lowercase letter of the POSIX locale and the
+backquote and single-quote characters; support of other characters is
+implementation-defined.
+.P
+If executing the
+.IR vi
+.BR m
+command, set the specified mark to the current line and 1-based
+numbered character referenced by the current column, if any; otherwise,
+column position 1.
+.P
+Otherwise, set the specified mark to the specified line and 1-based
+numbered first non-\c
+<blank>
+non-\c
+<newline>
+in the line, if any; otherwise, the last non-\c
+<newline>
+in the line, if any; otherwise, column position 1.
+.P
+The mark shall remain associated with the line until the mark is reset
+or the line is deleted. If a deleted line is restored by a subsequent
+.BR undo
+command, any marks previously associated with the line, which have not
+been reset, shall be restored as well. Any use of a mark not associated
+with a current line in the edit buffer shall be an error.
+.P
+The marks
+.BR `
+and
+.BR \(aq
+shall be set as described previously, immediately before the following
+events occur in the editor:
+.IP " 1." 4
+The use of
+.BR '$' 
+as an
+.IR ex
+address
+.IP " 2." 4
+The use of a positive decimal number as an
+.IR ex
+address
+.IP " 3." 4
+The use of a search command as an
+.IR ex
+address
+.IP " 4." 4
+The use of a mark reference as an
+.IR ex
+address
+.IP " 5." 4
+The use of the following open and visual mode commands:
+<control>\(hy],
+.BR % ,
+.BR ( ,
+.BR ) ,
+.BR [ ,
+.BR ] ,
+.BR { ,
+.BR }
+.IP " 6." 4
+The use of the following open and visual mode commands:
+.BR \(aq ,
+.BR G ,
+.BR H ,
+.BR L ,
+.BR M ,
+.BR z
+if the current line will change as a result of the command
+.IP " 7." 4
+The use of the open and visual mode commands:
+.BR / ,
+.BR ? ,
+.BR N ,
+.BR ` ,
+.BR n
+if the current line or column will change as a result of the command
+.IP " 8." 4
+The use of the
+.IR ex
+mode commands:
+.BR z ,
+.BR undo ,
+.BR global ,
+.BR v
+.P
+For rules 1., 2., 3., and 4., the
+.BR `
+and
+.BR \(aq
+marks shall not be set if the
+.IR ex
+command is parsed as specified by rule 6.a. in
+.IR "Command Line Parsing in ex".
+.P
+For rules 5., 6., and 7., the
+.BR `
+and
+.BR \(aq
+marks shall not be set if the commands are used as motion commands in
+open and visual mode.
+.P
+For rules 1., 2., 3., 4., 5., 6., 7., and 8., the
+.BR `
+and
+.BR \(aq
+marks shall not be set if the command fails.
+.P
+The
+.BR `
+and
+.BR \(aq
+marks shall be set as described previously, each time the contents of
+the edit buffer are replaced (including the editing of the initial
+buffer), if in open or visual mode, or if in
+.BR ex
+mode and the edit buffer is not empty, before any commands or movements
+(including commands or movements specified by the
+.BR \-c
+or
+.BR \-t
+options or the
+.BR + \c
+.IR command
+argument) are executed on the edit buffer. If in open or visual mode,
+the marks shall be set as if executing the
+.IR vi
+.BR m
+command; otherwise, as if executing the
+.IR ex
+.BR mark
+command.
+.P
+When changing from
+.BR ex
+mode to open or visual mode, if the
+.BR `
+and
+.BR \(aq
+marks are not already set, the
+.BR `
+and
+.BR \(aq
+marks shall be set as described previously.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Move"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRm\fB[\fRove\fB] \fI1addr\fR \fB[\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Move the specified lines after the specified destination line. A
+destination of line zero specifies that the lines shall be placed at
+the beginning of the edit buffer. It shall be an error if the
+destination line is within the range of lines to be moved.
+.P
+.IR "Current line" :
+Set to the last of the moved lines.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Next"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+n\fB[\fRext\fB][\fR!\fB][\fR+\fIcommand\fB][\fIfile \fR...\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If no
+.BR '!' 
+is appended to the command name, and the edit buffer has been modified
+since the last complete write, it shall be an error, unless the file is
+successfully written as specified by the
+.BR autowrite
+option.
+.br
+.P
+If one or more files is specified:
+.IP " 1." 4
+Set the argument list to the specified filenames.
+.IP " 2." 4
+Set the current argument list reference to be the first entry in the
+argument list.
+.IP " 3." 4
+Set the current pathname to the first filename specified.
+.P
+Otherwise:
+.IP " 1." 4
+It shall be an error if there are no more filenames in the argument
+list after the filename currently referenced.
+.IP " 2." 4
+Set the current pathname and the current argument list reference to
+the filename after the filename currently referenced in the argument
+list.
+.P
+Replace the contents of the edit buffer with the contents of the file
+named by the current pathname. If for any reason the contents of the
+file cannot be accessed, the edit buffer shall be empty.
+.P
+This command shall be affected by the
+.BR autowrite
+and
+.BR writeany
+edit options.
+.P
+The
+.BR + \c
+.IR command
+option shall be
+<blank>-delimited;
+<blank>
+characters can be escaped by preceding them with a
+<backslash>
+character. The
+.BR + \c
+.IR command
+shall be interpreted as an
+.IR ex
+command immediately after the contents of the edit buffer have been
+replaced and the current line and column have been set.
+.P
+.IR "Current line" :
+Set as described for the
+.BR edit
+command.
+.P
+.IR "Current column" :
+Set as described for the
+.BR edit
+command.
+.SS "Number"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRnu\fB[\fRmber\fB][\fIcount\fB][\fIflags\fB]
+[\fI2addr\fB] \fR#\fB[\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+These commands shall be equivalent to the
+.IR ex
+command:
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRp\fB[\fRrint\fB][\fIcount\fB] \fR#\fB[\fIflags\fB]\fR
+.fi
+.P
+.RE
+.P
+See
+.IR "Print".
+.SS "Open"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fRo\fB[\fRpen\fB]\fR /\fIpattern\fR/ \fB[\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+This command need not be supported on block-mode terminals or terminals
+with insufficient capabilities. If standard input, standard output, or
+standard error are not terminal devices, the results are unspecified.
+.P
+Enter open mode.
+.P
+The trailing delimiter can be omitted from
+.IR pattern
+at the end of the command line. If
+.IR pattern
+is empty (for example,
+.BR \(dq//\(dq )
+or not specified, the last regular expression used in the editor shall
+be used as the pattern. The pattern can be delimited by
+<slash>
+characters (shown in the Synopsis), as well as any alphanumeric, or non-\c
+<blank>
+other than
+<backslash>,
+<vertical-line>,
+<newline>,
+or
+double-quote.
+.P
+.IR "Current line" :
+Set to the specified line.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Preserve"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+pre\fB[\fRserve\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Save the edit buffer in a form that can later be recovered by using the
+.BR \-r
+option or by using the
+.IR ex
+.BR recover
+command. After the file has been preserved, a mail message shall be
+sent to the user. This message shall be readable by invoking the
+.IR mailx
+utility. The message shall contain the name of the file, the time of
+preservation, and an
+.IR ex
+command that could be used to recover the file. Additional information
+may be included in the mail message.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Print"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRp\fB[\fRrint\fB][\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Write the addressed lines. The behavior is unspecified if the number of
+columns on the display is less than the number of columns required to
+write any single character in the lines being written.
+.P
+Non-printable characters, except for the
+<tab>,
+shall be written as implementation-defined multi-character sequences.
+.P
+If the
+.BR #
+flag is specified or the
+.BR number
+edit option is set, each line shall be preceded by its line number in
+the following format:
+.sp
+.RS 4
+.nf
+
+"%6d  ", <\fIline number\fR>
+.fi
+.P
+.RE
+.P
+If the
+.BR l
+flag is specified or the
+.BR list
+edit option is set:
+.IP " 1." 4
+The characters listed in the Base Definitions volume of POSIX.1\(hy2017,
+.IR "Table 5-1" ", " "Escape Sequences and Associated Actions"
+shall be written as the corresponding escape sequence.
+.IP " 2." 4
+Non-printable characters not in the Base Definitions volume of POSIX.1\(hy2017,
+.IR "Table 5-1" ", " "Escape Sequences and Associated Actions"
+shall be written as one three-digit octal number (with a preceding
+<backslash>)
+for each byte in the character (most significant byte first).
+.IP " 3." 4
+The end of each line shall be marked with a
+.BR '$' ,
+and literal
+.BR '$' 
+characters within the line shall be written with a preceding
+<backslash>.
+.P
+Long lines shall be folded; the length at which folding occurs is
+unspecified, but should be appropriate for the output terminal,
+considering the number of columns of the terminal.
+.P
+If a line is folded, and the
+.BR l
+flag is not specified and the
+.BR list
+edit option is not set, it is unspecified whether a multi-column
+character at the folding position is separated; it shall not be
+discarded.
+.P
+.IR "Current line" :
+Set to the last written line.
+.P
+.IR "Current column" :
+Unchanged if the current line is unchanged; otherwise, set to non-\c
+<blank>.
+.SS "Put"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fRpu\fB[\fRt\fB][\fIbuffer\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Append text from the specified buffer (by default, the unnamed buffer)
+to the specified line; line zero specifies that the text shall be
+placed at the beginning of the edit buffer. Each portion of a line in
+the buffer shall become a new line in the edit buffer, regardless of
+the mode of the buffer.
+.P
+.IR "Current line" :
+Set to the last line entered into the edit buffer.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Quit"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+q\fB[\fRuit\fB][\fR!\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If no
+.BR '!' 
+is appended to the command name:
+.IP " 1." 4
+If the edit buffer has been modified since the last complete write, it
+shall be an error.
+.IP " 2." 4
+If there are filenames in the argument list after the filename
+currently referenced, and the last command was not a
+.BR quit ,
+.BR wq ,
+.BR xit ,
+or
+.BR ZZ
+(see
+.IR "Exit")
+command, it shall be an error.
+.P
+Otherwise, terminate the editing session.
+.SS "Read"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fRr\fB[\fRead\fB][\fR!\fB][\fIfile\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If
+.BR '!' 
+is not the first non-\c
+<blank>
+to follow the command name, a copy of the specified file shall be
+appended into the edit buffer after the specified line; line zero
+specifies that the copy shall be placed at the beginning of the edit
+buffer. The number of lines and bytes read shall be written. If no
+.IR file
+is named, the current pathname shall be the default. If there is no
+current pathname, then
+.IR file
+shall become the current pathname. If there is no current pathname or
+.IR file
+operand, it shall be an error. Specifying a
+.IR file
+that is not of type regular shall have unspecified results.
+.P
+Otherwise, if
+.IR file
+is preceded by
+.BR '!' ,
+the rest of the line after the
+.BR '!' 
+shall have
+.BR '%' ,
+.BR '#' ,
+and
+.BR '!' 
+characters expanded as described in
+.IR "Command Line Parsing in ex".
+.P
+The
+.IR ex
+utility shall then pass two arguments to the program named by the
+shell edit option; the first shall be
+.BR \-c
+and the second shall be the expanded arguments to the
+.BR read
+command as a single argument. The standard input of the program shall
+be set to the standard input of the
+.IR ex
+program when it was invoked. The standard error and standard output of
+the program shall be appended into the edit buffer after the specified
+line.
+.P
+Each line in the copied file or program output (as delimited by
+<newline>
+characters or the end of the file or output if it is not immediately
+preceded by a
+<newline>),
+shall be a separate line in the edit buffer. Any occurrences of
+<carriage-return>
+and
+<newline>
+pairs in the output shall be treated as single
+<newline>
+characters.
+.P
+The special meaning of the
+.BR '!' 
+following the
+.BR read
+command can be overridden by escaping it with a
+<backslash>
+character.
+.P
+.IR "Current line" :
+If no lines are added to the edit buffer, unchanged. Otherwise, if in
+open or visual mode, set to the first line entered into the edit
+buffer. Otherwise, set to the last line entered into the edit buffer.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Recover"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+rec\fB[\fRover\fB][\fR!\fB] \fIfile\fR
+.fi
+.P
+.RE
+.RE
+.P
+If no
+.BR '!' 
+is appended to the command name, and the edit buffer has been modified
+since the last complete write, it shall be an error.
+.P
+If no
+.IR file
+operand is specified, then the current pathname shall be used. If
+there is no current pathname or
+.IR file
+operand, it shall be an error.
+.P
+If no recovery information has previously been saved about
+.IR file ,
+the
+.BR recover
+command shall behave identically to the
+.BR edit
+command, and an informational message to this effect shall be written.
+.P
+Otherwise, set the current pathname to
+.IR file ,
+and replace the current contents of the edit buffer with the recovered
+contents of
+.IR file .
+If there are multiple instances of the file to be recovered, the one
+most recently saved shall be recovered, and an informational message
+that there are previous versions of the file that can be recovered
+shall be written. The editor shall behave as if the contents of the
+edit buffer have already been modified.
+.P
+.IR "Current file" :
+Set as described for the
+.BR edit
+command.
+.P
+.IR "Current column" :
+Set as described for the
+.BR edit
+command.
+.SS "Rewind"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+rew\fB[\fRind\fB][\fR!\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If no
+.BR '!' 
+is appended to the command name, and the edit buffer has been modified
+since the last complete write, it shall be an error, unless the file is
+successfully written as specified by the
+.BR autowrite
+option.
+.P
+If the argument list is empty, it shall be an error.
+.P
+The current argument list reference and the current pathname shall be
+set to the first filename in the argument list.
+.P
+Replace the contents of the edit buffer with the contents of the file
+named by the current pathname. If for any reason the contents of the
+file cannot be accessed, the edit buffer shall be empty.
+.P
+This command shall be affected by the
+.BR autowrite
+and
+.BR writeany
+edit options.
+.P
+.IR "Current line" :
+Set as described for the
+.BR edit
+command.
+.P
+.IR "Current column" :
+Set as described for the
+.BR edit
+command.
+.SS "Set"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+se\fB[\fRt\fB][\fIoption\fB[\fR=\fB[\fIvalue\fB]]\fR ...\fB][\fRno\fIoption\fR ...\fB][\fIoption\fR? ...\fB][\fRall\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+When no arguments are specified, write the value of the
+.BR term
+edit option and those options whose values have been changed from the
+default settings; when the argument
+.IR all
+is specified, write all of the option values.
+.P
+Giving an option name followed by the character
+.BR '?' 
+shall cause the current value of that option to be written. The
+.BR '?' 
+can be separated from the option name by zero or more
+<blank>
+characters. The
+.BR '?' 
+shall be necessary only for Boolean valued options. Boolean options can
+be given values by the form
+.BR set
+.IR option
+to turn them on or
+.BR set
+.BR no \c
+.IR option
+to turn them off; string and numeric options can be assigned by the
+form
+.BR set
+.IR option =\c
+.IR value .
+Any
+<blank>
+characters in strings can be included as is by preceding each
+<blank>
+with an escaping
+<backslash>.
+More than one option can be set or listed by a single set command by
+specifying multiple arguments, each separated from the next by one or more
+<blank>
+characters.
+.P
+See
+.IR "Edit Options in ex"
+for details about specific options.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Shell"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+sh\fB[\fRell\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Invoke the program named in the
+.BR shell
+edit option with the single argument
+.BR \-i
+(interactive mode). Editing shall be resumed when the program exits.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Source"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+so\fB[\fRurce\fB] \fIfile\fR
+.fi
+.P
+.RE
+.RE
+.P
+Read and execute
+.IR ex
+commands from
+.IR file .
+Lines in the file that are blank lines shall be ignored.
+.P
+.IR "Current line" :
+As specified for the individual
+.IR ex
+commands.
+.P
+.IR "Current column" :
+As specified for the individual
+.IR ex
+commands.
+.SS "Substitute"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRs\fB[\fRubstitute\fB][\fR/\fIpattern\fR/\fIrepl\fR/\fB[\fIoptions\fB][\fIcount\fB][\fIflags\fB]]\fR
+.br
+\fB[\fI2addr\fB] \fR&\fB[\fIoptions\fB][\fIcount\fB][\fIflags\fB]]\fR
+.br
+\fB[\fI2addr\fB] \fR\(ti\fB[\fIoptions\fB][\fIcount\fB][\fIflags\fB]]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Replace the first instance of the pattern
+.IR pattern
+by the string
+.IR repl
+on each specified line. (See
+.IR "Regular Expressions in ex"
+and
+.IR "Replacement Strings in ex".)
+Any non-alphabetic, non-\c
+<blank>
+delimiter other than
+<backslash>,
+.BR '|' ,
+<newline>,
+or double-quote
+can be used instead of
+.BR '/' .
+<backslash>
+characters can be used to escape delimiters,
+<backslash>
+characters, and other special characters.
+.P
+The trailing delimiter can be omitted from
+.IR pattern
+or from
+.IR repl
+at the end of the command line. If both
+.IR pattern
+and
+.IR repl
+are not specified or are empty (for example,
+.BR \(dq//\(dq ),
+the last
+.BR s
+command shall be repeated. If only
+.IR pattern
+is not specified or is empty, the last regular expression used in the
+editor shall be used as the pattern. If only
+.IR repl
+is not specified or is empty, the pattern shall be replaced by nothing.
+If the entire replacement pattern is
+.BR '%' ,
+the last replacement pattern to an
+.BR s
+command shall be used.
+.P
+Entering a
+<carriage-return>
+in
+.IR repl
+(which requires an escaping
+<backslash>
+in
+.IR ex
+mode and an escaping
+<control>\(hyV
+in open or
+.IR vi
+mode) shall split the line at that point, creating a new line in the
+edit buffer. The
+<carriage-return>
+shall be discarded.
+.P
+If
+.IR options
+includes the letter
+.BR 'g' 
+(\c
+.BR global ),
+all non-overlapping instances of the pattern in the line shall be
+replaced.
+.P
+If
+.IR options
+includes the letter
+.BR 'c' 
+(\c
+.BR confirm ),
+then before each substitution the line shall be written; the written
+line shall reflect all previous substitutions. On the following line,
+<space>
+characters shall be written beneath the characters from the line that
+are before the
+.IR pattern
+to be replaced, and
+.BR '\(ha' 
+characters written beneath the characters included in the
+.IR pattern
+to be replaced. The
+.IR ex
+utility shall then wait for a response from the user. An affirmative
+response shall cause the substitution to be done, while any other input
+shall not make the substitution. An affirmative response shall consist
+of a line with the affirmative response (as defined by the current
+locale) at the beginning of the line. This line shall be subject to
+editing in the same way as the
+.IR ex
+command line.
+.P
+If interrupted (see the ASYNCHRONOUS EVENTS section), any modifications
+confirmed by the user shall be preserved in the edit buffer after the
+interrupt.
+.P
+If the remembered search direction is not set, the
+.BR s
+command shall set it to forward.
+.P
+In the second Synopsis, the
+.BR &
+command shall repeat the previous substitution, as if the
+.BR &
+command were replaced by:
+.sp
+.RS 4
+.nf
+
+s/\fIpattern\fR/\fIrepl\fR/
+.fi
+.P
+.RE
+.P
+where
+.IR pattern
+and
+.IR repl
+are as specified in the previous
+.BR s ,
+.BR & ,
+or
+.BR ~
+command.
+.P
+In the third Synopsis, the
+.BR ~
+command shall repeat the previous substitution, as if the
+.BR '\(ti' 
+were replaced by:
+.sp
+.RS 4
+.nf
+
+s/\fIpattern\fR/\fIrepl\fR/
+.fi
+.P
+.RE
+.P
+where
+.IR pattern
+shall be the last regular expression specified to the editor, and
+.IR repl
+shall be from the previous substitution (including
+.BR &
+and
+.BR ~ )
+command.
+.P
+These commands shall be affected by the
+.IR LC_MESSAGES
+environment variable.
+.P
+.IR "Current line" :
+Set to the last line in which a substitution occurred, or, unchanged if
+no substitution occurred.
+.P
+.IR "Current column":
+Set to non-\c
+<blank>.
+.SS "Suspend"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+su\fB[\fRspend\fB][\fR!\fB]\fR
+st\fB[\fRop\fB][\fR!\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Allow control to return to the invoking process;
+.IR ex
+shall suspend itself as if it had received the SIGTSTP signal. The
+suspension shall occur only if job control is enabled in the invoking
+shell (see the description of
+.IR set
+.BR \-m ).
+.P
+These commands shall be affected by the
+.BR autowrite
+and
+.BR writeany
+edit options.
+.P
+The current
+.BR susp
+character (see
+.IR "\fIstty\fR\^")
+shall be equivalent to the
+.BR suspend
+command.
+.SS "Tag"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+ta\fB[\fRg\fB][\fR!\fB] \fItagstring\fR
+.fi
+.P
+.RE
+.RE
+.P
+The results are unspecified if the format of a tags file is not as
+specified by the
+.IR ctags
+utility (see
+.IR "\fIctags\fR\^")
+description.
+.P
+The
+.BR tag
+command shall search for
+.IR tagstring
+in the tag files referred to by the
+.BR tag
+edit option, in the order they are specified, until a reference to
+.IR tagstring
+is found. Files shall be searched from beginning to end. If no
+reference is found, it shall be an error and an error message to this
+effect shall be written. If the reference is not found, or if an error
+occurs while processing a file referred to in the
+.BR tag
+edit option, it shall be an error, and an error message shall be
+written at the first occurrence of such an error.
+.P
+Otherwise, if the tags file contained a pattern, the pattern shall be
+treated as a regular expression used in the editor; for example, for
+the purposes of the
+.BR s
+command.
+.P
+If the
+.IR tagstring
+is in a file with a different name than the current pathname, set the
+current pathname to the name of that file, and replace the contents of
+the edit buffer with the contents of that file. In this case, if no
+.BR '!' 
+is appended to the command name, and the edit buffer has been modified
+since the last complete write, it shall be an error, unless the file is
+successfully written as specified by the
+.BR autowrite
+option.
+.P
+This command shall be affected by the
+.BR autowrite ,
+.BR tag ,
+.BR taglength ,
+and
+.BR writeany
+edit options.
+.P
+.IR "Current line" :
+If the tags file contained a line number, set to that line number. If
+the line number is larger than the last line in the edit buffer, an
+error message shall be written and the current line shall be set as
+specified for the
+.BR edit
+command.
+.P
+If the tags file contained a pattern, set to the first occurrence of
+the pattern in the file. If no matching pattern is found, an error
+message shall be written and the current line shall be set as specified
+for the
+.BR edit
+command.
+.P
+.IR "Current column" :
+If the tags file contained a line-number reference and that line-number
+was not larger than the last line in the edit buffer, or if the tags
+file contained a pattern and that pattern was found, set to non-\c
+<blank>.
+Otherwise, set as specified for the
+.BR edit
+command.
+.SS "Unabbreviate"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+una\fB[\fRbbrev\fB] \fIlhs\fR
+.fi
+.P
+.RE
+.RE
+.P
+If
+.IR lhs
+is not an entry in the current list of abbreviations (see
+.IR "Abbreviate"),
+it shall be an error. Otherwise, delete
+.IR lhs
+from the list of abbreviations.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Undo"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+u\fB[\fRndo\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Reverse the changes made by the last command that modified the contents
+of the edit buffer, including
+.BR undo .
+For this purpose, the
+.BR global ,
+.BR v ,
+.BR open ,
+and
+.BR visual
+commands, and commands resulting from buffer executions and mapped
+character expansions, are considered single commands.
+.P
+If no action that can be undone preceded the
+.BR undo
+command, it shall be an error.
+.P
+If the
+.BR undo
+command restores lines that were marked, the mark shall also be
+restored unless it was reset subsequent to the deletion of the lines.
+.P
+.IR "Current line" :
+.IP " 1." 4
+If lines are added or changed in the file, set to the first line added
+or changed.
+.IP " 2." 4
+Set to the line before the first line deleted, if it exists.
+.IP " 3." 4
+Set to 1 if the edit buffer is not empty.
+.IP " 4." 4
+Set to zero.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Unmap"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+unm\fB[\fRap\fB][\fR!\fB] \fIlhs\fR
+.fi
+.P
+.RE
+.RE
+.P
+If
+.BR '!' 
+is appended to the command name, and if
+.IR lhs
+is not an entry in the list of text input mode map definitions, it
+shall be an error. Otherwise, delete
+.IR lhs
+from the list of text input mode map definitions.
+.P
+If no
+.BR '!' 
+is appended to the command name, and if
+.IR lhs
+is not an entry in the list of command mode map definitions, it shall
+be an error. Otherwise, delete
+.IR lhs
+from the list of command mode map definitions.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Version"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+ve\fB[\fRrsion\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Write a message containing version information for the editor. The
+format of the message is unspecified.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Visual"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fRvi\fB[\fRsual\fB][\fItype\fB][\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If
+.IR ex
+is currently in open or visual mode, the Synopsis and behavior of the
+visual command shall be the same as the
+.BR edit
+command, as specified by
+.IR "Edit".
+.P
+Otherwise, this command need not be supported on block-mode terminals
+or terminals with insufficient capabilities. If standard input,
+standard output, or standard error are not terminal devices, the
+results are unspecified.
+.P
+If
+.IR count
+is specified, the value of the
+.BR window
+edit option shall be set to
+.IR count
+(as described in
+.IR "window").
+If the
+.BR '\(ha' 
+type character was also specified, the
+.BR window
+edit option shall be set before being used by the type character.
+.P
+Enter visual mode. If
+.IR type
+is not specified, it shall be as if a
+.IR type
+of
+.BR '\(pl' 
+was specified. The
+.IR type
+shall cause the following effects:
+.IP "\fR+\fP" 6
+Place the beginning of the specified line at the top of the display.
+.IP "\fR-\fP" 6
+Place the end of the specified line at the bottom of the display.
+.IP "\fR.\fP" 6
+Place the beginning of the specified line in the middle of the display.
+.IP "\fR^\fP" 6
+If the specified line is less than or equal to the value of the
+.BR window
+edit option, set the line to 1; otherwise, decrement the line by the
+value of the
+.BR window
+edit option minus 1. Place the beginning of this line as close to the
+bottom of the displayed lines as possible, while still displaying the
+value of the
+.BR window
+edit option number of lines.
+.P
+.IR "Current line" :
+Set to the specified line.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Write"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRw\fB[\fRrite\fB][\fR!\fB][\fR>>\fB][\fIfile\fB]
+[\fI2addr\fB] \fRw\fB[\fRrite\fB][\fR!\fB][\fIfile\fB]
+[\fI2addr\fB] \fRwq\fB[\fR!\fB][\fR>>\fB][\fIfile\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If no lines are specified, the lines shall default to the entire file.
+.P
+The command
+.BR wq
+shall be equivalent to a
+.BR write
+command followed by a
+.BR quit
+command;
+.BR wq!
+shall be equivalent to
+.BR write!
+followed by
+.BR quit .
+In both cases, if the
+.BR write
+command fails, the
+.BR quit
+shall not be attempted.
+.P
+If the command name is not followed by one or more
+<blank>
+characters, or
+.IR file
+is not preceded by a
+.BR '!' 
+character, the
+.BR write
+shall be to a file.
+.IP " 1." 4
+If the
+.BR >>
+argument is specified, and the file already exists, the lines shall be
+appended to the file instead of replacing its contents. If the
+.BR >>
+argument is specified, and the file does not already exist, it is
+unspecified whether the write shall proceed as if the
+.BR >>
+argument had not been specified or if the write shall fail.
+.IP " 2." 4
+If the
+.BR readonly
+edit option is set (see
+.IR "readonly"),
+the
+.BR write
+shall fail.
+.IP " 3." 4
+If
+.IR file
+is specified, and is not the current pathname, and the file exists,
+the
+.BR write
+shall fail.
+.IP " 4." 4
+If
+.IR file
+is not specified, the current pathname shall be used. If there is no
+current pathname, the
+.BR write
+command shall fail.
+.IP " 5." 4
+If the current pathname is used, and the current pathname has been
+changed by the
+.BR file
+or
+.BR read
+commands, and the file exists, the
+.BR write
+shall fail. If the
+.BR write
+is successful, subsequent
+.BR write s
+shall not fail for this reason (unless the current pathname is changed
+again).
+.IP " 6." 4
+If the whole edit buffer is not being written, and the file to be
+written exists, the
+.BR write
+shall fail.
+.P
+For rules 1., 2., 3., and 5., the
+.BR write
+can be forced by appending the character
+.BR '!' 
+to the command name.
+.P
+For rules 2., 3., and 5., the
+.BR write
+can be forced by setting the
+.BR writeany
+edit option.
+.P
+Additional, implementation-defined tests may cause the
+.BR write
+to fail.
+.P
+If the edit buffer is empty, a file without any contents shall be written.
+.P
+An informational message shall be written noting the number of lines
+and bytes written.
+.P
+Otherwise, if the command is followed by one or more
+<blank>
+characters, and the file is preceded by
+.BR '!' ,
+the rest of the line after the
+.BR '!' 
+shall have
+.BR '%' ,
+.BR '#' ,
+and
+.BR '!' 
+characters expanded as described in
+.IR "Command Line Parsing in ex".
+.P
+The
+.IR ex
+utility shall then pass two arguments to the program named by the
+.BR shell
+edit option; the first shall be
+.BR \-c
+and the second shall be the expanded arguments to the
+.BR write
+command as a single argument. The specified lines shall be written to
+the standard input of the command. The standard error and standard
+output of the program, if any, shall be written as described for the
+.BR print
+command. If the last character in that output is not a
+<newline>,
+a
+<newline>
+shall be written at the end of the output.
+.P
+The special meaning of the
+.BR '!' 
+following the
+.BR write
+command can be overridden by escaping it with a
+<backslash>
+character.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Write and Exit"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRx\fB[\fRit\fB][\fR!\fB][\fIfile\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If the edit buffer has not been modified since the last complete
+.BR write ,
+.BR xit
+shall be equivalent to the
+.BR quit
+command, or if a
+.BR '!' 
+is appended to the command name, to
+.BR quit! .
+.P
+Otherwise,
+.BR xit
+shall be equivalent to the
+.BR wq
+command, or if a
+.BR '!' 
+is appended to the command name, to
+.BR wq! .
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Yank"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB] \fRya\fB[\fRnk\fB][\fIbuffer\fB][\fIcount\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Copy the specified lines to the specified buffer (by default, the
+unnamed buffer), which shall become a line-mode buffer.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Adjust Window"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fRz\fB[\fR!\fB][\fItype \fR...\fB][\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If no line is specified, the current line shall be the default; if
+.IR type
+is omitted as well, the current line value shall first be incremented
+by 1. If incrementing the current line would cause it to be greater
+than the last line in the edit buffer, it shall be an error.
+.P
+If there are
+<blank>
+characters between the
+.IR type
+argument and the preceding
+.BR z
+command name or optional
+.BR '!' 
+character, it shall be an error.
+.P
+If
+.IR count
+is specified, the value of the
+.BR window
+edit option shall be set to
+.IR count
+(as described in
+.IR "window").
+If
+.IR count
+is omitted, it shall default to 2 times the value of the
+.BR scroll
+edit option, or if
+.BR !
+was specified, the number of lines in the display minus 1.
+.P
+If
+.IR type
+is omitted, then
+.IR count
+lines starting with the specified line shall be written. Otherwise,
+.IR count
+lines starting with the line specified by the
+.IR type
+argument shall be written.
+.P
+The
+.IR type
+argument shall change the lines to be written. The possible values of
+.IR type
+are as follows:
+.IP "\fR\-\fP" 6
+The specified line shall be decremented by the following value:
+.RS 6 
+.sp
+.RS 4
+.nf
+
+(((number of \(aq-\(aq characters) x \fIcount\fR) -1)
+.fi
+.P
+.RE
+.P
+If the calculation would result in a number less than 1, it shall be an
+error. Write lines from the edit buffer, starting at the new value of
+line, until
+.IR count
+lines or the last line in the edit buffer has been written.
+.RE
+.IP "\fR+\fP" 6
+The specified line shall be incremented by the following value:
+.RS 6 
+.sp
+.RS 4
+.nf
+
+(((number of \(aq+\(aq characters) -1) x \fIcount\fR) +1
+.fi
+.P
+.RE
+.P
+If the calculation would result in a number greater than the last line
+in the edit buffer, it shall be an error. Write lines from the edit
+buffer, starting at the new value of line, until
+.IR count
+lines or the last line in the edit buffer has been written.
+.RE
+.IP "\fR=\fR,\fR.\fR" 6
+If more than a single
+.BR '.' 
+or
+.BR '=' 
+is specified, it shall be an error. The following steps shall be
+taken:
+.RS 6 
+.IP " 1." 4
+If
+.IR count
+is zero, nothing shall be written.
+.IP " 2." 4
+Write as many of the
+.IR N
+lines before the current line in the edit buffer as exist. If
+.IR count
+or
+.BR '!' 
+was specified,
+.IR N
+shall be:
+.RS 4 
+.sp
+.RS 4
+.nf
+
+(\fIcount\fR -1) /2
+.fi
+.P
+.RE
+.P
+Otherwise,
+.IR N
+shall be:
+.sp
+.RS 4
+.nf
+
+(\fIcount\fP -3) /2
+.fi
+.P
+.RE
+.P
+If
+.IR N
+is a number less than 3, no lines shall be written.
+.RE
+.IP " 3." 4
+If
+.BR '=' 
+was specified as the type character, write a line consisting of the
+smaller of the number of columns in the display divided by two, or 40
+.BR '\-' 
+characters.
+.IP " 4." 4
+Write the current line.
+.IP " 5." 4
+Repeat step 3.
+.IP " 6." 4
+Write as many of the
+.IR N
+lines after the current line in the edit buffer as exist.
+.IR N
+shall be defined as in step 2. If
+.IR N
+is a number less than 3, no lines shall be written. If
+.IR count
+is less than 3, no lines shall be written.
+.RE
+.IP "\fR^\fP" 6
+The specified line shall be decremented by the following value:
+.RS 6 
+.sp
+.RS 4
+.nf
+
+(((number of \(aq\(ha\(aq characters) +1) x \fIcount\fR) -1
+.fi
+.P
+.RE
+.P
+If the calculation would result in a number less than 1, it shall be an
+error. Write lines from the edit buffer, starting at the new value of
+line, until
+.IR count
+lines or the last line in the edit buffer has been written.
+.RE
+.P
+.IR "Current line" :
+Set to the last line written, unless the type is
+.BR = ,
+in which case, set to the specified line.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Escape"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+! \fIcommand
+\fB[\fIaddr\fB]\fR! \fIcommand\fR
+.fi
+.P
+.RE
+.RE
+.P
+The contents of the line after the
+.BR '!' 
+shall have
+.BR '%' ,
+.BR '#' ,
+and
+.BR '!' 
+characters expanded as described in
+.IR "Command Line Parsing in ex".
+If the expansion causes the text of the line to change, it shall be
+redisplayed, preceded by a single
+.BR '!' 
+character.
+.P
+The
+.IR ex
+utility shall execute the program named by the
+.BR shell
+edit option. It shall pass two arguments to the program; the first
+shall be
+.BR \-c ,
+and the second shall be the expanded arguments to the
+.BR !
+command as a single argument.
+.P
+If no lines are specified, the standard input, standard output, and
+standard error of the program shall be set to the standard input,
+standard output, and standard error of the
+.IR ex
+program when it was invoked. In addition, a warning message shall be
+written if the edit buffer has been modified since the last complete
+write, and the
+.BR warn
+edit option is set.
+.P
+If lines are specified, they shall be passed to the program as standard
+input, and the standard output and standard error of the program shall
+replace those lines in the edit buffer. Each line in the program output
+(as delimited by
+<newline>
+characters or the end of the output if it is not immediately preceded by a
+<newline>),
+shall be a separate line in the edit buffer. Any occurrences of
+<carriage-return>
+and
+<newline>
+pairs in the output shall be treated as single
+<newline>
+characters. The specified lines shall be copied into the unnamed buffer
+before they are replaced, and the unnamed buffer shall become a line-mode
+buffer.
+.P
+If in
+.IR ex
+mode, a single
+.BR '!' 
+character shall be written when the program completes.
+.P
+This command shall be affected by the
+.BR shell
+and
+.BR warn
+edit options. If no lines are specified, this command shall be affected
+by the
+.BR autowrite
+and
+.BR writeany
+edit options. If lines are specified, this command shall be affected by
+the
+.BR autoprint
+edit option.
+.br
+.P
+.IR "Current line" :
+.IP " 1." 4
+If no lines are specified, unchanged.
+.IP " 2." 4
+Otherwise, set to the last line read in, if any lines are read in.
+.IP " 3." 4
+Otherwise, set to the line before the first line of the lines
+specified, if that line exists.
+.IP " 4." 4
+Otherwise, set to the first line of the edit buffer if the edit buffer
+is not empty.
+.IP " 5." 4
+Otherwise, set to zero.
+.P
+.IR "Current column" :
+If no lines are specified, unchanged. Otherwise, set to non-\c
+<blank>.
+.SS "Shift Left"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB]\fR <\fB[\fR< ...\fB][\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Shift the specified lines to the start of the line; the number of
+column positions to be shifted shall be the number of command
+characters times the value of the
+.BR shiftwidth
+edit option. Only leading
+<blank>
+characters shall be deleted or changed into other
+<blank>
+characters in shifting; other characters shall not be affected.
+.P
+Lines to be shifted shall be copied into the unnamed buffer, which
+shall become a line-mode buffer.
+.P
+This command shall be affected by the
+.BR autoprint
+edit option.
+.P
+.IR "Current line" :
+Set to the last line in the lines specified.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Shift Right"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB]\fR >\fB[\fR> ...\fB][\fIcount\fB][\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+Shift the specified lines away from the start of the line; the number
+of column positions to be shifted shall be the number of command
+characters times the value of the
+.BR shiftwidth
+edit option. The shift shall be accomplished by adding
+<blank>
+characters as a prefix to the line or changing leading
+<blank>
+characters into other
+<blank>
+characters. Empty lines shall not be changed.
+.P
+Lines to be shifted shall be copied into the unnamed buffer, which
+shall become a line-mode buffer.
+.P
+This command shall be affected by the
+.BR autoprint
+edit option.
+.P
+.IR "Current line" :
+Set to the last line in the lines specified.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "<control>\(hyD"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+<control>-D
+.fi
+.P
+.RE
+.RE
+.P
+Write the next
+.IR n
+lines, where
+.IR n
+is the minimum of the values of the
+.BR scroll
+edit option and the number of lines after the current line in the edit
+buffer. If the current line is the last line of the edit buffer it
+shall be an error.
+.P
+.IR "Current line" :
+Set to the last line written.
+.P
+.IR "Current column" :
+Set to non-\c
+<blank>.
+.SS "Write Line Number"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI1addr\fB] \fR= \fB[\fIflags\fB]\fR
+.fi
+.P
+.RE
+.RE
+.P
+If
+.IR line
+is not specified, it shall default to the last line in the edit buffer.
+Write the line number of the specified line.
+.P
+.IR "Current line" :
+Unchanged.
+.P
+.IR "Current column" :
+Unchanged.
+.SS "Execute"
+.IP "\fISynopsis\fR:" 10
+.sp -1v
+.RS 10 
+.sp
+.RS 4
+.nf
+
+\fB[\fI2addr\fB]\fR @ \fIbuffer\fR
+\fB[\fI2addr\fB]\fR * \fIbuffer\fR
+.fi
+.P
+.RE
+.RE
+.P
+If no buffer is specified or is specified as
+.BR '@' 
+or
+.BR '*' ,
+the last buffer executed shall be used. If no previous buffer has been
+executed, it shall be an error.
+.P
+For each line specified by the addresses, set the current line (\c
+.BR '.' )
+to the specified line, and execute the contents of the named
+.IR buffer
+(as they were at the time the
+.BR @
+command was executed) as
+.IR ex
+commands. For each line of a line-mode buffer, and all but the last
+line of a character-mode buffer, the
+.IR ex
+command parser shall behave as if the line was terminated by a
+<newline>.
+.P
+If an error occurs during this process, or a line specified by the
+addresses does not exist when the current line would be set to it, or
+more than a single line was specified by the addresses, and the
+contents of the edit buffer are replaced (for example, by the
+.IR ex
+.BR :edit
+command) an error message shall be written, and no more commands
+resulting from the execution of this command shall be processed.
+.P
+.IR "Current line" :
+As specified for the individual
+.IR ex
+commands.
+.P
+.IR "Current column" :
+As specified for the individual
+.IR ex
+commands.
+.SS "Regular Expressions in ex"
+.P
+The
+.IR ex
+utility shall support regular expressions that are a superset of the
+basic regular expressions described in the Base Definitions volume of POSIX.1\(hy2017,
+.IR "Section 9.3" ", " "Basic Regular Expressions".
+A null regular expression (\c
+.BR \(dq//\(dq )
+shall be equivalent to the last regular expression encountered.
+.P
+Regular expressions can be used in addresses to specify lines and, in
+some commands (for example, the
+.BR substitute
+command), to specify portions of a line to be substituted.
+.P
+The following constructs can be used to enhance the basic regular
+expressions:
+.IP "\fR\e<\fR" 6
+Match the beginning of a
+.IR word .
+(See the definition of
+.IR word
+at the beginning of
+.IR "Command Descriptions in ex".)
+.IP "\fR\e>\fR" 6
+Match the end of a
+.IR word .
+.IP "\fR~\fR" 6
+Match the replacement part of the last
+.BR substitute
+command. The
+<tilde>
+(\c
+.BR '\(ti' )
+character can be escaped in a regular expression to become a normal
+character with no special meaning. The
+<backslash>
+shall be discarded.
+.P
+When the editor option
+.BR magic
+is not set, the only characters with special meanings shall be
+.BR '\(ha' 
+at the beginning of a pattern,
+.BR '$' 
+at the end of a pattern, and
+<backslash>.
+The characters
+.BR '.' ,
+.BR '*' ,
+.BR '[' ,
+and
+.BR '\(ti' 
+shall be treated as ordinary characters unless preceded by a
+<backslash>;
+when preceded by a
+<backslash>
+they shall regain their special meaning, or in the case of
+<backslash>,
+be handled as a single
+<backslash>.
+<backslash>
+characters used to escape other characters shall be discarded.
+.SS "Replacement Strings in ex"
+.P
+The character
+.BR '&' 
+(\c
+.BR '\e&' 
+if the editor option
+.BR magic
+is not set) in the replacement string shall stand for the text matched
+by the pattern to be replaced. The character
+.BR '\(ti' 
+(\c
+.BR '\e\(ti' 
+if
+.BR magic
+is not set) shall be replaced by the replacement part of the previous
+.BR substitute
+command. The sequence
+.BR '\en' ,
+where
+.IR n
+is an integer, shall be replaced by the text matched by the
+corresponding back-reference expression. If the corresponding
+back-reference expression does not match, then the characters
+.BR '\en' 
+shall be replaced by the empty string.
+.P
+The strings
+.BR '\el' ,
+.BR '\eu' ,
+.BR '\eL' ,
+and
+.BR '\eU' 
+can be used to modify the case of elements in the replacement string
+(using the
+.BR '\e&' 
+or
+.BR \(dq\e\(dq digit)
+notation. The string
+.BR '\el' 
+(\c
+.BR '\eu' )
+shall cause the character that follows to be converted to lowercase
+(uppercase). The string
+.BR '\eL' 
+(\c
+.BR '\eU' )
+shall cause all characters subsequent to it to be converted to
+lowercase (uppercase) as they are inserted by the substitution until
+the string
+.BR '\ee' 
+or
+.BR '\eE' ,
+or the end of the replacement string, is encountered.
+.P
+Otherwise, any character following a
+<backslash>
+shall be treated as that literal character, and the escaping
+<backslash>
+shall be discarded.
+.P
+An example of case conversion with the
+.BR s
+command is as follows:
+.sp
+.RS 4
+.nf
+
+\fB:\fRp
+\fBThe cat sat on the mat.
+\fB:\fRs/\e<.at\e>/\eu&/gp
+\fBThe Cat Sat on the Mat.
+\fB:\fRs/S\e(.*\e)M/S\eU\e1\eeM/p
+\fBThe Cat SAT ON THE Mat.\fR
+.fi
+.P
+.RE
+.SS "Edit Options in ex"
+.P
+The
+.IR ex
+utility has a number of options that modify its behavior. These options
+have default settings, which can be changed using the
+.BR set
+command.
+.P
+Options are Boolean unless otherwise specified.
+.SS "autoindent, ai"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR autoindent
+is set, each line in input mode shall be indented (using first as many
+<tab>
+characters as possible, as determined by the editor option
+.BR tabstop ,
+and then using
+<space>
+characters) to align with another line, as follows:
+.IP " 1." 4
+If in open or visual mode and the text input is part of a line-oriented
+command (see the EXTENDED DESCRIPTION in
+.IR "\fIvi\fR\^"),
+align to the first column.
+.IP " 2." 4
+Otherwise, if in open or visual mode, indentation for each line shall
+be set as follows:
+.RS 4 
+.IP " a." 4
+If a line was previously inserted as part of this command, it shall be
+set to the indentation of the last inserted line by default, or as
+otherwise specified for the
+<control>\(hyD
+character in
+.IR "Input Mode Commands in vi".
+.IP " b." 4
+Otherwise, it shall be set to the indentation of the previous current
+line, if any; otherwise, to the first column.
+.RE
+.IP " 3." 4
+For the
+.IR ex
+.BR a ,
+.BR i ,
+and
+.BR c
+commands, indentation for each line shall be set as follows:
+.RS 4 
+.IP " a." 4
+If a line was previously inserted as part of this command, it shall be
+set to the indentation of the last inserted line by default, or as
+otherwise specified for the
+.IR eof
+character in
+.IR "Scroll".
+.IP " b." 4
+Otherwise, if the command is the
+.IR ex
+.BR a
+command, it shall be set to the line appended after, if any; otherwise
+to the first column.
+.IP " c." 4
+Otherwise, if the command is the
+.IR ex
+.BR i
+command, it shall be set to the line inserted before, if any; otherwise
+to the first column.
+.IP " d." 4
+Otherwise, if the command is the
+.IR ex
+.BR c
+command, it shall be set to the indentation of the line replaced.
+.RE
+.SS "autoprint, ap"
+.P
+[Default \fIset\fR]
+.P
+If
+.BR autoprint
+is set, the current line shall be written after each
+.IR ex
+command that modifies the contents of the current edit buffer, and
+after each
+.BR tag
+command for which the tag search pattern was found or tag line number
+was valid, unless:
+.IP " 1." 4
+The command was executed while in open or visual mode.
+.IP " 2." 4
+The command was executed as part of a
+.BR global
+or
+.BR v
+command or
+.BR @
+buffer execution.
+.IP " 3." 4
+The command was the form of the
+.BR read
+command that reads a file into the edit buffer.
+.IP " 4." 4
+The command was the
+.BR append ,
+.BR change ,
+or
+.BR insert
+command.
+.IP " 5." 4
+The command was not terminated by a
+<newline>.
+.IP " 6." 4
+The current line shall be written by a flag specified to the command;
+for example,
+.BR "delete #"
+shall write the current line as specified for the flag modifier to the
+.BR delete
+command, and not as specified by the
+.BR autoprint
+edit option.
+.SS "autowrite, aw"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR autowrite
+is set, and the edit buffer has been modified since it was last
+completely written to any file, the contents of the edit buffer shall
+be written as if the
+.IR ex
+.BR write
+command had been specified without arguments, before each command
+affected by the
+.BR autowrite
+edit option is executed. Appending the character
+.BR '!' 
+to the command name of any of the
+.IR ex
+commands except
+.BR '!' 
+shall prevent the write. If the write fails, it shall be an error and
+the command shall not be executed.
+.SS "beautify, bf"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR beautify
+is set, all non-printable characters, other than
+<tab>,
+<newline>,
+and
+<form-feed>
+characters, shall be discarded from text read in from files.
+.SS "directory, dir"
+.P
+[Default \fIimplementation-defined\fR]
+.P
+The value of this option specifies the directory in which the editor
+buffer is to be placed. If this directory is not writable by the user,
+the editor shall quit.
+.SS "edcompatible, ed"
+.P
+[Default \fIunset\fR]
+.P
+Causes the presence of
+.BR g
+and
+.BR c
+suffixes on substitute commands to be remembered, and toggled by
+repeating the suffixes.
+.SS "errorbells, eb"
+.P
+[Default \fIunset\fR]
+.P
+If the editor is in
+.IR ex
+mode, and the terminal does not support a standout mode (such as
+inverse video), and
+.BR errorbells
+is set, error messages shall be preceded by alerting the terminal.
+.SS "exrc"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR exrc
+is set,
+.IR ex
+shall access any
+.BR .exrc
+file in the current directory, as described in
+.IR "Initialization in ex and vi".
+If
+.BR exrc
+is not set,
+.IR ex
+shall ignore any
+.BR .exrc
+file in the current directory during initialization, unless the current
+directory is that named by the
+.IR HOME
+environment variable.
+.SS "ignorecase, ic"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR ignorecase
+is set, characters that have uppercase and lowercase representations
+shall have those representations considered as equivalent for purposes
+of regular expression comparison.
+.P
+The
+.BR ignorecase
+edit option shall affect all remembered regular expressions; for
+example, unsetting the
+.BR ignorecase
+edit option shall cause a subsequent
+.IR vi
+.BR n
+command to search for the last basic regular expression in a
+case-sensitive fashion.
+.SS "list"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR list
+is set, edit buffer lines written while in
+.IR ex
+command mode shall be written as specified for the
+.BR print
+command with the
+.BR l
+flag specified. In open or visual mode, each edit buffer line shall be
+displayed as specified for the
+.IR ex
+.BR print
+command with the
+.BR l
+flag specified. In open or visual text input mode, when the cursor
+does not rest on any character in the line, it shall rest on the
+.BR '$' 
+marking the end of the line.
+.SS "magic"
+.P
+[Default \fIset\fR]
+.P
+If
+.BR magic
+is set, modify the interpretation of characters in regular expressions
+and substitution replacement strings (see
+.IR "Regular Expressions in ex"
+and
+.IR "Replacement Strings in ex").
+.SS "mesg"
+.P
+[Default \fIset\fR]
+.P
+If
+.BR mesg
+is set, the permission for others to use the
+.BR write
+or
+.BR talk
+commands to write to the terminal shall be turned on while in open or
+visual mode. The shell-level command
+.IR mesg
+.BR n
+shall take precedence over any setting of the
+.IR ex
+.BR mesg
+option; that is, if
+.BR "mesg y"
+was issued before the editor started (or in a shell escape), such as:
+.sp
+.RS 4
+.nf
+
+:!mesg y
+.fi
+.P
+.RE
+.P
+the
+.BR mesg
+option in
+.IR ex
+shall suppress incoming messages, but the
+.BR mesg
+option shall not enable incoming messages if
+.BR "mesg n"
+was issued.
+.SS "number, nu"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR number
+is set, edit buffer lines written while in
+.IR ex
+command mode shall be written with line numbers, in the format
+specified by the
+.BR print
+command with the
+.BR #
+flag specified. In
+.IR ex
+text input mode, each line shall be preceded by the line number it will
+have in the file.
+.P
+In open or visual mode, each edit buffer line shall be displayed with a
+preceding line number, in the format specified by the
+.IR ex
+.BR print
+command with the
+.BR #
+flag specified. This line number shall not be considered part of the
+line for the purposes of evaluating the current column; that is, column
+position 1 shall be the first column position after the format
+specified by the
+.BR print
+command.
+.SS "paragraphs, para"
+.P
+[Default in the POSIX locale \fRIPLPPPQPP LIpplpipbp\fR]
+.P
+The
+.BR paragraphs
+edit option shall define additional paragraph boundaries for the open
+and visual mode commands. The
+.BR paragraphs
+edit option can be set to a character string consisting of zero or more
+character pairs. It shall be an error to set it to an odd number of
+characters.
+.SS "prompt"
+.P
+[Default \fIset\fR]
+.P
+If
+.BR prompt
+is set,
+.IR ex
+command mode input shall be prompted for with a
+<colon>
+(\c
+.BR ':' );
+when unset, no prompt shall be written.
+.SS "readonly"
+.P
+[Default \fIsee text\fR]
+.P
+If the
+.BR readonly
+edit option is set, read-only mode shall be enabled (see
+.IR "Write").
+The
+.BR readonly
+edit option shall be initialized to set if either of the following
+conditions are true:
+.IP " *" 4
+The command-line option
+\-R
+was specified.
+.IP " *" 4
+Performing actions equivalent to the
+\fIaccess\fR()
+function called with the following arguments indicates that the file
+lacks write permission:
+.RS 4 
+.IP " 1." 4
+The current pathname is used as the
+.IR path
+argument.
+.IP " 2." 4
+The constant
+.BR W_OK
+is used as the
+.IR amode
+argument.
+.RE
+.P
+The
+.BR readonly
+edit option may be initialized to set for other,
+implementation-defined reasons. The
+.BR readonly
+edit option shall not be initialized to unset based on any special
+privileges of the user or process. The
+.BR readonly
+edit option shall be reinitialized each time that the contents of the
+edit buffer are replaced (for example, by an
+.BR edit
+or
+.BR next
+command) unless the user has explicitly set it, in which case it shall
+remain set until the user explicitly unsets it. Once unset, it shall
+again be reinitialized each time that the contents of the edit buffer
+are replaced.
+.SS "redraw"
+.P
+[Default \fIunset\fR]
+.P
+The editor simulates an intelligent terminal on a dumb terminal.
+(Since this is likely to require a large amount of output to the
+terminal, it is useful only at high transmission speeds.)
+.SS "remap"
+.P
+[Default \fIset\fR]
+.P
+If
+.BR remap
+is set, map translation shall allow for maps defined in terms of other
+maps; translation shall continue until a final product is obtained. If
+unset, only a one-step translation shall be done.
+.SS "report"
+.P
+[Default 5]
+.P
+The value of this
+.BR report
+edit option specifies what number of lines being added, copied,
+deleted, or modified in the edit buffer will cause an informational
+message to be written to the user. The following conditions shall cause
+an informational message. The message shall contain the number of lines
+added, copied, deleted, or modified, but is otherwise unspecified.
+.IP " *" 4
+An
+.IR ex
+or
+.IR vi
+editor command, other than
+.BR open ,
+.BR undo ,
+or
+.BR visual ,
+that modifies at least the value of the
+.BR report
+edit option number of lines, and which is not part of an
+.IR ex
+.BR global
+or
+.BR v
+command, or
+.IR ex
+or
+.IR vi
+buffer execution, shall cause an informational message to be written.
+.IP " *" 4
+An
+.IR ex
+.BR yank
+or
+.IR vi
+.BR y
+or
+.BR Y
+command, that copies at least the value of the
+.BR report
+edit option plus 1 number of lines, and which is not part of an
+.IR ex
+.BR global
+or
+.BR v
+command, or
+.IR ex
+or
+.IR vi
+buffer execution, shall cause an informational message to be written.
+.IP " *" 4
+An
+.IR ex
+.BR global ,
+.BR v ,
+.BR open ,
+.BR undo ,
+or
+.BR visual
+command or
+.IR ex
+or
+.IR vi
+buffer execution, that adds or deletes a total of at least the value of
+the
+.BR report
+edit option number of lines, and which is not part of an
+.IR ex
+.BR global
+or
+.BR v
+command, or
+.IR ex
+or
+.IR vi
+buffer execution, shall cause an informational message to be written.
+(For example, if 3 lines were added and 8 lines deleted during an
+.IR ex
+.BR visual
+command, 5 would be the number compared against the
+.BR report
+edit option after the command completed.)
+.SS "scroll, scr"
+.P
+[Default (number of lines in the display \-1)/2]
+.P
+The value of the
+.BR scroll
+edit option shall determine the number of lines scrolled by the
+.IR ex
+<control>\(hyD
+and
+.BR z
+commands. For the
+.IR vi
+<control>\(hyD
+and
+<control>\(hyU
+commands, it shall be the initial number of lines to scroll when no
+previous
+<control>\(hyD
+or
+<control>\(hyU
+command has been executed.
+.SS "sections"
+.P
+[Default in the POSIX locale \fRNHSHH HUnhsh\fR]
+.P
+The
+.BR sections
+edit option shall define additional section boundaries for the open and
+visual mode commands. The
+.BR sections
+edit option can be set to a character string consisting of zero or more
+character pairs; it shall be an error to set it to an odd number of
+characters.
+.SS "shell, sh"
+.P
+[Default from the environment variable
+.IR SHELL ]
+.P
+The value of this option shall be a string. The default shall be taken
+from the
+.IR SHELL
+environment variable. If the
+.IR SHELL
+environment variable is null or empty, the
+.IR sh
+(see
+.IR "\fIsh\fR\^")
+utility shall be the default.
+.SS "shiftwidth, sw"
+.P
+[Default 8]
+.P
+The value of this option shall give the width in columns of an
+indentation level used during autoindentation and by the shift commands
+(\c
+.BR <
+and
+.BR > ).
+.SS "showmatch, sm"
+.P
+[Default \fIunset\fR]
+.P
+The functionality described for the
+.BR showmatch
+edit option need not be supported on block-mode terminals or terminals
+with insufficient capabilities.
+.P
+If
+.BR showmatch
+is set, in open or visual mode, when a
+.BR ')' 
+or
+.BR '}' 
+is typed, if the matching
+.BR '(' 
+or
+.BR '{' 
+is currently visible on the display, the matching
+.BR '(' 
+or
+.BR '{' 
+shall be flagged moving the cursor to its location for an unspecified
+amount of time.
+.SS "showmode"
+.P
+[Default \fIunset\fP]
+.P
+If
+.BR showmode
+is set, in open or visual mode, the current mode that the editor is in
+shall be displayed on the last line of the display. Command mode and
+text input mode shall be differentiated; other unspecified modes and
+implementation-defined information may be displayed.
+.SS "slowopen"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR slowopen
+is set during open and visual text input modes, the editor shall not
+update portions of the display other than those display line columns
+that display the characters entered by the user (see
+.IR "Input Mode Commands in vi").
+.SS "tabstop, ts"
+.P
+[Default 8]
+.P
+The value of this edit option shall specify the column boundary used by
+a
+<tab>
+in the display (see
+.IR "autoprint" ", " "ap"
+and
+.IR "Input Mode Commands in vi").
+.SS "taglength, tl"
+.P
+[Default zero]
+.P
+The value of this edit option shall specify the maximum number of
+characters that are considered significant in the user-specified tag
+name and in the tag name from the tags file. If the value is zero, all
+characters in both tag names shall be significant.
+.SS "tags"
+.P
+[Default \fIsee text\fP]
+.P
+The value of this edit option shall be a string of
+<blank>-delimited
+pathnames of files used by the
+.BR tag
+command. The default value is unspecified.
+.SS "term"
+.P
+[Default from the environment variable
+.IR TERM ]
+.P
+The value of this edit option shall be a string. The default shall be
+taken from the
+.IR TERM
+variable in the environment. If the
+.IR TERM
+environment variable is empty or null, the default is unspecified. The
+editor shall use the value of this edit option to determine the type of
+the display device.
+.P
+The results are unspecified if the user changes the value of the term
+edit option after editor initialization.
+.SS "terse"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR terse
+is set, error messages may be less verbose. However, except for this
+caveat, error messages are unspecified. Furthermore, not all error
+messages need change for different settings of this option.
+.SS "warn"
+.P
+[Default \fIset\fR]
+.P
+If
+.BR warn
+is set, and the contents of the edit buffer have been modified since
+they were last completely written, the editor shall write a warning
+message before certain
+.BR !
+commands (see
+.IR "Escape").
+.SS "window"
+.P
+[Default \fIsee text\fR]
+.P
+A value used in open and visual mode, by the
+<control>\(hyB
+and
+<control>\(hyF
+commands, and, in visual mode, to specify the number of lines displayed
+when the screen is repainted.
+.P
+If the
+.BR \-w
+command-line option is not specified, the default value shall be set to
+the value of the
+.IR LINES
+environment variable. If the
+.IR LINES
+environment variable is empty or null, the default shall be the number
+of lines in the display minus 1.
+.P
+Setting the
+.BR window
+edit option to zero or to a value greater than the number of lines in
+the display minus 1 (either explicitly or based on the
+.BR \-w
+option or the
+.IR LINES
+environment variable) shall cause the
+.BR window
+edit option to be set to the number of lines in the display minus 1.
+.P
+The baud rate of the terminal line may change the default in an
+implementation-defined manner.
+.SS "wrapmargin, wm"
+.P
+[Default 0]
+.P
+If the value of this edit option is zero, it shall have no effect.
+.P
+If not in the POSIX locale, the effect of this edit option is
+implementation-defined.
+.P
+Otherwise, it shall specify a number of columns from the ending margin
+of the terminal.
+.P
+During open and visual text input modes, for each character for which
+any part of the character is displayed in a column that is less than
+.BR wrapmargin
+columns from the ending margin of the display line, the editor shall
+behave as follows:
+.IP " 1." 4
+If the character triggering this event is a
+<blank>,
+it, and all immediately preceding
+<blank>
+characters on the current line entered during the execution of the
+current text input command, shall be discarded, and the editor shall
+behave as if the user had entered a single
+<newline>
+instead. In addition, if the next user-entered character is a
+<space>,
+it shall be discarded as well.
+.IP " 2." 4
+Otherwise, if there are one or more
+<blank>
+characters on the current line immediately preceding the last group of
+inserted non-\c
+<blank>
+characters which was entered during the execution of the current text
+input command, the
+<blank>
+characters shall be replaced as if the user had entered a single
+<newline>
+instead.
+.P
+If the
+.BR autoindent
+edit option is set, and the events described in 1. or 2. are performed,
+any
+<blank>
+characters at or after the cursor in the current line shall be discarded.
+.P
+The ending margin shall be determined by the system or overridden by
+the user, as described for
+.IR COLUMNS
+in the ENVIRONMENT VARIABLES section and the Base Definitions volume of POSIX.1\(hy2017,
+.IR "Chapter 8" ", " "Environment Variables".
+.SS "wrapscan, ws"
+.P
+[Default \fIset\fR]
+.P
+If
+.BR wrapscan
+is set, searches (the
+.IR ex
+.BR /
+or
+.BR ?
+addresses, or open and visual mode
+.BR / ,
+.BR ? ,
+.BR N ,
+and
+.BR n
+commands) shall wrap around the beginning or end of the edit buffer;
+when unset, searches shall stop at the beginning or end of the edit
+buffer.
+.SS "writeany, wa"
+.P
+[Default \fIunset\fR]
+.P
+If
+.BR writeany
+is set, some of the checks performed when executing the
+.IR ex
+.BR write
+commands shall be inhibited, as described in editor option
+.BR autowrite .
+.SH "EXIT STATUS"
+The following exit values shall be returned:
+.IP "\00" 6
+Successful completion.
+.IP >0 6
+An error occurred.
+.SH "CONSEQUENCES OF ERRORS"
+When any error is encountered and the standard input is not a terminal
+device file,
+.IR ex
+shall not write the file or return to command or text input mode, and
+shall terminate with a non-zero exit status.
+.P
+Otherwise, when an unrecoverable error is encountered, it shall be
+equivalent to a SIGHUP asynchronous event.
+.P
+Otherwise, when an error is encountered, the editor shall behave as
+specified in
+.IR "Command Line Parsing in ex".
+.LP
+.IR "The following sections are informative."
+.SH "APPLICATION USAGE"
+If a SIGSEGV signal is received while
+.IR ex
+is saving a file, the file might not be successfully saved.
+.P
+The
+.BR next
+command can accept more than one file, so usage such as:
+.sp
+.RS 4
+.nf
+
+next `ls [abc]*`
+.fi
+.P
+.RE
+.P
+is valid; it would not be valid for the
+.BR edit
+or
+.BR read
+commands, for example, because they expect only one file and
+unspecified results occur.
+.SH EXAMPLES
+None.
+.SH RATIONALE
+The
+.IR ex /\c
+.IR vi
+specification is based on the historical practice found in the 4 BSD and
+System V implementations of
+.IR ex
+and
+.IR vi .
+.P
+A
+.IR "restricted editor"
+(both the historical
+.IR red
+utility and modifications to
+.IR ex )
+were considered and rejected for inclusion. Neither option provided the
+level of security that users might expect.
+.P
+It is recognized that
+.IR ex
+visual mode and related features would be difficult, if not impossible,
+to implement satisfactorily on a block-mode terminal, or a terminal
+without any form of cursor addressing; thus, it is not a mandatory
+requirement that such features should work on all terminals. It is the
+intention, however, that an
+.IR ex
+implementation should provide the full set of capabilities on all
+terminals capable of supporting them.
+.SS "Options"
+.P
+The
+.BR \-c
+replacement for
+.BR + \c
+.IR command
+was inspired by the
+.BR \-e
+option of
+.IR sed .
+Historically, all such commands (see
+.BR edit
+and
+.BR next
+as well) were executed from the last line of the edit buffer. This
+meant, for example, that
+.BR \(dq+/pattern\(dq 
+would fail unless the
+.BR wrapscan
+option was set. POSIX.1\(hy2008 requires conformance to historical practice. The
+.BR \(pl \c
+.IR command
+option is no longer specified by POSIX.1\(hy2008 but may be present in
+some implementations. Historically, some implementations restricted the
+.IR ex
+commands that could be listed as part of the command line arguments.
+For consistency, POSIX.1\(hy2008 does not permit these restrictions.
+.P
+In historical implementations of the editor, the
+.BR \-R
+option (and the
+.BR readonly
+edit option) only prevented overwriting of files; appending to files
+was still permitted, mapping loosely into the
+.IR csh
+.BR noclobber
+variable. Some implementations, however, have not followed this
+semantic, and
+.BR readonly
+does not permit appending either. POSIX.1\(hy2008 follows the latter practice,
+believing that it is a more obvious and intuitive meaning of
+.BR readonly .
+.P
+The
+.BR \-s
+option suppresses all interactive user feedback and is useful for
+editing scripts in batch jobs. The list of specific effects is
+historical practice. The terminal type ``incapable of supporting open
+and visual modes'' has historically been named ``dumb''.
+.P
+The
+.BR \-t
+option was required because the
+.IR ctags
+utility appears in POSIX.1\(hy2008 and the option is available in all historical
+implementations of
+.IR ex .
+.P
+Historically, the
+.IR ex
+and
+.IR vi
+utilities accepted a
+.BR \-x
+option, which did encryption based on the algorithm found in the
+historical
+.IR crypt
+utility. The
+.BR \-x
+option for encryption, and the associated
+.IR crypt
+utility, were omitted because the algorithm used was not specifiable
+and the export control laws of some nations make it difficult to export
+cryptographic technology. In addition, it did not historically provide
+the level of security that users might expect.
+.SS "Standard Input"
+.P
+An end-of-file condition is not equivalent to an end-of-file character.
+A common end-of-file character,
+<control>\(hyD,
+is historically an
+.IR ex
+command.
+.P
+There was no maximum line length in historical implementations of
+.IR ex .
+Specifically, as it was parsed in chunks, the addresses had a different
+maximum length than the filenames. Further, the maximum line buffer
+size was declared as BUFSIZ, which was different lengths on different
+systems. This version selected the value of
+{LINE_MAX}
+to impose a reasonable restriction on portable usage of
+.IR ex
+and to aid test suite writers in their development of realistic tests
+that exercise this limit.
+.SS "Input Files"
+.P
+It was an explicit decision by the standard developers that a
+<newline>
+be added to any file lacking one. It was believed that this feature of
+.IR ex
+and
+.IR vi
+was relied on by users in order to make text files lacking a trailing
+<newline>
+more portable. It is recognized that this will require a user-specified
+option or extension for implementations that permit
+.IR ex
+and
+.IR vi
+to edit files of type other than text if such files are not otherwise
+identified by the system. It was agreed that the ability to edit files
+of arbitrary type can be useful, but it was not considered necessary to
+mandate that an
+.IR ex
+or
+.IR vi
+implementation be required to handle files other than text files.
+.P
+The paragraph in the INPUT FILES section, ``By default, .\|.\|.'', is
+intended to close a long-standing security problem in
+.IR ex
+and
+.IR vi ;
+that of the ``modeline'' or ``modelines'' edit option. This feature
+allows any line in the first or last five lines of the file containing
+the strings
+.BR \(dqex:\(dq 
+or
+.BR \(dqvi:\(dq 
+(and, apparently,
+.BR \(dqei:\(dq 
+or
+.BR \(dqvx:\(dq )
+to be a line containing editor commands, and
+.IR ex
+interprets all the text up to the next
+.BR ':' 
+or
+<newline>
+as a command. Consider the consequences, for example, of an
+unsuspecting user using
+.IR ex
+or
+.IR vi
+as the editor when replying to a mail message in which a line such as:
+.sp
+.RS 4
+.nf
+
+ex:! rm -rf :
+.fi
+.P
+.RE
+.P
+appeared in the signature lines. The standard developers believed
+strongly that an editor should not by default interpret any lines of a
+file. Vendors are strongly urged to delete this feature from their
+implementations of
+.IR ex
+and
+.IR vi .
+.SS "Asynchronous Events"
+.P
+The intention of the phrase ``complete write'' is that the entire edit
+buffer be written to stable storage. The note regarding temporary files
+is intended for implementations that use temporary files to back edit
+buffers unnamed by the user.
+.P
+Historically, SIGQUIT was ignored by
+.IR ex ,
+but was the equivalent of the
+.BR Q
+command in visual mode; that is, it exited visual mode and entered
+.IR ex
+mode. POSIX.1\(hy2008 permits, but does not require, this behavior. Historically,
+SIGINT was often used by
+.IR vi
+users to terminate text input mode (\c
+<control>\(hyC
+is often easier to enter than
+<ESC>).
+Some implementations of
+.IR vi
+alerted the terminal on this event, and some did not. POSIX.1\(hy2008 requires
+that SIGINT behave identically to
+<ESC>,
+and that the terminal not be alerted.
+.P
+Historically, suspending the
+.IR ex
+editor during text input mode was similar to SIGINT, as completed lines
+were retained, but any partial line discarded, and the editor returned
+to command mode. POSIX.1\(hy2008 is silent on this issue; implementations are
+encouraged to follow historical practice, where possible.
+.P
+Historically, the
+.IR vi
+editor did not treat SIGTSTP as an asynchronous event, and it was
+therefore impossible to suspend the editor in visual text input mode.
+There are two major reasons for this. The first is that SIGTSTP is a
+broadcast signal on UNIX systems, and the chain of events where the
+shell
+.IR exec s
+an application that then
+.IR exec s
+.IR vi
+usually caused confusion for the terminal state if SIGTSTP was delivered
+to the process group in the default manner. The second was that most
+implementations of the UNIX
+.IR curses
+package did not handle SIGTSTP safely, and the receipt of SIGTSTP at
+the wrong time would cause them to crash. POSIX.1\(hy2008 is silent on this issue;
+implementations are encouraged to treat suspension as an asynchronous
+event if possible.
+.P
+Historically, modifications to the edit buffer made before SIGINT
+interrupted an operation were retained; that is, anywhere from zero to
+all of the lines to be modified might have been modified by the time
+the SIGINT arrived. These changes were not discarded by the arrival of
+SIGINT. POSIX.1\(hy2008 permits this behavior, noting that the
+.BR undo
+command is required to be able to undo these partially completed
+commands.
+.P
+The action taken for signals other than SIGINT, SIGCONT, SIGHUP, and
+SIGTERM is unspecified because some implementations attempt to save the
+edit buffer in a useful state when other signals are received.
+.SS "Standard Error"
+.P
+For
+.IR ex /\c
+.IR vi ,
+diagnostic messages are those messages reported as a result of a failed
+attempt to invoke
+.IR ex
+or
+.IR vi ,
+such as invalid options or insufficient resources, or an abnormal
+termination condition. Diagnostic messages should not be confused with
+the error messages generated by inappropriate or illegal user
+commands.
+.SS "Initialization in ex and vi"
+.P
+If an
+.IR ex
+command (other than
+.BR cd ,
+.BR chdir ,
+or
+.BR source )
+has a filename argument, one or both of the alternate and current
+pathnames will be set. Informally, they are set as follows:
+.IP " 1." 4
+If the
+.IR ex
+command is one that replaces the contents of the edit buffer, and it
+succeeds, the current pathname will be set to the filename argument
+(the first filename argument in the case of the
+.BR next
+command) and the alternate pathname will be set to the previous
+current pathname, if there was one.
+.IP " 2." 4
+In the case of the file read/write forms of the
+.BR read
+and
+.BR write
+commands, if there is no current pathname, the current pathname will
+be set to the filename argument.
+.IP " 3." 4
+Otherwise, the alternate pathname will be set to the filename
+argument.
+.P
+For example,
+.BR ":edit foo"
+and
+.BR ":recover foo" ,
+when successful, set the current pathname, and, if there was a
+previous current pathname, the alternate pathname. The commands
+.BR :write ,
+.BR !command ,
+and
+.BR :edit
+set neither the current or alternate pathnames. If the
+.BR ":edit foo"
+command were to fail for some reason, the alternate pathname would be
+set. The
+.BR read
+and
+.BR write
+commands set the alternate pathname to their
+.IR file
+argument, unless the current pathname is not set, in which case they
+set the current pathname to their
+.IR file
+arguments. The alternate pathname was not historically set by the
+.BR :source
+command. POSIX.1\(hy2008 requires conformance to historical practice.
+Implementations adding commands that take filenames as arguments are
+encouraged to set the alternate pathname as described here.
+.P
+Historically,
+.IR ex
+and
+.IR vi
+read the
+.BR .exrc
+file in the
+.IR $HOME
+directory twice, if the editor was executed in the
+.IR $HOME
+directory. POSIX.1\(hy2008 prohibits this behavior.
+.P
+Historically, the 4 BSD
+.IR ex
+and
+.IR vi
+read the
+.IR $HOME
+and local
+.BR .exrc
+files if they were owned by the real ID of the user, or the
+.BR sourceany
+option was set, regardless of other considerations. This was a security
+problem because it is possible to put normal UNIX system commands
+inside a
+.BR .exrc
+file. POSIX.1\(hy2008 does not specify the
+.BR sourceany
+option, and historical implementations are encouraged to delete it.
+.P
+The
+.BR .exrc
+files must be owned by the real ID of the user, and not writable by
+anyone other than the owner. The appropriate privileges exception is
+intended to permit users to acquire special privileges, but continue to
+use the
+.BR .exrc
+files in their home directories.
+.P
+System V Release 3.2 and later
+.IR vi
+implementations added the option
+.BR [no]exrc .
+The behavior is that local
+.BR .exrc
+files are read-only if the
+.BR exrc
+option is set. The default for the
+.BR exrc
+option was off, so by default, local
+.BR .exrc
+files were not read. The problem this was intended to solve was that
+System V permitted users to give away files, so there is no possible
+ownership or writeability test to ensure that the file is safe. This is
+still a security problem on systems where users can give away files,
+but there is nothing additional that POSIX.1\(hy2008 can do. The
+implementation-defined exception is intended to permit groups to have
+local
+.BR .exrc
+files that are shared by users, by creating pseudo-users to own the
+shared files.
+.P
+POSIX.1\(hy2008 does not mention system-wide
+.IR ex
+and
+.IR vi
+start-up files. While they exist in several implementations of
+.IR ex
+and
+.IR vi ,
+they are not present in any implementations considered historical
+practice by POSIX.1\(hy2008. Implementations that have such files should use them
+only if they are owned by the real user ID or an appropriate user (for
+example, root on UNIX systems) and if they are not writable by any
+user other than their owner. System-wide start-up files should be read
+before the
+.IR EXINIT
+variable,
+.BR $HOME/.exrc ,
+or local
+.BR .exrc
+files are evaluated.
+.P
+Historically, any
+.IR ex
+command could be entered in the
+.IR EXINIT
+variable or the
+.BR .exrc
+file, although ones requiring that the edit buffer already contain
+lines of text generally caused historical implementations of the editor
+to drop
+.BR core .
+POSIX.1\(hy2008 requires that any
+.IR ex
+command be permitted in the
+.IR EXINIT
+variable and
+.BR .exrc
+files, for simplicity of specification and consistency, although many
+of them will obviously fail under many circumstances.
+.P
+The initialization of the contents of the edit buffer uses the phrase
+``the effect shall be'' with regard to various
+.IR ex
+commands. The intent of this phrase is that edit buffer contents loaded
+during the initialization phase not be lost; that is, loading the edit
+buffer should fail if the
+.BR .exrc
+file read in the contents of a file and did not subsequently write the
+edit buffer. An additional intent of this phrase is to specify that the
+initial current line and column is set as specified for the individual
+.IR ex
+commands.
+.P
+Historically, the
+.BR \-t
+option behaved as if the tag search were a
+.BR + \c
+.IR command ;
+that is, it was executed from the last line of the file specified by
+the tag. This resulted in the search failing if the pattern was a
+forward search pattern and the
+.BR wrapscan
+edit option was not set. POSIX.1\(hy2008 does not permit this behavior, requiring
+that the search for the tag pattern be performed on the entire file,
+and, if not found, that the current line be set to a more reasonable
+location in the file.
+.P
+Historically, the empty edit buffer presented for editing when a file
+was not specified by the user was unnamed. This is permitted by POSIX.1\(hy2008;
+however, implementations are encouraged to provide users a temporary
+filename for this buffer because it permits them the use of
+.IR ex
+commands that use the current pathname during temporary edit
+sessions.
+.P
+Historically, the file specified using the
+.BR \-t
+option was not part of the current argument list. This practice is
+permitted by POSIX.1\(hy2008; however, implementations are encouraged to include
+its name in the current argument list for consistency.
+.P
+Historically, the
+.BR \-c
+command was generally not executed until a file that already exists was
+edited. POSIX.1\(hy2008 requires conformance to this historical practice.
+Commands that could cause the
+.BR \-c
+command to be executed include the
+.IR ex
+commands
+.BR edit ,
+.BR next ,
+.BR recover ,
+.BR rewind ,
+and
+.BR tag ,
+and the
+.IR vi
+commands
+<control>\(hy^
+and
+<control>\(hy].
+Historically, reading a file into an edit buffer did not cause the
+.BR \-c
+command to be executed (even though it might set the current pathname)
+with the exception that it did cause the
+.BR \-c
+command to be executed if: the editor was in
+.IR ex
+mode, the edit buffer had no current pathname, the edit buffer was
+empty, and no read commands had yet been attempted. For consistency and
+simplicity of specification, POSIX.1\(hy2008 does not permit this behavior.
+.P
+Historically, the
+.BR \-r
+option was the same as a normal edit session if there was no recovery
+information available for the file. This allowed users to enter:
+.sp
+.RS 4
+.nf
+
+vi -r *.c
+.fi
+.P
+.RE
+.P
+and recover whatever files were recoverable. In some implementations,
+recovery was attempted only on the first file named, and the file was
+not entered into the argument list; in others, recovery was attempted
+for each file named. In addition, some historical implementations
+ignored
+.BR \-r
+if
+.BR \-t
+was specified or did not support command line
+.IR file
+arguments with the
+.BR \-t
+option. For consistency and simplicity of specification, POSIX.1\(hy2008
+disallows these special cases, and requires that recovery be attempted
+the first time each file is edited.
+.P
+Historically,
+.IR vi
+initialized the
+.BR `
+and
+.BR \(aq
+marks, but
+.IR ex
+did not. This meant that if the first command in
+.IR ex
+mode was
+.BR visual
+or if an
+.IR ex
+command was executed first (for example,
+.IR vi
++10
+.IR file ),
+.IR vi
+was entered without the marks being initialized. Because the standard
+developers believed the marks to be generally useful, and for
+consistency and simplicity of specification, POSIX.1\(hy2008 requires that they
+always be initialized if in open or visual mode, or if in
+.IR ex
+mode and the edit buffer is not empty. Not initializing it in
+.IR ex
+mode if the edit buffer is empty is historical practice; however, it
+has always been possible to set (and use) marks in empty edit buffers
+in open and visual mode edit sessions.
+.SS "Addressing"
+.P
+Historically,
+.IR ex
+and
+.IR vi
+accepted the additional addressing forms
+.BR '\e/' 
+and
+.BR '\e?' .
+They were equivalent to
+.BR \(dq//\(dq 
+and
+.BR \(dq??\(dq ,
+respectively. They are not required by POSIX.1\(hy2008, mostly because nobody can
+remember whether they ever did anything different historically.
+.P
+Historically,
+.IR ex
+and
+.IR vi
+permitted an address of zero for several commands, and permitted the
+.BR %
+address in empty files for others. For consistency, POSIX.1\(hy2008 requires
+support for the former in the few commands where it makes sense, and
+disallows it otherwise. In addition, because POSIX.1\(hy2008 requires that
+.BR %
+be logically equivalent to
+.BR \(dq1,$\(dq ,
+it is also supported where it makes sense and disallowed otherwise.
+.P
+Historically, the
+.BR %
+address could not be followed by further addresses. For consistency and
+simplicity of specification, POSIX.1\(hy2008 requires that additional addresses
+be supported.
+.P
+All of the following are valid
+.IR addresses :
+.IP "\fR+++\fP" 10
+Three lines after the current line.
+.IP "\fR/\fIre\fR/\-\fR" 10
+One line before the next occurrence of
+.IR re .
+.IP "\fR\-2\fR" 10
+Two lines before the current line.
+.IP "\fR3\0\-\|\-\|\-\|\-\02\fR" 10
+Line one (note intermediate negative address).
+.IP "\fR1\02\03\fR" 10
+Line six.
+.P
+Any number of addresses can be provided to commands taking addresses;
+for example,
+.BR \(dq1,2,3,4,5p\(dq 
+prints lines 4 and 5, because two is the greatest valid number of
+addresses accepted by the
+.BR print
+command. This, in combination with the
+<semicolon>
+delimiter, permits users to create commands based on ordered patterns
+in the file. For example, the command
+.BR "3;/foo/;+2print"
+will display the first line after line 3 that contains the pattern
+.IR foo ,
+plus the next two lines. Note that the address
+.BR "3;"
+must be evaluated before being discarded because the search origin for
+the
+.BR /foo/
+command depends on this.
+.P
+Historically, values could be added to addresses by including them
+after one or more
+<blank>
+characters; for example,
+.BR "3\0\-\05p"
+wrote the seventh line of the file, and
+.BR "/foo/\05"
+was the same as
+.BR "/foo/+5" .
+However, only absolute values could be added; for example,
+.BR "5\0/foo/"
+was an error. POSIX.1\(hy2008 requires conformance to historical practice.
+Address offsets are separately specified from addresses because they
+could historically be provided to visual mode search commands.
+.P
+Historically, any missing addresses defaulted to the current line. This
+was true for leading and trailing
+<comma>-delimited
+addresses, and for trailing
+<semicolon>-delimited
+addresses. For consistency, POSIX.1\(hy2008 requires it for leading
+<semicolon>
+addresses as well.
+.P
+Historically,
+.IR ex
+and
+.IR vi
+accepted the
+.BR '\(ha' 
+character as both an address and as a flag offset for commands. In both
+cases it was identical to the
+.BR '\-' 
+character. POSIX.1\(hy2008 does not require or prohibit this behavior.
+.P
+Historically, the enhancements to basic regular expressions could be
+used in addressing; for example,
+.BR '\(ti' ,
+.BR '\e<' ,
+and
+.BR '\e>' .
+POSIX.1\(hy2008 requires conformance to historical practice; that is, that
+regular expression usage be consistent, and that regular expression
+enhancements be supported wherever regular expressions are used.
+.SS "Command Line Parsing in ex"
+.P
+Historical
+.IR ex
+command parsing was even more complex than that described here. POSIX.1\(hy2008
+requires the subset of the command parsing that the standard developers
+believed was documented and that users could reasonably be expected to
+use in a portable fashion, and that was historically consistent between
+implementations. (The discarded functionality is obscure, at best.)
+Historical implementations will require changes in order to comply with
+POSIX.1\(hy2008; however, users are not expected to notice any of these changes.
+Most of the complexity in
+.IR ex
+parsing is to handle three special termination cases:
+.IP " 1." 4
+The
+.BR ! ,
+.BR global ,
+.BR v ,
+and the filter versions of the
+.BR read
+and
+.BR write
+commands are delimited by
+<newline>
+characters (they can contain
+<vertical-line>
+characters that are usually shell pipes).
+.IP " 2." 4
+The
+.BR ex ,
+.BR edit ,
+.BR next ,
+and
+.BR visual
+in open and visual mode commands all take
+.IR ex
+commands, optionally containing
+<vertical-line>
+characters, as their first arguments.
+.IP " 3." 4
+The
+.BR s
+command takes a regular expression as its first argument, and uses the
+delimiting characters to delimit the command.
+.P
+Historically,
+<vertical-line>
+characters in the
+.BR + \c
+.IR command
+argument of the
+.BR ex ,
+.BR edit ,
+.BR next ,
+.BR vi ,
+and
+.BR visual
+commands, and in the
+.IR pattern
+and
+.IR replacement
+parts of the
+.BR s
+command, did not delimit the command, and in the filter cases for
+.BR read
+and
+.BR write ,
+and the
+.BR ! ,
+.BR global ,
+and
+.BR v
+commands, they did not delimit the command at all. For example, the
+following commands are all valid:
+.sp
+.RS 4
+.nf
+
+\fB:\fRedit +25 | s/abc/ABC/ file.c
+\fB:\fRs/ | /PIPE/
+\fB:\fRread !spell % | columnate
+\fB:\fRglobal/pattern/p | l
+\fB:\fRs/a/b/ | s/c/d | set
+.fi
+.P
+.RE
+.P
+Historically, empty or
+<blank>
+filled lines in
+.BR .exrc
+files and
+.BR source d
+files (as well as
+.IR EXINIT
+variables and
+.IR ex
+command scripts) were treated as default commands; that is,
+.BR print
+commands. POSIX.1\(hy2008 specifically requires that they be ignored when
+encountered in
+.BR .exrc
+and
+.BR source d
+files to eliminate a common source of new user error.
+.P
+Historically,
+.IR ex
+commands with multiple adjacent (or
+<blank>-separated)
+vertical lines were handled oddly when executed from
+.IR ex
+mode. For example, the command
+.BR "|||"
+<carriage-return>,
+when the cursor was on line 1, displayed lines 2, 3, and 5 of the file.
+In addition, the command
+.BR |
+would only display the line after the next line, instead of the next
+two lines. The former worked more logically when executed from
+.IR vi
+mode, and displayed lines 2, 3, and 4. POSIX.1\(hy2008 requires the
+.IR vi
+behavior; that is, a single default command and line number increment
+for each command separator, and trailing
+<newline>
+characters after
+<vertical-line>
+separators are discarded.
+.P
+Historically,
+.IR ex
+permitted a single extra
+<colon>
+as a leading command character; for example,
+.BR ":g/pattern/:p"
+was a valid command. POSIX.1\(hy2008 generalizes this to require that any number
+of leading
+<colon>
+characters be stripped.
+.P
+Historically, any prefix of the
+.BR delete
+command could be followed without intervening
+<blank>
+characters by a flag character because in the command
+.BR "d\0p" ,
+.IR p
+is interpreted as the buffer
+.IR p .
+POSIX.1\(hy2008 requires conformance to historical practice.
+.P
+Historically, the
+.BR k
+command could be followed by the mark name without intervening
+<blank>
+characters. POSIX.1\(hy2008 requires conformance to historical practice.
+.P
+Historically, the
+.BR s
+command could be immediately followed by flag and option characters;
+for example,
+.BR "s/e/E/|s|sgc3p"
+was a valid command. However, flag characters could not stand alone;
+for example, the commands
+.BR sp
+and
+.BR s\0l
+would fail, while the command
+.BR sgp
+and
+.BR "s\0gl"
+would succeed. (Obviously, the
+.BR '#' 
+flag character was used as a delimiter character if it followed the
+command.) Another issue was that option characters had to precede flag
+characters even when the command was fully specified; for example, the
+command
+.BR s/e/E/pg
+would fail, while the command
+.BR s/e/E/gp
+would succeed. POSIX.1\(hy2008 requires conformance to historical practice.
+.P
+Historically, the first command name that had a prefix matching the
+input from the user was the executed command; for example,
+.BR ve ,
+.BR ver ,
+and
+.BR vers
+all executed the
+.BR version
+command. Commands were in a specific order, however, so that
+.BR a
+matched
+.BR append ,
+not
+.BR abbreviate .
+POSIX.1\(hy2008 requires conformance to historical practice. The restriction on
+command search order for implementations with extensions is to avoid
+the addition of commands such that the historical prefixes would fail
+to work portably.
+.P
+Historical implementations of
+.IR ex
+and
+.IR vi
+did not correctly handle multiple
+.IR ex
+commands, separated by
+<vertical-line>
+characters, that entered or exited visual mode or the editor. Because
+implementations of
+.IR vi
+exist that do not exhibit this failure mode, POSIX.1\(hy2008 does not permit it.
+.P
+The requirement that alphabetic command names consist of all following
+alphabetic characters up to the next non-alphabetic character means
+that alphabetic command names must be separated from their arguments by
+one or more non-alphabetic characters, normally a
+<blank>
+or
+.BR '!' 
+character, except as specified for the exceptions, the
+.BR delete ,
+.BR k ,
+and
+.BR s
+commands.
+.P
+Historically, the repeated execution of the
+.IR ex
+default
+.BR print
+commands (\c
+<control>\(hyD,
+.IR eof ,
+<newline>,
+<carriage-return>)
+erased any prompting character and displayed the next lines without
+scrolling the terminal; that is, immediately below any previously
+displayed lines. This provided a cleaner presentation of the lines in
+the file for the user. POSIX.1\(hy2008 does not require this behavior because it
+may be impossible in some situations; however, implementations are
+strongly encouraged to provide this semantic if possible.
+.P
+Historically, it was possible to change files in the middle of a command,
+and have the rest of the command executed in the new file; for example:
+.sp
+.RS 4
+.nf
+
+:edit +25 file.c | s/abc/ABC/ | 1
+.fi
+.P
+.RE
+.P
+was a valid command, and the substitution was attempted in the newly
+edited file. POSIX.1\(hy2008 requires conformance to historical practice. The
+following commands are examples that exercise the
+.IR ex
+parser:
+.sp
+.RS 4
+.nf
+
+echo \(aqfoo | bar\(aq > file1; echo \(aqfoo/bar\(aq > file2;
+vi
+:edit +1 | s/|/PIPE/ | w file1 | e file2 | 1 | s/\e//SLASH/ | wq
+.fi
+.P
+.RE
+.P
+Historically, there was no protection in editor implementations to
+avoid
+.IR ex
+.BR global ,
+.BR v ,
+.BR @ ,
+or
+.BR *
+commands changing edit buffers during execution of their associated
+commands. Because this would almost invariably result in catastrophic
+failure of the editor, and implementations exist that do exhibit these
+problems, POSIX.1\(hy2008 requires that changing the edit buffer during a
+.BR global
+or
+.BR v
+command, or during a
+.BR @
+or
+.BR *
+command for which there will be more than a single execution, be an
+error. Implementations supporting multiple edit buffers simultaneously
+are strongly encouraged to apply the same semantics to switching
+between buffers as well.
+.P
+The
+.IR ex
+command quoting required by POSIX.1\(hy2008 is a superset of the quoting in
+historical implementations of the editor. For example, it was not
+historically possible to escape a
+<blank>
+in a filename; for example,
+.BR ":edit\0foo\e\e\e\0bar"
+would report that too many filenames had been entered for the edit
+command, and there was no method of escaping a
+<blank>
+in the first argument of an
+.BR edit ,
+.BR ex ,
+.BR next ,
+or
+.BR visual
+command at all. POSIX.1\(hy2008 extends historical practice, requiring that
+quoting behavior be made consistent across all
+.IR ex
+commands, except for the
+.BR map ,
+.BR unmap ,
+.BR abbreviate ,
+and
+.BR unabbreviate
+commands, which historically used
+<control>\(hyV
+instead of
+<backslash>
+characters for quoting. For those four commands, POSIX.1\(hy2008 requires
+conformance to historical practice.
+.P
+Backslash quoting in
+.IR ex
+is non-intuitive.
+<backslash>-escapes
+are ignored unless they escape a special character; for example, when
+performing
+.IR file
+argument expansion, the string
+.BR \(dq\e\e%\(dq 
+is equivalent to
+.BR '\e%' ,
+not \fR"\e<\fIcurrent\ pathname\fR>"\fR.
+This can be confusing for users because
+<backslash>
+is usually one of the characters that causes shell expansion to
+be performed, and therefore shell quoting rules must be taken into
+consideration. Generally, quoting characters are only considered if they
+escape a special character, and a quoting character must be provided
+for each layer of parsing for which the character is special. As another
+example, only a single
+<backslash>
+is necessary for the
+.BR '\el' 
+sequence in substitute replacement patterns, because the character
+.BR 'l' 
+is not special to any parsing layer above it.
+.P
+<control>\(hyV
+quoting in
+.IR ex
+is slightly different from backslash quoting. In the four commands
+where
+<control>\(hyV
+quoting applies (\c
+.BR abbreviate ,
+.BR unabbreviate ,
+.BR map ,
+and
+.BR unmap ),
+any character may be escaped by a
+<control>\(hyV
+whether it would have a special meaning or not. POSIX.1\(hy2008 requires
+conformance to historical practice.
+.P
+Historical implementations of the editor did not require delimiters
+within character classes to be escaped; for example, the command
+.BR ":s/[/]//"
+on the string
+.BR \(dqxxx/yyy\(dq 
+would delete the
+.BR '/' 
+from the string. POSIX.1\(hy2008 disallows this historical practice for
+consistency and because it places a large burden on implementations by
+requiring that knowledge of regular expressions be built into the
+editor parser.
+.P
+Historically, quoting
+<newline>
+characters in
+.IR ex
+commands was handled inconsistently. In most cases, the
+<newline>
+character always terminated the command, regardless of any preceding
+escape character, because
+<backslash>
+characters did not escape
+<newline>
+characters for most
+.IR ex
+commands. However, some
+.IR ex
+commands (for example,
+.BR s ,
+.BR map ,
+and
+.BR abbreviation )
+permitted
+<newline>
+characters to be escaped (although in the case of
+.BR map
+and
+.BR abbreviation ,
+<control>\(hyV
+characters escaped them instead of
+<backslash>
+characters). This was true in not only the command line, but also
+.BR .exrc
+and
+.BR source d
+files. For example, the command:
+.sp
+.RS 4
+.nf
+
+map = foo<control-V><newline>bar
+.fi
+.P
+.RE
+.P
+would succeed, although it was sometimes difficult to get the
+<control>\(hyV
+and the inserted
+<newline>
+passed to the
+.IR ex
+parser. For consistency and simplicity of specification, POSIX.1\(hy2008 requires
+that it be possible to escape
+<newline>
+characters in
+.IR ex
+commands at all times, using
+<backslash>
+characters for most
+.IR ex
+commands, and using
+<control>\(hyV
+characters for the
+.BR map
+and
+.BR abbreviation
+commands. For example, the command
+.BR print \c
+<newline>\c
+.BR list
+is required to be parsed as the single command
+.BR print \c
+<newline>\c
+.BR list .
+While this differs from historical practice, POSIX.1\(hy2008 developers believed
+it unlikely that any script or user depended on the historical
+behavior.
+.P
+Historically, an error in a command specified using the
+.BR \-c
+option did not cause the rest of the
+.BR \-c
+commands to be discarded. POSIX.1\(hy2008 disallows this for consistency with
+mapped keys, the
+.BR @ ,
+.BR global ,
+.BR source ,
+and
+.BR v
+commands, the
+.IR EXINIT
+environment variable, and the
+.BR .exrc
+files.
+.SS "Input Editing in ex"
+.P
+One of the common uses of the historical
+.IR ex
+editor is over slow network connections. Editors that run in canonical
+mode can require far less traffic to and from, and far less processing
+on, the host machine, as well as more easily supporting block-mode
+terminals. For these reasons, POSIX.1\(hy2008 requires that
+.IR ex
+be implemented using canonical mode input processing, as was done
+historically.
+.P
+POSIX.1\(hy2008 does not require the historical 4 BSD input editing characters
+``word erase'' or ``literal next''. For this reason, it is unspecified
+how they are handled by
+.IR ex ,
+although they must have the required effect. Implementations that
+resolve them after the line has been ended using a
+<newline>
+or
+<control>\(hyM
+character, and implementations that rely on the underlying system
+terminal support for this processing, are both conforming.
+Implementations are strongly urged to use the underlying system
+functionality, if at all possible, for compatibility with other system
+text input interfaces.
+.P
+Historically, when the
+.IR eof
+character was used to decrement the
+.BR autoindent
+level, the cursor moved to display the new end of the
+.BR autoindent
+characters, but did not move the cursor to a new line, nor did it erase
+the
+<control>\(hyD
+character from the line. POSIX.1\(hy2008 does not specify that the cursor remain
+on the same line or that the rest of the line is erased; however,
+implementations are strongly encouraged to provide the best possible
+user interface; that is, the cursor should remain on the same line, and
+any
+<control>\(hyD
+character on the line should be erased.
+.P
+POSIX.1\(hy2008 does not require the historical 4 BSD input editing character
+``reprint'', traditionally
+<control>\(hyR,
+which redisplayed the current input from the user. For this reason, and
+because the functionality cannot be implemented after the line has been
+terminated by the user, POSIX.1\(hy2008 makes no requirements about this
+functionality. Implementations are strongly urged to make this
+historical functionality available, if possible.
+.P
+Historically,
+<control>\(hyQ
+did not perform a literal next function in
+.IR ex ,
+as it did in
+.IR vi .
+POSIX.1\(hy2008 requires conformance to historical practice to avoid breaking
+historical
+.IR ex
+scripts and
+.BR .exrc
+files.
+.SS "eof"
+.P
+Whether the
+.IR eof
+character immediately modifies the
+.BR autoindent
+characters in the prompt is left unspecified so that implementations
+can conform in the presence of systems that do not support this
+functionality. Implementations are encouraged to modify the line and
+redisplay it immediately, if possible.
+.P
+The specification of the handling of the
+.IR eof
+character differs from historical practice only in that
+.IR eof
+characters are not discarded if they follow normal characters in the
+text input. Historically, they were always discarded.
+.SS "Command Descriptions in ex"
+.P
+Historically, several commands (for example,
+.BR global ,
+.BR v ,
+.BR visual ,
+.BR s ,
+.BR write ,
+.BR wq ,
+.BR yank ,
+.BR ! ,
+.BR < ,
+.BR > ,
+.BR & ,
+and
+.BR ~ )
+were executable in empty files (that is, the default address(es) were
+0), or permitted explicit addresses of 0 (for example, 0 was a valid
+address, or 0,0 was a valid range). Addresses of 0, or command
+execution in an empty file, make sense only for commands that add new
+text to the edit buffer or write commands (because users may wish to
+write empty files). POSIX.1\(hy2008 requires this behavior for such commands and
+disallows it otherwise, for consistency and simplicity of
+specification.
+.P
+A count to an
+.IR ex
+command has been historically corrected to be no greater than the last
+line in a file; for example, in a five-line file, the command
+.BR "1,6print"
+would fail, but the command
+.BR "1print300"
+would succeed. POSIX.1\(hy2008 requires conformance to historical practice.
+.P
+Historically, the use of flags in
+.IR ex
+commands could be obscure. General historical practice was as described
+by POSIX.1\(hy2008, but there were some special cases. For instance, the
+.BR list ,
+.BR number ,
+and
+.BR print
+commands ignored trailing address offsets; for example,
+.BR "3p\0+++#"
+would display line 3, and 3 would be the current line after the
+execution of the command. The
+.BR open
+and
+.BR visual
+commands ignored both the trailing offsets and the trailing flags.
+Also, flags specified to the
+.BR open
+and
+.BR visual
+commands interacted badly with the
+.BR list
+edit option, and setting and then unsetting it during the open/visual
+session would cause
+.IR vi
+to stop displaying lines in the specified format. For consistency and
+simplicity of specification, POSIX.1\(hy2008 does not permit any of these
+exceptions to the general rule.
+.P
+POSIX.1\(hy2008 uses the word
+.IR copy
+in several places when discussing buffers. This is not intended to
+imply implementation.
+.P
+Historically,
+.IR ex
+users could not specify numeric buffers because of the ambiguity this
+would cause; for example, in the command
+.BR "3\0delete\02" ,
+it is unclear whether 2 is a buffer name or a
+.IR count .
+POSIX.1\(hy2008 requires conformance to historical practice by default, but does
+not preclude extensions.
+.P
+Historically, the contents of the unnamed buffer were frequently
+discarded after commands that did not explicitly affect it; for
+example, when using the
+.BR edit
+command to switch files. For consistency and simplicity of
+specification, POSIX.1\(hy2008 does not permit this behavior.
+.P
+The
+.IR ex
+utility did not historically have access to the numeric buffers, and,
+furthermore, deleting lines in
+.IR ex
+did not modify their contents. For example, if, after doing a delete in
+.IR vi ,
+the user switched to
+.IR ex ,
+did another delete, and then switched back to
+.IR vi ,
+the contents of the numeric buffers would not have changed. POSIX.1\(hy2008
+requires conformance to historical practice. Numeric buffers are
+described in the
+.IR ex
+utility in order to confine the description of buffers to a single
+location in POSIX.1\(hy2008.
+.P
+The metacharacters that trigger shell expansion in
+.IR file
+arguments match historical practice, as does the method for doing shell
+expansion. Implementations wishing to provide users with the
+flexibility to alter the set of metacharacters are encouraged to
+provide a
+.BR shellmeta
+string edit option.
+.P
+Historically,
+.IR ex
+commands executed from
+.IR vi
+refreshed the screen when it did not strictly need to do so; for
+example,
+.BR ":!date\0>\0/dev/null"
+does not require a screen refresh because the output of the UNIX
+.IR date
+command requires only a single line of the screen. POSIX.1\(hy2008 requires that
+the screen be refreshed if it has been overwritten, but makes no
+requirements as to how an implementation should make that
+determination. Implementations may prompt and refresh the screen
+regardless.
+.SS "Abbreviate"
+.P
+Historical practice was that characters that were entered as part of an
+abbreviation replacement were subject to
+.BR map
+expansions, the
+.BR showmatch
+edit option, further abbreviation expansions, and so on; that is, they
+were logically pushed onto the terminal input queue, and were not a
+simple replacement. POSIX.1\(hy2008 requires conformance to historical practice.
+Historical practice was that whenever a non-word character (that had
+not been escaped by a
+<control>\(hyV)
+was entered after a word character,
+.IR vi
+would check for abbreviations. The check was based on the type of the
+character entered before the word character of the word/non-word pair
+that triggered the check. The word character of the word/non-word pair
+that triggered the check and all characters entered before the trigger
+pair that were of that type were included in the check, with the
+exception of
+<blank>
+characters, which always delimited the abbreviation.
+.P
+This means that, for the abbreviation to work, the
+.IR lhs
+must end with a word character, there can be no transitions from word
+to non-word characters (or \fIvice versa\fP) other than between the
+last and next-to-last characters in the
+.IR lhs ,
+and there can be no
+<blank>
+characters in the
+.IR lhs .
+In addition, because of the historical quoting rules, it was impossible
+to enter a literal
+<control>\(hyV
+in the
+.IR lhs .
+POSIX.1\(hy2008 requires conformance to historical practice. Historical
+implementations did not inform users when abbreviations that could
+never be used were entered; implementations are strongly encouraged to
+do so.
+.br
+.P
+For example, the following abbreviations will work:
+.sp
+.RS 4
+.nf
+
+:ab (p  REPLACE
+:ab p   REPLACE
+:ab ((p REPLACE
+.fi
+.P
+.RE
+.P
+The following abbreviations will not work:
+.sp
+.RS 4
+.nf
+
+:ab (   REPLACE
+:ab (pp REPLACE
+.fi
+.P
+.RE
+.P
+Historical practice is that words on the
+.IR vi
+colon command line were subject to abbreviation expansion, including
+the arguments to the
+.BR abbrev
+(and more interestingly) the
+.BR unabbrev
+command. Because there are implementations that do not do abbreviation
+expansion for the first argument to those commands, this is permitted,
+but not required, by POSIX.1\(hy2008. However, the following sequence:
+.sp
+.RS 4
+.nf
+
+:ab foo bar
+:ab foo baz
+.fi
+.P
+.RE
+.P
+resulted in the addition of an abbreviation of
+.BR \(dqbaz\(dq 
+for the string
+.BR \(dqbar\(dq 
+in historical
+.IR ex /\c
+.IR vi ,
+and the sequence:
+.sp
+.RS 4
+.nf
+
+:ab foo1 bar
+:ab foo2 bar
+:unabbreviate foo2
+.fi
+.P
+.RE
+.P
+deleted the abbreviation
+.BR \(dqfoo1\(dq ,
+not
+.BR \(dqfoo2\(dq .
+These behaviors are not permitted by POSIX.1\(hy2008 because they clearly violate
+the expectations of the user.
+.P
+It was historical practice that
+<control>\(hyV,
+not
+<backslash>,
+characters be interpreted as escaping subsequent characters in the
+.BR abbreviate
+command. POSIX.1\(hy2008 requires conformance to historical practice; however, it
+should be noted that an abbreviation containing a
+<blank>
+will never work.
+.SS "Append"
+.P
+Historically, any text following a
+<vertical-line>
+command separator after an
+.BR append ,
+.BR change ,
+or
+.BR insert
+command became part of the insert text. For example, in the command:
+.sp
+.RS 4
+.nf
+
+:g/pattern/append|stuff1
+.fi
+.P
+.RE
+.P
+a line containing the text
+.BR \(dqstuff1\(dq 
+would be appended to each line matching pattern. It was also
+historically valid to enter:
+.sp
+.RS 4
+.nf
+
+:append|stuff1
+stuff2
+\&.
+.fi
+.P
+.RE
+.P
+and the text on the
+.IR ex
+command line would be appended along with the text inserted after it.
+There was an historical bug, however, that the user had to enter two
+terminating lines (the
+.BR '.' 
+lines) to terminate text input mode in this case. POSIX.1\(hy2008 requires
+conformance to historical practice, but disallows the historical need
+for multiple terminating lines.
+.SS "Change"
+.P
+See the RATIONALE for the
+.BR append
+command. Historical practice for cursor positioning after the change
+command when no text is input, is as described in POSIX.1\(hy2008. However, one
+System V implementation is known to have been modified such that the
+cursor is positioned on the first address specified, and not on the
+line before the first address. POSIX.1\(hy2008 disallows this modification for
+consistency.
+.P
+Historically, the
+.BR change
+command did not support buffer arguments, although some implementations
+allow the specification of an optional buffer. This behavior is neither
+required nor disallowed by POSIX.1\(hy2008.
+.SS "Change Directory"
+.P
+A common extension in
+.IR ex
+implementations is to use the elements of a
+.BR cdpath
+edit option as prefix directories for
+.IR path
+arguments to
+.BR chdir
+that are relative pathnames and that do not have
+.BR '.' 
+or
+.BR \(dq..\(dq 
+as their first component. Elements in the
+.BR cdpath
+edit option are
+<colon>-separated.
+The initial value of the
+.BR cdpath
+edit option is the value of the shell
+.IR CDPATH
+environment variable. This feature was not included in POSIX.1\(hy2008 because it
+does not exist in any of the implementations considered historical
+practice.
+.SS "Copy"
+.P
+Historical implementations of
+.IR ex
+permitted copies to lines inside of the specified range; for example,
+.BR ":2,5copy3"
+was a valid command. POSIX.1\(hy2008 requires conformance to historical
+practice.
+.SS "Delete"
+.P
+POSIX.1\(hy2008 requires support for the historical parsing of a
+.BR delete
+command followed by flags, without any intervening
+<blank>
+characters. For example:
+.IP "\fB1dp\fP" 8
+Deletes the first line and prints the line that was second.
+.IP "\fB1delep\fP" 8
+As for
+.BR 1dp .
+.IP "\fB1d\fP" 8
+Deletes the first line, saving it in buffer
+.IR p .
+.IP "\fB1d\0p1l\fP" 8
+(Pee-one-ell.) Deletes the first line, saving it in buffer
+.IR p ,
+and listing the line that was second.
+.SS "Edit"
+.P
+Historically, any
+.IR ex
+command could be entered as a
+.BR + \c
+.IR command
+argument to the
+.BR edit
+command, although some (for example,
+.BR insert
+and
+.BR append )
+were known to confuse historical implementations. For consistency and
+simplicity of specification, POSIX.1\(hy2008 requires that any command be
+supported as an argument to the
+.BR edit
+command.
+.P
+Historically, the command argument was executed with the current line
+set to the last line of the file, regardless of whether the
+.BR edit
+command was executed from visual mode or not. POSIX.1\(hy2008 requires
+conformance to historical practice.
+.P
+Historically, the
+.BR + \c
+.IR command
+specified to the
+.BR edit
+and
+.BR next
+commands was delimited by the first
+<blank>,
+and there was no way to quote them. For consistency, POSIX.1\(hy2008 requires
+that the usual
+.IR ex
+backslash quoting be provided.
+.P
+Historically, specifying the
+.BR + \c
+.IR command
+argument to the edit command required a filename to be specified as
+well; for example,
+.BR ":edit\0+100"
+would always fail. For consistency and simplicity of specification,
+POSIX.1\(hy2008 does not permit this usage to fail for that reason.
+.P
+Historically, only the cursor position of the last file edited was
+remembered by the editor. POSIX.1\(hy2008 requires that this be supported;
+however, implementations are permitted to remember and restore the
+cursor position for any file previously edited.
+.SS "File"
+.P
+Historical versions of the
+.IR ex
+editor
+.BR file
+command displayed a current line and number of lines in the edit buffer
+of 0 when the file was empty, while the
+.IR vi
+<control>\(hyG
+command displayed a current line and number of lines in the edit buffer
+of 1 in the same situation. POSIX.1\(hy2008 does not permit this discrepancy,
+instead requiring that a message be displayed indicating that the file
+is empty.
+.SS "Global"
+.P
+The two-pass operation of the
+.BR global
+and
+.BR v
+commands is not intended to imply implementation, only the required
+result of the operation.
+.P
+The current line and column are set as specified for the individual
+.IR ex
+commands. This requirement is cumulative; that is, the current line and
+column must track across all the commands executed by the
+.BR global
+or
+.BR v
+commands.
+.SS "Insert"
+.P
+See the RATIONALE for the
+.BR append
+command.
+.P
+Historically,
+.BR insert
+could not be used with an address of zero; that is, not when the edit
+buffer was empty. POSIX.1\(hy2008 requires that this command behave consistently
+with the
+.BR append
+command.
+.SS "Join"
+.P
+The action of the
+.BR join
+command in relation to the special characters is only defined for the
+POSIX locale because the correct amount of white space after a period
+varies; in Japanese none is required, in French only a single space,
+and so on.
+.SS "List"
+.P
+The historical output of the
+.BR list
+command was potentially ambiguous. The standard developers believed
+correcting this to be more important than adhering to historical
+practice, and POSIX.1\(hy2008 requires unambiguous output.
+.SS "Map"
+.P
+Historically, command mode maps only applied to command names; for
+example, if the character
+.BR 'x' 
+was mapped to
+.BR 'y' ,
+the command
+.BR fx
+searched for the
+.BR 'x' 
+character, not the
+.BR 'y' 
+character. POSIX.1\(hy2008 requires this behavior. Historically, entering
+<control>\(hyV
+as the first character of a
+.IR vi
+command was an error. Several implementations have extended the
+semantics of
+.IR vi
+such that
+<control>\(hyV
+means that the subsequent command character is not mapped. This is
+permitted, but not required, by POSIX.1\(hy2008. Regardless, using
+<control>\(hyV
+to escape the second or later character in a sequence of characters
+that might match a
+.BR map
+command, or any character in text input mode, is historical practice,
+and stops the entered keys from matching a map. POSIX.1\(hy2008 requires
+conformance to historical practice.
+.P
+Historical implementations permitted digits to be used as a
+.BR map
+command
+.IR lhs ,
+but then ignored the map. POSIX.1\(hy2008 requires that the mapped digits not be
+ignored.
+.P
+The historical implementation of the
+.BR map
+command did not permit
+.BR map
+commands that were more than a single character in length if the first
+character was printable. This behavior is permitted, but not required,
+by POSIX.1\(hy2008.
+.P
+Historically, mapped characters were remapped unless the
+.BR remap
+edit option was not set, or the prefix of the mapped characters matched
+the mapping characters; for example, in the
+.BR map :
+.sp
+.RS 4
+.nf
+
+:map ab abcd
+.fi
+.P
+.RE
+.P
+the characters
+.BR \(dqab\(dq 
+were used as is and were not remapped, but the characters
+.BR \(dqcd\(dq 
+were mapped if appropriate. This can cause infinite loops in the
+.IR vi
+mapping mechanisms. POSIX.1\(hy2008 requires conformance to historical practice,
+and that such loops be interruptible.
+.P
+Text input maps had the same problems with expanding the
+.IR lhs
+for the
+.IR ex
+.BR map!
+and
+.BR unmap!
+command as did the
+.IR ex
+.BR abbreviate
+and
+.BR unabbreviate
+commands. See the RATIONALE for the
+.IR ex
+.BR abbreviate
+command. POSIX.1\(hy2008 requires similar modification of some historical
+practice for the
+.BR map
+and
+.BR unmap
+commands, as described for the
+.BR abbreviate
+and
+.BR unabbreviate
+commands.
+.P
+Historically,
+.BR map s
+that were subsets of other
+.BR map s
+behaved differently depending on the order in which they were defined.
+For example:
+.sp
+.RS 4
+.nf
+
+:map! ab     short
+:map! abc    long
+.fi
+.P
+.RE
+.P
+would always translate the characters
+.BR \(dqab\(dq 
+to
+.BR \(dqshort\(dq ,
+regardless of how fast the characters
+.BR \(dqabc\(dq 
+were entered. If the entry order was reversed:
+.sp
+.RS 4
+.nf
+
+:map! abc    long
+:map! ab     short
+.fi
+.P
+.RE
+.P
+the characters
+.BR \(dqab\(dq 
+would cause the editor to pause, waiting for the completing
+.BR 'c' 
+character, and the characters might never be mapped to
+.BR \(dqshort\(dq .
+For consistency and simplicity of specification, POSIX.1\(hy2008 requires that
+the shortest match be used at all times.
+.P
+The length of time the editor spends waiting for the characters to
+complete the
+.IR lhs
+is unspecified because the timing capabilities of systems are often
+inexact and variable, and it may depend on other factors such as the
+speed of the connection. The time should be long enough for the user to
+be able to complete the sequence, but not long enough for the user to
+have to wait. Some implementations of
+.IR vi
+have added a
+.BR keytime
+option, which permits users to set the number of 0,1 seconds the editor
+waits for the completing characters. Because mapped terminal function
+and cursor keys tend to start with an
+<ESC>
+character, and
+<ESC>
+is the key ending
+.IR vi
+text input mode,
+.BR map s
+starting with
+<ESC>
+characters are generally exempted from this timeout period, or, at
+least timed out differently.
+.SS "Mark"
+.P
+Historically, users were able to set the ``previous context'' marks
+explicitly. In addition, the
+.IR ex
+commands
+.BR \(aq\(aq
+and
+.BR \(aq`
+and the
+.IR vi
+commands
+.BR \(aq\(aq ,
+.BR `` ,
+.BR `\(aq ,
+and
+.BR \(aq`
+all referred to the same mark. In addition, the previous context marks
+were not set if the command, with which the address setting the mark
+was associated, failed. POSIX.1\(hy2008 requires conformance to historical
+practice. Historically, if marked lines were deleted, the mark was also
+deleted, but would reappear if the change was undone. POSIX.1\(hy2008 requires
+conformance to historical practice.
+.P
+The description of the special events that set the
+.BR `
+and
+.BR \(aq
+marks matches historical practice. For example, historically the
+command
+.BR "/a/,/b/"
+did not set the
+.BR `
+and
+.BR \(aq
+marks, but the command
+.BR "/a/,/b/delete"
+did.
+.SS "Next"
+.P
+Historically, any
+.IR ex
+command could be entered as a
+.BR + \c
+.IR command
+argument to the
+.BR next
+command, although some (for example,
+.BR insert
+and
+.BR append )
+were known to confuse historical implementations. POSIX.1\(hy2008 requires that
+any command be permitted and that it behave as specified. The
+.BR next
+command can accept more than one file, so usage such as:
+.sp
+.RS 4
+.nf
+
+next `ls [abc] `
+.fi
+.P
+.RE
+.P
+is valid; it need not be valid for the
+.BR edit
+or
+.BR read
+commands, for example, because they expect only one filename.
+.P
+Historically, the
+.BR next
+command behaved differently from the
+.BR :rewind
+command in that it ignored the force flag if the
+.BR autowrite
+flag was set. For consistency, POSIX.1\(hy2008 does not permit this behavior.
+.P
+Historically, the
+.BR next
+command positioned the cursor as if the file had never been edited
+before, regardless. POSIX.1\(hy2008 does not permit this behavior, for
+consistency with the
+.BR edit
+command.
+.P
+Implementations wanting to provide a counterpart to the
+.BR next
+command that edited the previous file have used the command
+.BR prev[ious],
+which takes no
+.IR file
+argument. POSIX.1\(hy2008 does not require this command.
+.SS "Open"
+.P
+Historically, the
+.BR open
+command would fail if the
+.BR open
+edit option was not set. POSIX.1\(hy2008 does not mention the
+.BR open
+edit option and does not require this behavior. Some historical
+implementations do not permit entering open mode from open or visual
+mode, only from
+.IR ex
+mode. For consistency, POSIX.1\(hy2008 does not permit this behavior.
+.P
+Historically, entering open mode from the command line (that is,
+.IR vi
+.BR +open )
+resulted in anomalous behaviors; for example, the
+.IR ex
+file and
+.IR set
+commands, and the
+.IR vi
+command
+<control>\(hyG
+did not work. For consistency, POSIX.1\(hy2008 does not permit this behavior.
+.P
+Historically, the
+.BR open
+command only permitted
+.BR '/' 
+characters to be used as the search pattern delimiter. For consistency,
+POSIX.1\(hy2008 requires that the search delimiters used by the
+.BR s ,
+.BR global ,
+and
+.BR v
+commands be accepted as well.
+.SS "Preserve"
+.P
+The
+.BR preserve
+command does not historically cause the file to be considered
+unmodified for the purposes of future commands that may exit the
+editor. POSIX.1\(hy2008 requires conformance to historical practice.
+.P
+Historical documentation stated that mail was not sent to the user when
+preserve was executed; however, historical implementations did send
+mail in this case. POSIX.1\(hy2008 requires conformance to the historical
+implementations.
+.SS "Print"
+.P
+The writing of NUL by the
+.BR print
+command is not specified as a special case because the standard
+developers did not want to require
+.IR ex
+to support NUL characters. Historically, characters were displayed
+using the ARPA standard mappings, which are as follows:
+.IP " 1." 4
+Printable characters are left alone.
+.IP " 2." 4
+Control characters less than \e177 are represented as
+.BR '\(ha' 
+followed by the character offset from the
+.BR '@' 
+character in the ASCII map; for example, \e007 is represented as
+.BR '\(haG' .
+.IP " 3." 4
+\e177 is represented as
+.BR '\(ha' 
+followed by
+.BR '?' .
+.P
+The display of characters having their eighth bit set was less
+standard. Existing implementations use hex (0x00), octal (\e000), and a
+meta-bit display. (The latter displayed bytes that had their eighth bit
+set as the two characters
+.BR \(dqM-\(dq 
+followed by the seven-bit display as described above.) The latter
+probably has the best claim to historical practice because it was used
+for the
+.BR \-v
+option of 4 BSD and 4 BSD-derived versions of the
+.IR cat
+utility since 1980.
+.P
+No specific display format is required by POSIX.1\(hy2008.
+.P
+Explicit dependence on the ASCII character set has been avoided where
+possible, hence the use of the phrase an ``implementation-defined
+multi-character sequence'' for the display of non-printable characters
+in preference to the historical usage of, for instance,
+.BR \(dq\(haI\(dq 
+for the
+<tab>.
+Implementations are encouraged to conform to historical practice in the
+absence of any strong reason to diverge.
+.P
+Historically, all
+.IR ex
+commands beginning with the letter
+.BR 'p' 
+could be entered using capitalized versions of the commands; for
+example,
+.BR P[rint] ,
+.BR Pre[serve] ,
+and
+.BR Pu[t]
+were all valid command names. POSIX.1\(hy2008 permits, but does not require, this
+historical practice because capital forms of the commands are used by
+some implementations for other purposes.
+.SS "Put"
+.P
+Historically, an
+.IR ex
+.BR put
+command, executed from open or visual mode, was the same as the open or
+visual mode
+.BR P
+command, if the buffer was named and was cut in character mode, and the
+same as the
+.BR p
+command if the buffer was named and cut in line mode. If the unnamed
+buffer was the source of the text, the entire line from which the text
+was taken was usually
+.BR put ,
+and the buffer was handled as if in line mode, but it was possible to
+get extremely anomalous behavior. In addition, using the
+.BR Q
+command to switch into
+.IR ex
+mode, and then doing a
+.BR put
+often resulted in errors as well, such as appending text that was
+unrelated to the (supposed) contents of the buffer. For consistency and
+simplicity of specification, POSIX.1\(hy2008 does not permit these behaviors. All
+.IR ex
+.BR put
+commands are required to operate in line mode, and the contents of the
+buffers are not altered by changing the mode of the editor.
+.SS "Read"
+.P
+Historically, an
+.IR ex
+.BR read
+command executed from open or visual mode, executed in an empty file,
+left an empty line as the first line of the file. For consistency and
+simplicity of specification, POSIX.1\(hy2008 does not permit this behavior.
+Historically, a
+.BR read
+in open or visual mode from a program left the cursor at the last line
+read in, not the first. For consistency, POSIX.1\(hy2008 does not permit this
+behavior.
+.P
+Historical implementations of
+.IR ex
+were unable to undo
+.BR read
+commands that read from the output of a program. For consistency, POSIX.1\(hy2008
+does not permit this behavior.
+.P
+Historically, the
+.IR ex
+and
+.IR vi
+message after a successful
+.BR read
+or
+.BR write
+command specified ``characters'', not ``bytes''. POSIX.1\(hy2008 requires that
+the number of bytes be displayed, not the number of characters, because
+it may be difficult in multi-byte implementations to determine the
+number of characters read. Implementations are encouraged to clarify
+the message displayed to the user.
+.P
+Historically, reads were not permitted on files other than type
+regular, except that FIFO files could be read (probably only because
+they did not exist when
+.IR ex
+and
+.IR vi
+were originally written). Because the historical
+.IR ex
+evaluated
+.BR read!
+and
+.BR read\0!
+equivalently, there can be no optional way to force the read. POSIX.1\(hy2008
+permits, but does not require, this behavior.
+.SS "Recover"
+.P
+Some historical implementations of the editor permitted users to
+recover the edit buffer contents from a previous edit session, and then
+exit without saving those contents (or explicitly discarding them). The
+intent of POSIX.1\(hy2008 in requiring that the edit buffer be treated as already
+modified is to prevent this user error.
+.SS "Rewind"
+.P
+Historical implementations supported the
+.BR rewind
+command when the user was editing the first file in the list; that is,
+the file that the
+.BR rewind
+command would edit. POSIX.1\(hy2008 requires conformance to historical practice.
+.SS "Substitute"
+.P
+Historically,
+.IR ex
+accepted an
+.BR r
+option to the
+.BR s
+command. The effect of the
+.BR r
+option was to use the last regular expression used in any command as
+the pattern, the same as the
+.BR ~
+command. The
+.BR r
+option is not required by POSIX.1\(hy2008. Historically, the
+.BR c
+and
+.BR g
+options were toggled; for example, the command
+.BR ":s/abc/def/"
+was the same as
+.BR "s/abc/def/ccccgggg" .
+For simplicity of specification, POSIX.1\(hy2008 does not permit this behavior.
+.P
+The tilde command is often used to replace the last search RE. For
+example, in the sequence:
+.sp
+.RS 4
+.nf
+
+s/red/blue/
+/green
+\(ti
+.fi
+.P
+.RE
+.P
+the
+.BR ~
+command is equivalent to:
+.sp
+.RS 4
+.nf
+
+s/green/blue/
+.fi
+.P
+.RE
+.P
+Historically,
+.IR ex
+accepted all of the following forms:
+.sp
+.RS 4
+.nf
+
+s/abc/def/
+s/abc/def
+s/abc/
+s/abc
+.fi
+.P
+.RE
+.P
+POSIX.1\(hy2008 requires conformance to this historical practice.
+.P
+The
+.BR s
+command presumes that the
+.BR '\(ha' 
+character only occupies a single column in the display. Much of the
+.IR ex
+and
+.IR vi
+specification presumes that the
+<space>
+only occupies a single column in the display. There are no known
+character sets for which this is not true.
+.P
+Historically, the final column position for the substitute commands was
+based on previous column movements; a search for a pattern followed by
+a substitution would leave the column position unchanged, while a 0
+command followed by a substitution would change the column position to
+the first non-\c
+<blank>.
+For consistency and simplicity of specification, POSIX.1\(hy2008 requires that
+the final column position always be set to the first non-\c
+<blank>.
+.SS "Set"
+.P
+Historical implementations redisplayed all of the options for each
+occurrence of the
+.BR all
+keyword. POSIX.1\(hy2008 permits, but does not require, this behavior.
+.SS "Tag"
+.P
+No requirement is made as to where
+.IR ex
+and
+.IR vi
+shall look for the file referenced by the tag entry. Historical
+practice has been to look for the path found in the
+.BR tags
+file, based on the current directory. A useful extension found in some
+implementations is to look based on the directory containing the tags
+file that held the entry, as well. No requirement is made as to which
+reference for the tag in the tags file is used. This is deliberate, in
+order to permit extensions such as multiple entries in a tags file for
+a tag.
+.P
+Because users often specify many different tags files, some of which
+need not be relevant or exist at any particular time, POSIX.1\(hy2008 requires
+that error messages about problem tags files be displayed only if the
+requested tag is not found, and then, only once for each time that the
+.BR tag
+edit option is changed.
+.P
+The requirement that the current edit buffer be unmodified is only
+necessary if the file indicated by the tag entry is not the same as the
+current file (as defined by the current pathname). Historically, the
+file would be reloaded if the filename had changed, as well as if the
+filename was different from the current pathname. For consistency and
+simplicity of specification, POSIX.1\(hy2008 does not permit this behavior,
+requiring that the name be the only factor in the decision.
+.P
+Historically,
+.IR vi
+only searched for tags in the current file from the current cursor to
+the end of the file, and therefore, if the
+.BR wrapscan
+option was not set, tags occurring before the current cursor were not
+found. POSIX.1\(hy2008 considers this a bug, and implementations are required to
+search for the first occurrence in the file, regardless.
+.SS "Undo"
+.P
+The
+.BR undo
+description deliberately uses the word ``modified''. The
+.BR undo
+command is not intended to undo commands that replace the contents of
+the edit buffer, such as
+.BR edit ,
+.BR next ,
+.BR tag ,
+or
+.BR recover .
+.P
+Cursor positioning after the
+.BR undo
+command was inconsistent in the historical
+.IR vi ,
+sometimes attempting to restore the original cursor position (\c
+.BR global ,
+.BR undo ,
+and
+.BR v
+commands), and sometimes, in the presence of maps, placing the cursor
+on the last line added or changed instead of the first. POSIX.1\(hy2008 requires
+a simplified behavior for consistency and simplicity of specification.
+.SS "Version"
+.P
+The
+.BR version
+command cannot be exactly specified since there is no widely-accepted
+definition of what the version information should contain.
+Implementations are encouraged to do something reasonably intelligent.
+.SS "Write"
+.P
+Historically, the
+.IR ex
+and
+.IR vi
+message after a successful
+.BR read
+or
+.BR write
+command specified ``characters'', not ``bytes''. POSIX.1\(hy2008 requires that
+the number of bytes be displayed, not the number of characters because
+it may be difficult in multi-byte implementations to determine the
+number of characters written. Implementations are encouraged to clarify
+the message displayed to the user.
+.P
+Implementation-defined tests are permitted so that implementations
+can make additional checks; for example, for locks or file modification
+times.
+.P
+Historically, attempting to append to a nonexistent file caused an
+error. It has been left unspecified in POSIX.1\(hy2008 to permit implementations
+to let the
+.BR write
+succeed, so that the append semantics are similar to those of the
+historical
+.IR csh .
+.P
+Historical
+.IR vi
+permitted empty edit buffers to be written. However, since the way
+.IR vi
+got around dealing with ``empty'' files was to always have a line in
+the edit buffer, no matter what, it wrote them as files of a single,
+empty line. POSIX.1\(hy2008 does not permit this behavior.
+.P
+Historically,
+.IR ex
+restored standard output and standard error to their values as of when
+.IR ex
+was invoked, before writes to programs were performed. This could
+disturb the terminal configuration as well as be a security issue for
+some terminals. POSIX.1\(hy2008 does not permit this, requiring that the program
+output be captured and displayed as if by the
+.IR ex
+.BR print
+command.
+.SS "Adjust Window"
+.P
+Historically, the line count was set to the value of the
+.BR scroll
+option if the type character was end-of-file. This feature was broken
+on most historical implementations long ago, however, and is not
+documented anywhere. For this reason, POSIX.1\(hy2008 is resolutely silent.
+.P
+Historically, the
+.BR z
+command was
+<blank>-sensitive
+and
+.BR z\0+
+and
+.BR z\0\-
+did different things than
+.BR z+
+and
+.BR z\-
+because the type could not be distinguished from a flag. (The commands
+.BR z\0.
+and
+.BR z\0=
+were historically invalid.) POSIX.1\(hy2008 requires conformance to this
+historical practice.
+.P
+Historically, the
+.BR z
+command was further
+<blank>-sensitive
+in that the
+.IR count
+could not be
+<blank>-delimited;
+for example, the commands
+.BR z=\05
+and
+.BR z\-\05
+were also invalid. Because the
+.IR count
+is not ambiguous with respect to either the type character or the
+flags, this is not permitted by POSIX.1\(hy2008.
+.SS "Escape"
+.P
+Historically,
+.IR ex
+filter commands only read the standard output of the commands, letting
+standard error appear on the terminal as usual. The
+.IR vi
+utility, however, read both standard output and standard error. POSIX.1\(hy2008
+requires the latter behavior for both
+.IR ex
+and
+.IR vi ,
+for consistency.
+.SS "Shift Left and Shift Right"
+.P
+Historically, it was possible to add shift characters to increase the
+effect of the command; for example,
+.BR <<<
+outdented (or
+.BR >>>
+indented) the lines 3 levels of indentation instead of the default 1.
+POSIX.1\(hy2008 requires conformance to historical practice.
+.SS "<control>\(hyD"
+.P
+Historically, the
+<control>\(hyD
+command erased the prompt, providing the user with an unbroken
+presentation of lines from the edit buffer. This is not required by
+POSIX.1\(hy2008; implementations are encouraged to provide it if possible.
+Historically, the
+<control>\(hyD
+command took, and then ignored, a
+.IR count .
+POSIX.1\(hy2008 does not permit this behavior.
+.SS "Write Line Number"
+.P
+Historically, the
+.IR ex
+.BR =
+command, when executed in
+.IR ex
+mode in an empty edit buffer, reported 0, and from open or visual mode,
+reported 1. For consistency and simplicity of specification, POSIX.1\(hy2008 does
+not permit this behavior.
+.SS "Execute"
+.P
+Historically,
+.IR ex
+did not correctly handle the inclusion of text input commands (that is,
+.BR append ,
+.BR insert ,
+and
+.BR change )
+in executed buffers. POSIX.1\(hy2008 does not permit this exclusion for
+consistency.
+.P
+Historically, the logical contents of the buffer being executed did not
+change if the buffer itself were modified by the commands being
+executed; that is, buffer execution did not support self-modifying
+code. POSIX.1\(hy2008 requires conformance to historical practice.
+.P
+Historically, the
+.BR @
+command took a range of lines, and the
+.BR @
+buffer was executed once per line, with the current line (\c
+.BR '.' )
+set to each specified line. POSIX.1\(hy2008 requires conformance to historical
+practice.
+.P
+Some historical implementations did not notice if errors occurred
+during buffer execution. This, coupled with the ability to specify a
+range of lines for the
+.IR ex
+.BR @
+command, makes it trivial to cause them to drop
+.BR core .
+POSIX.1\(hy2008 requires that implementations stop buffer execution if any error
+occurs, if the specified line doesn't exist, or if the contents of the
+edit buffer itself are replaced (for example, the buffer executes the
+.IR ex
+.BR :edit
+command).
+.SS "Regular Expressions in ex"
+.P
+Historical practice is that the characters in the replacement part of
+the last
+.BR s
+command\(emthat is, those matched by entering a
+.BR '\(ti' 
+in the regular expression\(emwere not further expanded by the regular
+expression engine. So, if the characters contained the string
+.BR \(dqa.,\(dq 
+they would match
+.BR 'a' 
+followed by
+.BR \(dq.,\(dq 
+and not
+.BR 'a' 
+followed by any character. POSIX.1\(hy2008 requires conformance to historical
+practice.
+.SS "Edit Options in ex"
+.P
+The following paragraphs describe the historical behavior of some edit
+options that were not, for whatever reason, included in POSIX.1\(hy2008.
+Implementations are strongly encouraged to only use these names if the
+functionality described here is fully supported.
+.IP "\fBextended\fP" 10
+The
+.BR extended
+edit option has been used in some implementations of
+.IR vi
+to provide extended regular expressions instead of basic regular
+expressions This option was omitted from POSIX.1\(hy2008 because it is not
+widespread historical practice.
+.IP "\fBflash\fP" 10
+The
+.BR flash
+edit option historically caused the screen to flash instead of beeping
+on error. This option was omitted from POSIX.1\(hy2008 because it is not found in
+some historical implementations.
+.IP "\fBhardtabs\fP" 10
+The
+.BR hardtabs
+edit option historically defined the number of columns between hardware
+tab settings. This option was omitted from POSIX.1\(hy2008 because it was
+believed to no longer be generally useful.
+.IP "\fBmodeline\fP" 10
+The
+.BR modeline
+(sometimes named
+.BR modelines )
+edit option historically caused
+.IR ex
+or
+.IR vi
+to read the five first and last lines of the file for editor commands.
+This option is a security problem, and vendors are strongly encouraged
+to delete it from historical implementations.
+.IP "\fBopen\fP" 10
+The
+.BR open
+edit option historically disallowed the
+.IR ex
+.BR open
+and
+.BR visual
+commands. This edit option was omitted because these commands are
+required by POSIX.1\(hy2008.
+.IP "\fBoptimize\fP" 10
+The
+.BR optimize
+edit option historically expedited text throughput by setting the
+terminal to not do automatic
+<carriage-return>
+characters when printing more than one logical line of output. This
+option was omitted from POSIX.1\(hy2008 because it was intended for terminals
+without addressable cursors, which are rarely, if ever, still used.
+.IP "\fBruler\fP" 10
+The
+.BR ruler
+edit option has been used in some implementations of
+.IR vi
+to present a current row/column ruler for the user. This option was
+omitted from POSIX.1\(hy2008 because it is not widespread historical practice.
+.IP "\fBsourceany\fP" 10
+The
+.BR sourceany
+edit option historically caused
+.IR ex
+or
+.IR vi
+to source start-up files that were owned by users other than the user
+running the editor. This option is a security problem, and vendors are
+strongly encouraged to remove it from their implementations.
+.IP "\fBtimeout\fP" 10
+The
+.BR timeout
+edit option historically enabled the (now standard) feature of only
+waiting for a short period before returning keys that could be part of
+a macro. This feature was omitted from POSIX.1\(hy2008 because its behavior is
+now standard, it is not widely useful, and it was rarely documented.
+.IP "\fBverbose\fP" 10
+The
+.BR verbose
+edit option has been used in some implementations of
+.IR vi
+to cause
+.IR vi
+to output error messages for common errors; for example, attempting to
+move the cursor past the beginning or end of the line instead of only
+alerting the screen. (The historical
+.IR vi
+only alerted the terminal and presented no message for such errors. The
+historical editor option
+.BR terse
+did not select when to present error messages, it only made existing
+error messages more or less verbose.) This option was omitted from
+POSIX.1\(hy2008 because it is not widespread historical practice; however,
+implementors are encouraged to use it if they wish to provide error
+messages for naive users.
+.IP "\fBwraplen\fP" 10
+The
+.BR wraplen
+edit option has been used in some implementations of
+.IR vi
+to specify an automatic margin measured from the left margin instead of
+from the right margin. This is useful when multiple screen sizes are
+being used to edit a single file. This option was omitted from POSIX.1\(hy2008
+because it is not widespread historical practice; however, implementors
+are encouraged to use it if they add this functionality.
+.SS "autoindent, ai"
+.P
+Historically, the command
+.BR 0a
+did not do any autoindentation, regardless of the current indentation
+of line 1. POSIX.1\(hy2008 requires that any indentation present in line 1 be
+used.
+.SS "autoprint, ap"
+.P
+Historically, the
+.BR autoprint
+edit option was not completely consistent or based solely on
+modifications to the edit buffer. Exceptions were the
+.BR read
+command (when reading from a file, but not from a filter), the
+.BR append ,
+.BR change ,
+.BR insert ,
+.BR global ,
+and
+.BR v
+commands, all of which were not affected by
+.BR autoprint ,
+and the
+.BR tag
+command, which was affected by
+.BR autoprint .
+POSIX.1\(hy2008 requires conformance to historical practice.
+.P
+Historically, the
+.BR autoprint
+option only applied to the last of multiple commands entered using
+<vertical-line>
+delimiters; for example,
+.BR delete
+<newline>
+was affected by
+.BR autoprint ,
+but
+.BR delete|version
+<newline>
+was not. POSIX.1\(hy2008 requires conformance to historical practice.
+.SS "autowrite, aw"
+.P
+Appending the
+.BR '!' 
+character to the
+.IR ex
+.BR next
+command to avoid performing an automatic write was not supported in
+historical implementations. POSIX.1\(hy2008 requires that the behavior match the
+other
+.IR ex
+commands for consistency.
+.SS "ignorecase, ic"
+.P
+Historical implementations of case-insensitive matching (the
+.BR ignorecase
+edit option) lead to counter-intuitive situations when uppercase
+characters were used in range expressions. Historically, the process
+was as follows:
+.IP " 1." 4
+Take a line of text from the edit buffer.
+.IP " 2." 4
+Convert uppercase to lowercase in text line.
+.IP " 3." 4
+Convert uppercase to lowercase in regular expressions, except in
+character class specifications.
+.IP " 4." 4
+Match regular expressions against text.
+.P
+This would mean that, with
+.BR ignorecase
+in effect, the text:
+.sp
+.RS 4
+.nf
+
+The cat sat on the mat
+.fi
+.P
+.RE
+.P
+would be matched by
+.sp
+.RS 4
+.nf
+
+/\(hathe/
+.fi
+.P
+.RE
+.P
+but not by:
+.sp
+.RS 4
+.nf
+
+/\(ha[A-Z]he/
+.fi
+.P
+.RE
+.P
+For consistency with other commands implementing regular expressions,
+POSIX.1\(hy2008 does not permit this behavior.
+.SS "paragraphs, para"
+.P
+The ISO\ POSIX\(hy2:\|1993 standard made the default
+.BR paragraphs
+and
+.BR sections
+edit options implementation-defined, arguing they were historically
+oriented to the UNIX system
+.IR troff
+text formatter, and a ``portable user'' could use the
+.BR { ,
+.BR } ,
+.BR [[ ,
+.BR ]] ,
+.BR ( ,
+and
+.BR )
+commands in open or visual mode and have the cursor stop in unexpected
+places. POSIX.1\(hy2008 specifies their values in the POSIX locale because the
+unusual grouping (they only work when grouped into two characters at a
+time) means that they cannot be used for general-purpose movement,
+regardless.
+.SS "readonly"
+.P
+Implementations are encouraged to provide the best possible information
+to the user as to the read-only status of the file, with the exception
+that they should not consider the current special privileges of the
+process. This provides users with a safety net because they must force
+the overwrite of read-only files, even when running with additional
+privileges.
+.P
+The
+.BR readonly
+edit option specification largely conforms to historical practice. The
+only difference is that historical implementations did not notice that
+the user had set the
+.BR readonly
+edit option in cases where the file was already marked read-only for
+some reason, and would therefore reinitialize the
+.BR readonly
+edit option the next time the contents of the edit buffer were
+replaced. This behavior is disallowed by POSIX.1\(hy2008.
+.SS "report"
+.P
+The requirement that lines copied to a buffer interact differently than
+deleted lines is historical practice. For example, if the
+.BR report
+edit option is set to 3, deleting 3 lines will cause a report to be
+written, but 4 lines must be copied before a report is written.
+.P
+The requirement that the
+.IR ex
+.BR global ,
+.BR v ,
+.BR open ,
+.BR undo ,
+and
+.BR visual
+commands present reports based on the total number of lines added or
+deleted during the command execution, and that commands executed by the
+.BR global
+and
+.BR v
+commands not present reports, is historical practice. POSIX.1\(hy2008 extends
+historical practice by requiring that buffer execution be treated
+similarly. The reasons for this are two-fold. Historically, only the
+report by the last command executed from the buffer would be seen by
+the user, as each new report would overwrite the last. In addition, the
+standard developers believed that buffer execution had more in common
+with
+.BR global
+and
+.BR v
+commands than it did with other
+.IR ex
+commands, and should behave similarly, for consistency and simplicity
+of specification.
+.SS "showmatch, sm"
+.P
+The length of time the cursor spends on the matching character is
+unspecified because the timing capabilities of systems are often
+inexact and variable. The time should be long enough for the user to
+notice, but not long enough for the user to become annoyed. Some
+implementations of
+.IR vi
+have added a
+.BR matchtime
+option that permits users to set the number of 0,1 second intervals the
+cursor pauses on the matching character.
+.SS "showmode"
+.P
+The
+.BR showmode
+option has been used in some historical implementations of
+.IR ex
+and
+.IR vi
+to display the current editing mode when in open or visual mode. The
+editing modes have generally included ``command'' and ``input'', and
+sometimes other modes such as ``replace'' and ``change''. The string
+was usually displayed on the bottom line of the screen at the far
+right-hand corner. In addition, a preceding
+.BR '*' 
+character often denoted whether the contents of the edit buffer had
+been modified. The latter display has sometimes been part of the
+.BR showmode
+option, and sometimes based on another option. This option was not
+available in the 4 BSD historical implementation of
+.IR vi ,
+but was viewed as generally useful, particularly to novice users, and
+is required by POSIX.1\(hy2008.
+.P
+The
+.BR smd
+shorthand for the
+.BR showmode
+option was not present in all historical implementations of the editor.
+POSIX.1\(hy2008 requires it, for consistency.
+.P
+Not all historical implementations of the editor displayed a mode
+string for command mode, differentiating command mode from text input
+mode by the absence of a mode string. POSIX.1\(hy2008 permits this behavior for
+consistency with historical practice, but implementations are
+encouraged to provide a display string for both modes.
+.SS "slowopen"
+.P
+Historically, the
+.BR slowopen
+option was automatically set if the terminal baud rate was less than
+1\|200 baud, or if the baud rate was 1\|200 baud and the
+.BR redraw
+option was not set. The
+.BR slowopen
+option had two effects. First, when inserting characters in the middle
+of a line, characters after the cursor would not be pushed ahead, but
+would appear to be overwritten. Second, when creating a new line of
+text, lines after the current line would not be scrolled down, but
+would appear to be overwritten. In both cases, ending text input mode
+would cause the screen to be refreshed to match the actual contents of
+the edit buffer. Finally, terminals that were sufficiently intelligent
+caused the editor to ignore the
+.BR slowopen
+option. POSIX.1\(hy2008 permits most historical behavior, extending historical
+practice to require
+.BR slowopen
+behaviors if the edit option is set by the user.
+.SS "tags"
+.P
+The default path for tags files is left unspecified as implementations
+may have their own
+.BR tags
+implementations that do not correspond to the historical ones. The
+default
+.BR tags
+option value should probably at least include the file
+.BR ./tags .
+.SS "term"
+.P
+Historical implementations of
+.IR ex
+and
+.IR vi
+ignored changes to the
+.BR term
+edit option after the initial terminal information was loaded. This is
+permitted by POSIX.1\(hy2008; however, implementations are encouraged to permit
+the user to modify their terminal type at any time.
+.SS "terse"
+.P
+Historically, the
+.BR terse
+edit option optionally provided a shorter, less descriptive error
+message, for some error messages. This is permitted, but not required,
+by POSIX.1\(hy2008. Historically, most common visual mode errors (for example,
+trying to move the cursor past the end of a line) did not result in an
+error message, but simply alerted the terminal. Implementations wishing
+to provide messages for novice users are urged to do so based on the
+.BR edit
+option
+.BR verbose ,
+and not
+.BR terse .
+.SS "window"
+.P
+In historical implementations, the default for the
+.BR window
+edit option was based on the baud rate as follows:
+.IP " 1." 4
+If the baud rate was less than 1\|200, the
+.BR edit
+option
+.BR w300
+set the window value; for example, the line:
+.RS 4 
+.sp
+.RS 4
+.nf
+
+set w300=12
+.fi
+.P
+.RE
+.P
+would set the window option to 12 if the baud rate was less than
+1\|200.
+.RE
+.IP " 2." 4
+If the baud rate was equal to 1\|200, the
+.BR edit
+option
+.BR w1200
+set the window value.
+.IP " 3." 4
+If the baud rate was greater than 1\|200, the
+.BR edit
+option
+.BR w9600
+set the window value.
+.P
+The
+.BR w300 ,
+.BR w1200 ,
+and
+.BR w9600
+options do not appear in POSIX.1\(hy2008 because of their dependence on specific
+baud rates.
+.P
+In historical implementations, the size of the window displayed by
+various commands was related to, but not necessarily the same as, the
+.BR window
+edit option. For example, the size of the window was set by the
+.IR ex
+command
+.BR "visual 10" ,
+but it did not change the value of the
+.BR window
+edit option. However, changing the value of the
+.BR window
+edit option did change the number of lines that were displayed when the
+screen was repainted. POSIX.1\(hy2008 does not permit this behavior in the
+interests of consistency and simplicity of specification, and requires
+that all commands that change the number of lines that are displayed do
+it by setting the value of the
+.BR window
+edit option.
+.SS "wrapmargin, wm"
+.P
+Historically, the
+.BR wrapmargin
+option did not affect maps inserting characters that also had
+associated
+.IR count s;
+for example
+.BR ":map\0K\05aABC\0DEF" .
+Unfortunately, there are widely used maps that depend on this behavior.
+For consistency and simplicity of specification, POSIX.1\(hy2008 does not permit
+this behavior.
+.P
+Historically,
+.BR wrapmargin
+was calculated using the column display width of all characters on the
+screen. For example, an implementation using
+.BR \(dq\(haI\(dq 
+to represent
+<tab>
+characters when the
+.BR list
+edit option was set, where
+.BR '\(ha' 
+and
+.BR 'I' 
+each took up a single column on the screen, would calculate the
+.BR wrapmargin
+based on a value of 2 for each
+<tab>.
+The
+.BR number
+edit option similarly changed the effective length of the line as well.
+POSIX.1\(hy2008 requires conformance to historical practice.
+.P
+Earlier versions of this standard allowed for implementations
+with bytes other than eight bits, but this has been modified in this
+version.
+.SH "FUTURE DIRECTIONS"
+None.
+.SH "SEE ALSO"
+.IR "Section 2.9.1.1" ", " "Command Search and Execution",
+.IR "\fIctags\fR\^",
+.IR "\fIed\fR\^",
+.IR "\fIsed\fR\^",
+.IR "\fIsh\fR\^",
+.IR "\fIstty\fR\^",
+.IR "\fIvi\fR\^"
+.P
+The Base Definitions volume of POSIX.1\(hy2017,
+.IR "Table 5-1" ", " "Escape Sequences and Associated Actions",
+.IR "Chapter 8" ", " "Environment Variables",
+.IR "Section 9.3" ", " "Basic Regular Expressions",
+.IR "Section 12.2" ", " "Utility Syntax Guidelines"
+.P
+The System Interfaces volume of POSIX.1\(hy2017,
+.IR "\fIaccess\fR\^(\|)"
+.\"
+.SH COPYRIGHT
+Portions of this text are reprinted and reproduced in electronic form
+from IEEE Std 1003.1-2017, Standard for Information Technology
+-- Portable Operating System Interface (POSIX), The Open Group Base
+Specifications Issue 7, 2018 Edition,
+Copyright (C) 2018 by the Institute of
+Electrical and Electronics Engineers, Inc and The Open Group.
+In the event of any discrepancy between this version and the original IEEE and
+The Open Group Standard, the original IEEE and The Open Group Standard
+is the referee document. The original Standard can be obtained online at
+http://www.opengroup.org/unix/online.html .
+.PP
+Any typographical or formatting errors that appear
+in this page are most likely
+to have been introduced during the conversion of the source files to
+man page format. To report such errors, see
+https://www.kernel.org/doc/man-pages/reporting_bugs.html .