path: root/man/man1/man.man1

'\" t
.\" ** The above line should force tbl to be a preprocessor **
.\" Man page for man
.\"
.\" Copyright (C) 1994, 1995, Graeme W. Wilford. (Wilf.)
.\" Copyright (C) 2001-2019 Colin Watson.
.\"
.\" You may distribute under the terms of the GNU General Public
.\" License as specified in the file docs/COPYING.GPLv2 that comes with the
.\" man-db distribution.
.\"
.\" Sat Oct 29 13:09:31 GMT 1994  Wilf. (G.Wilford@ee.surrey.ac.uk)
.\"
.pc
.TH %thman% 1 "%date%" "%version%" "Manual pager utils"
.SH NAME
%man% \- an interface to the system reference manuals
.SH SYNOPSIS
.\" The general command line
.B %man%
.RI [\| "man options" \|]
.RI [\|[\| section \|]
.IR page \ \|.\|.\|.\|]\ \.\|.\|.\&
.\" The apropos command line
.br
.B %man%
.B \-k
.RI [\| "apropos options" \|]
.I regexp
\&.\|.\|.\&
.\" The --global-apropos command line
.br
.B %man%
.B \-K
.RI [\| "man options" \|]
.RI [\| section \|]
.IR term \ .\|.\|.\&
.\" The whatis command line
.br
.B %man%
.B \-f
.RI [\| whatis
.IR options \|]
.I page
\&.\|.\|.\&
.\" The --local command line
.br
.B %man%
.B \-l
.RI [\| "man options" \|]
.I file
\&.\|.\|.\&
.\" The --where/--where-cat command line
.br
.B %man%
.BR \-w \||\| \-W
.RI [\| "man options" \|]
.I page
\&.\|.\|.\&
.SH DESCRIPTION
.B %man%
is the system's manual pager.
Each
.I page
argument given to
.B %man%
is normally the name of a program, utility or function.
The
.I manual page
associated with each of these arguments is then found and displayed.
A
.IR section ,
if provided, will direct
.B %man%
to look only in that
.I section
of the manual.
The default action is to search in all of the available
.I sections
following a pre-defined order (see
.BR DEFAULTS ),
and to show only the first
.I page
found, even if
.I page
exists in several
.IR sections .

The table below shows the
.I section
numbers of the manual followed by the types of pages they contain.

.TS
tab (@);
l lx.
1@T{
Executable programs or shell commands
T}
2@T{
System calls (functions provided by the kernel)
T}
3@T{
Library calls (functions within program libraries)
T}
4@T{
Special files (usually found in \fI/dev\/\fR)
T}
5@T{
File formats and conventions, e.g.\& \fI/etc/passwd\fR
T}
6@T{
Games
T}
7@T{
Miscellaneous (including macro packages and conventions),
e.g.\& \fBman\fR(7), \fBgroff\fR(7), \fBman\-pages\fR(7)
T}
8@T{
System administration commands (usually only for root)
T}
9@T{
Kernel routines [\|Non standard\|]
T}
.TE

A manual
.I page
consists of several sections.

Conventional section names include
.BR NAME ,
.BR SYNOPSIS ,
.BR CONFIGURATION ,
.BR DESCRIPTION ,
.BR OPTIONS ,
.BR EXIT\ STATUS ,
.BR RETURN\ VALUE ,
.BR ERRORS ,
.BR ENVIRONMENT ,
.BR FILES ,
.BR VERSIONS ,
.BR STANDARDS ,
.BR NOTES ,
.BR BUGS ,
.BR EXAMPLE ,
.BR AUTHORS ,
and
.BR SEE\ ALSO .

The following conventions apply to the
.B SYNOPSIS
section and can be used as a guide in other sections.

.TS
tab (@);
l lx.
\fBbold text\fR@T{
type exactly as shown.
T}
\fIitalic text\fR@T{
replace with appropriate argument.
T}
[\|\fB\-abc\fR\|]@T{
any or all arguments within [ ] are optional.
T}
\fB\-a\|\fR|\|\fB\-b\fR@T{
options delimited by | cannot be used together.
T}
\fIargument\fR .\|.\|.@T{
\fIargument\fR is repeatable.
T}
[\|\fIexpression\fR\|]\fR .\|.\|.@T{
\fRentire \fIexpression\fR\ within [ ] is repeatable.
T}
.TE

Exact rendering may vary depending on the output device.
For instance, man will usually not be able to render italics when running in
a terminal, and will typically use underlined or coloured text instead.

The command or function illustration is a pattern that should match all
possible invocations.
In some cases it is advisable to illustrate several exclusive invocations
as is shown in the
.B SYNOPSIS
section of this manual page.
.SH EXAMPLES
.TP \w'%man%\ 'u
.BI %man% \ ls
Display the manual page for the
.I item
(program)
.IR ls .
.TP
\fB%man%\fR \fIman\fR.\fI7\fR
Display the manual page for macro package
.I man
from section
.IR 7 .
(This is an alternative spelling of
"\fB%man%\fR \fI7 man\fR".)
.TP
\fB%man% '\fIman\fR(\fI7\fR)'
Display the manual page for macro package
.I man
from section
.IR 7 .
(This is another alternative spelling of
"\fB%man%\fR \fI7 man\fR".
It may be more convenient when copying and pasting cross-references to
manual pages.
Note that the parentheses must normally be quoted to protect them from the
shell.)
.TP
.BI %man%\ \-a \ intro
Display, in succession, all of the available
.I intro
manual pages contained within the manual.
It is possible to quit between successive displays or skip any of them.
.TP
\fB%man% \-t \fIbash \fR|\fI lpr \-Pps
Format the manual page for
.I bash
into the default
.B troff
or
.B groff
format and pipe it to the printer named
.IR ps .
The default output for
.B groff
is usually PostScript.
.B %man% \-\-help
should advise as to which processor is bound to the
.B \-t
option.
.TP
.BI "%man% \-l \-T" "dvi ./foo.1x.gz" " > " ./foo.1x.dvi
This command will decompress and format the nroff source manual page
.I ./foo.1x.gz
into a
.B device independent (dvi)
file.
The redirection is necessary as the
.B \-T
flag causes output to be directed to
.B stdout
with no pager.
The output could be viewed with a program such as
.B xdvi
or further processed into PostScript using a program such as
.BR dvips .
.TP
.BI %man%\ \-k \ printf
Search the short descriptions and manual page names for the keyword
.I printf
as regular expression.
Print out any matches.
Equivalent to
.BI %apropos% \ printf .
.TP
.BI %man%\ \-f \ smail
Lookup the manual pages referenced by
.I smail
and print out the short descriptions of any found.
Equivalent to
.BI %whatis% \ smail .
.SH OVERVIEW
Many options are available to
.B %man%
in order to give as much flexibility as possible to the user.
Changes can be made to the search path, section order, output processor,
and other behaviours and operations detailed below.

If set, various environment variables are interrogated to determine
the operation of
.BR %man% .
It is possible to set the "catch-all" variable
.RB $ MANOPT
to any string in command line format, with the exception that any spaces
used as part of an option's argument must be escaped (preceded by a
backslash).
.B %man%
will parse
.RB $ MANOPT
prior to parsing its own command line.
Those options requiring an argument will be overridden by the same options
found on the command line.
To reset all of the options set in
.RB $ MANOPT ,
.B \-D
can be specified as the initial command line option.
This will allow %man% to "forget" about the options specified in
.RB $ MANOPT ,
although they must still have been valid.

Manual pages are normally stored in
.BR nroff (1)
format under a directory such as
.IR /usr/share/man .
In some installations, there may also be preformatted
.I cat pages
to improve performance.
See
.BR manpath (5)
for details of where these files are stored.

This package supports manual pages in multiple languages, controlled by your
.IR locale .
If your system did not set this up for you automatically, then you may need
to set
.RB $ LC_MESSAGES ,
.RB $ LANG ,
or another system-dependent environment variable to indicate your preferred
locale, usually specified in the
.B POSIX
format:

<\fIlanguage\fR>\
[\|\fB_\fR<\fIterritory\fR>\|\
[\|\fB.\fR<\fIcharacter-set\fR>\|\
[\|\fB,\fR<\fIversion\fR>\|]\|]\|]

If the desired page is available in your
.IR locale ,
it will be displayed in lieu of the standard
(usually American English) page.

If you find that the translations supplied with this package are not
available in your native language and you would like to supply them, please
contact the maintainer who will be coordinating such activity.

Individual manual pages are normally written and maintained by the
maintainers of the program, function, or other topic that they document, and
are not included with this package.
If you find that a manual page is missing or inadequate, please report that
to the maintainers of the package in question.

For information regarding other features and extensions available with this
manual pager, please read the documents supplied with the package.
.SH DEFAULTS
The order of sections to search may be overridden by the environment
variable
.RB $ MANSECT
or by the
.B SECTION
directive in
.IR %manpath_config_file% .
By default it is as follows:

.RS
.if !'po4a'hide' %sections%
.RE

The formatted manual page is displayed using a
.IR pager .
This can be specified in a number of ways, or else will fall back to a
default (see option
.B \-P
for details).

The filters are deciphered by a number of means.
Firstly, the command line option
.B \-p
or the environment variable
.RB $ MANROFFSEQ
is interrogated.
If
.B \-p
was not used and the environment variable was not set, the initial line of
the nroff file is parsed for a preprocessor string.
To contain a valid preprocessor string, the first line must resemble

.B '\e"
.RB < string >

where
.B string
can be any combination of letters described by option
.B \-p
below.

If none of the above methods provide any filter information, a default set
is used.

A formatting pipeline is formed from the filters and the primary
formatter
.RB ( nroff
or
.RB [ tg ] roff
with
.BR \-t )
and executed.
Alternatively, if an executable program
.I mandb_nfmt
(or
.I mandb_tfmt
with
.BR \-t )
exists in the man tree root, it is executed instead.
It gets passed the manual source file, the preprocessor string, and
optionally the device specified with
.BR \-T " or " \-E
as arguments.
.\" ********************************************************************
.SH OPTIONS
Non-argument options that are duplicated either on the command line, in
.RB $ MANOPT ,
or both, are not harmful.
For options that require an argument, each duplication will override the
previous argument value.
.SS "General options"
.TP
.BI \-C\  file \fR,\ \fB\-\-config\-file= file
Use this user configuration file rather than the default of
.IR \(ti/.manpath .
.TP
.if !'po4a'hide' .BR \-d ", " \-\-debug
Print debugging information.
.TP
.if !'po4a'hide' .BR \-D ", " \-\-default
This option is normally issued as the very first option and resets
.B %man%'s
behaviour to its default.
Its use is to reset those options that may have been set in
.RB $ MANOPT .
Any options that follow
.B \-D
will have their usual effect.
.TP
\fB\-\-warnings\fP[=\fIwarnings\/\fP]
Enable warnings from
.IR groff .
This may be used to perform sanity checks on the source text of manual
pages.
.I warnings
is a comma-separated list of warning names; if it is not supplied, the
default is "mac".
To disable a
.I groff
warning, prefix it with "!": for example,
.B \-\-warnings=mac,!break
enables warnings in the "mac" category and disables warnings in the "break"
category.
See the \(lqWarnings\(rq node in
.B info groff
for a list of available warning names.
.SS "Main modes of operation"
.TP
.if !'po4a'hide' .BR \-f ", " \-\-whatis
Approximately equivalent to
.BR %whatis% .
Display a short description from the manual page, if available.
See
.BR %whatis% (1)
for details.
.TP
.if !'po4a'hide' .BR \-k ", " \-\-apropos
Approximately equivalent to
.BR %apropos% .
Search the short manual page descriptions for keywords and display any
matches.
See
.BR %apropos% (1)
for details.
.TP
.if !'po4a'hide' .BR \-K ", " \-\-global\-apropos
Search for text in all manual pages.
This is a brute-force search, and is likely to take some time; if you can,
you should specify a section to reduce the number of pages that need to be
searched.
Search terms may be simple strings (the default), or regular expressions if
the
.B \-\-regex
option is used.
.IP
Note that this searches the
.I sources
of the manual pages, not the rendered text, and so may include false
positives due to things like comments in source files, or false negatives
due to things like hyphens being written as "\e-" in source files.
Searching the rendered text would be much slower.
.TP
.if !'po4a'hide' .BR \-l ", " \-\-local\-file
Activate "local" mode.
Format and display local manual files instead of searching through the
system's manual collection.
Each manual page argument will be interpreted as an nroff source file in the
correct format.
.\" Compressed nroff source files with a supported compression
.\" extension will be decompressed by man prior to being displaying via the
.\" usual filters.
No cat file is produced.
If '\-' is listed as one of the arguments, input will be taken from stdin.
.IP
If this option is not used, then
.B %man%
will also fall back to interpreting manual page arguments as local file
names if the argument contains a "/" character, since that is a good
indication that the argument refers to a path on the file system.
.TP
.if !'po4a'hide' .BR \-w ", " \-\-where ", " \-\-path ", " \-\-location
Don't actually display the manual page, but do print the location of the
source nroff file that would be formatted.
If the
.B \-a
option is also used, then print the locations of all source files that match
the search criteria.
.TP
.if !'po4a'hide' .BR \-W ", " \-\-where\-cat ", " \-\-location\-cat
Don't actually display the manual page, but do print the location of the
preformatted cat file that would be displayed.
If the
.B \-a
option is also used, then print the locations of all preformatted cat files
that match the search criteria.
.IP
If
.B \-w
and
.B \-W
are both used, then print both source file and cat file separated by a
space.
If
all of
.BR \-w ,
.BR \-W ,
and
.B \-a
are used, then do this for each possible match.
.TP
.if !'po4a'hide' .BR \-c ", " \-\-catman
This option is not for general use and should only be used by the
.B %catman%
program.
.TP
.BI \-R\  encoding\fR,\ \fI \-\-recode\fR=\fIencoding
Instead of formatting the manual page in the usual way, output its source
converted to the specified
.IR encoding .
If you already know the encoding of the source file, you can also use
.BR %manconv% (1)
directly.
However, this option allows you to convert several manual pages to a single
encoding without having to explicitly state the encoding of each, provided
that they were already installed in a structure similar to a manual page
hierarchy.
.IP
Consider using
.BR %man_recode% (1)
instead for converting multiple manual pages, since it has an interface
designed for bulk conversion and so can be much faster.
.SS "Finding manual pages"
.TP
.BI \-L\  locale \fR,\ \fB\-\-locale= locale
.B %program%
will normally determine your current locale by a call to the C function
.BR setlocale (3)
which interrogates various environment variables, possibly including
.RB $ LC_MESSAGES
and
.RB $ LANG .
To temporarily override the determined value, use this option to supply a
.I locale
string directly to
.BR %program% .
Note that it will not take effect until the search for pages actually
begins.
Output such as the help message will always be displayed in the initially
determined locale.
.TP
\fB\-m\fR \fIsystem\fR\|[\|,.\|.\|.\|]\|, \
\fB\-\-systems=\fIsystem\fR\|[\|,.\|.\|.\|]
If this system has access to other operating systems' manual pages, they can
be accessed using this option.
To search for a manual page from NewOS's manual page collection,
use the option
.B \-m
.BR NewOS .

The
.I system
specified can be a combination of comma delimited operating system names.
To include a search of the native operating system's manual pages,
include the system name
.B man
in the argument string.
This option will override the
.RB $ SYSTEM
environment variable.
.TP
.BI \-M\  path \fR,\ \fB\-\-manpath= path
Specify an alternate manpath to use.
By default,
.B %man%
uses
.B %manpath%
derived code to determine the path to search.
This option overrides the
.RB $ MANPATH
environment variable and causes option
.B \-m
to be ignored.

A path specified as a manpath must be the root of a manual page hierarchy
structured into sections as described in the man-db manual (under "The
manual page system").
To view manual pages outside such hierarchies, see the
.B \-l
option.
.TP
\fB\-S\fR \fIlist\/\fR, \
\fB\-s\fR \fIlist\/\fR, \
\fB\-\-sections=\fIlist\/\fR
The given
.I list
is a colon- or comma-separated list of sections, used to determine which
manual sections to search and in what order.
This option overrides the
.RB $ MANSECT
environment variable.
(The
.B \-s
spelling is for compatibility with System V.)
.TP
.BI \-e\  sub-extension \fR,\ \fB\-\-extension= sub-extension
Some systems incorporate large packages of manual pages, such as those that
accompany the
.B Tcl
package, into the main manual page hierarchy.
To get around the problem of having two manual pages with the same name
such as
.BR exit (3),
the
.B Tcl
pages were usually all assigned to section
.BR l .
As this is unfortunate, it is now possible to put the pages in the correct
section, and to assign a specific "extension" to them, in this case,
.BR exit (3tcl).
Under normal operation,
.B %man%
will display
.BR exit (3)
in preference to
.BR exit (3tcl).
To negotiate this situation and to avoid having to know which section the
page you require resides in, it is now possible to give
.B %man%
a
.I sub-extension
string indicating which package the page must belong to.
Using the above example, supplying the option
.B \-e\ tcl
to
.B %man%
will restrict the search to pages having an extension of
.BR *tcl .
.TP
.if !'po4a'hide' .BR \-i ", " \-\-ignore\-case
Ignore case when searching for manual pages.
This is the default.
.TP
.if !'po4a'hide' .BR \-I ", " \-\-match\-case
Search for manual pages case-sensitively.
.TP
.if !'po4a'hide' .B \-\-regex
Show all pages with any part of either their names or their descriptions
matching each
.I page
argument as a regular expression, as with
.BR apropos (1).
Since there is usually no reasonable way to pick a "best" page when
searching for a regular expression, this option implies
.BR \-a .
.TP
.if !'po4a'hide' .B \-\-wildcard
Show all pages with any part of either their names or their descriptions
matching each
.I page
argument using shell-style wildcards, as with
.BR apropos (1)
.BR \-\-wildcard .
The
.I page
argument must match the entire name or description, or match on word
boundaries in the description.
Since there is usually no reasonable way to pick a "best" page when
searching for a wildcard, this option implies
.BR \-a .
.TP
.if !'po4a'hide' .B \-\-names\-only
If the
.B \-\-regex
or
.B \-\-wildcard
option is used, match only page names, not page descriptions, as with
.BR whatis (1).
Otherwise, no effect.
.TP
.if !'po4a'hide' .BR \-a ", " \-\-all
By default,
.B %man%
will exit after displaying the most suitable manual page it finds.
Using this option forces
.B %man%
to display all the manual pages with names that match the search criteria.
.TP
.if !'po4a'hide' .BR \-u ", " \-\-update
This option causes
.B %man%
to update its database caches of installed manual pages.
This is only needed in rare situations, and it is normally better to run
.BR %mandb% (8)
instead.
.TP
.if !'po4a'hide' .B \-\-no\-subpages
By default,
.B %man%
will try to interpret pairs of manual page names given on the command line
as equivalent to a single manual page name containing a hyphen or an
underscore.
This supports the common pattern of programs that implement a number of
subcommands, allowing them to provide manual pages for each that can be
accessed using similar syntax as would be used to invoke the subcommands
themselves.
For example:

.nf
.if !'po4a'hide' \&  $ man \-aw git diff
.if !'po4a'hide' \&  /usr/share/man/man1/git\-diff.1.gz
.fi

To disable this behaviour, use the
.B \-\-no\-subpages
option.

.nf
.if !'po4a'hide' \&  $ man \-aw \-\-no\-subpages git diff
.if !'po4a'hide' \&  /usr/share/man/man1/git.1.gz
.if !'po4a'hide' \&  /usr/share/man/man3/Git.3pm.gz
.if !'po4a'hide' \&  /usr/share/man/man1/diff.1.gz
.fi
.SS "Controlling formatted output"
.TP
.BI \-P\  pager \fR,\ \fB\-\-pager= pager
Specify which output pager to use.
By default,
.B %man%
uses
.BR "%pager%" ,
falling back to
.B %cat%
if
.B %pager%
is not found or is not executable.
This option overrides the
.RB $ MANPAGER
environment variable, which in turn overrides the
.RB $ PAGER
environment variable.
It is not used in conjunction with
.B \-f
or
.BR \-k .

The value may be a simple command name or a command with arguments, and may
use shell quoting (backslashes, single quotes, or double quotes).
It may not use pipes to connect multiple commands; if you need that, use a
wrapper script, which may take the file to display either as an argument or
on standard input.
.TP
.BI \-r\  prompt \fR,\ \fB\-\-prompt= prompt
If a recent version of
.B less
is used as the pager,
.B %man%
will attempt to set its prompt and some sensible options.
The default prompt looks like

.BI " Manual page" " name" ( sec ") line" " x"

where
.I name
denotes the manual page name,
.I sec
denotes the section it was found under and
.I x
the current line number.
.\"The default options are
.\".BR \-six8 .
This is achieved by using the
.RB $ LESS
environment variable.
.\"The actual default will depend on your chosen
.\".BR locale .

Supplying
.B \-r
with a string will override this default.
.\"You may need to do this if your
.\"version of
.\".B less
.\"rejects the default options or if you prefer a different prompt.
The string may contain the text
.B $MAN_PN
which will be expanded to the name of the current manual page and its
section name surrounded by "(" and ")".
The string used to produce the default could be expressed as

.B \e\ Manual\e\ page\e\ \e$MAN_PN\e\ ?ltline\e\ %lt?L/%L.:
.br
.B byte\e\ %bB?s/%s..?\e\ (END):?pB\e\ %pB\e\e%..
.br
.B (press h for help or q to quit)

It is broken into three lines here for the sake of readability only.
For its meaning see the
.BR less (1)
manual page.
The prompt string is first evaluated by the shell.
All double quotes, back-quotes and backslashes in the prompt must be escaped
by a preceding backslash.
The prompt string may end in an escaped $ which may be followed by further
options for less.
By default
.B %man%
sets the
.B \-ix8
options.

The
.RB $ MANLESS
environment variable described below may be used to set a default prompt
string if none is supplied on the command line.
.TP
.if !'po4a'hide' .BR \-7 ", " \-\-ascii
When viewing a pure
.IR ascii (7)
manual page on a 7 bit terminal or terminal emulator, some characters may
not display correctly when using the
.IR latin1 (7)
device description with
.B GNU
.BR nroff .
This option allows pure
.I ascii
manual pages to be displayed in
.I ascii
with the
.I latin1
device.
It will not translate any
.I latin1
text.
The following table shows the translations performed: some parts of it may
only be displayed properly when using
.B GNU
.BR nroff 's
.IR latin1 (7)
device.

.ie c \[shc] \
.  ds softhyphen \[shc]
.el \
.  ds softhyphen \(hy
.na
.TS
tab (@);
l c c c.
Description@Octal@latin1@ascii
_
T{
continuation hyphen
T}@255@\*[softhyphen]@-
T{
bullet (middle dot)
T}@267@\(bu@o
T{
acute accent
T}@264@\(aa@'
T{
multiplication sign
T}@327@\(mu@x
.TE
.ad

If the
.I latin1
column displays correctly, your terminal may be set up for
.I latin1
characters and this option is not necessary.
If the
.I latin1
and
.I ascii
columns are identical, you are reading this page using this option or
.B %man%
did not format this page using the
.I latin1
device description.
If the
.I latin1
column is missing or corrupt, you may need to view manual pages with this
option.

This option is ignored when using options
.BR \-t ,
.BR \-H ,
.BR \-T ,
or
.B \-Z
and may be useless for
.B nroff
other than
.BR GNU's .
.TP
.BI \-E\  encoding\fR,\ \fI \-\-encoding\fR=\fIencoding
Generate output for a character encoding other than the default.
For backward compatibility,
.I encoding
may be an
.B nroff
device such as
.BR ascii ", " latin1 ", or " utf8
as well as a true character encoding such as
.BR UTF\-8 .
.TP
.if !'po4a'hide' .BR \-\-no\-hyphenation ", " \-\-nh
Normally,
.B nroff
will automatically hyphenate text at line breaks even in words that do not
contain hyphens, if it is necessary to do so to lay out words on a line
without excessive spacing.
This option disables automatic hyphenation, so words will only be hyphenated
if they already contain hyphens.

If you are writing a manual page and simply want to prevent
.B nroff
from hyphenating a word at an inappropriate point, do not use this option,
but consult the
.B nroff
documentation instead; for instance, you can put "\e%" inside a word to
indicate that it may be hyphenated at that point, or put "\e%" at the start
of a word to prevent it from being hyphenated.
.TP
.if !'po4a'hide' .BR \-\-no\-justification ", " \-\-nj
Normally,
.B nroff
will automatically justify text to both margins.
This option disables full justification, leaving justified only to the left
margin, sometimes called "ragged-right" text.

If you are writing a manual page and simply want to prevent
.B nroff
from justifying certain paragraphs, do not use this option, but consult the
.B nroff
documentation instead; for instance, you can use the ".na", ".nf", ".fi",
and ".ad" requests to temporarily disable adjusting and filling.
.TP
.BI \-p\  string \fR,\ \fB\-\-preprocessor= string
Specify the sequence of preprocessors to run before
.B nroff
or
.BR troff / groff .
Not all installations will have a full set of preprocessors.
Some of the preprocessors and the letters used to designate them are:
.BR eqn " (" e ),
.BR grap " (" g ),
.BR pic " (" p ),
.BR tbl " (" t ),
.BR vgrind " (" v ),
.BR refer " (" r ).
This option overrides the
.RB $ MANROFFSEQ
environment variable.
.B %zsoelim%
is always run as the very first preprocessor.
.TP
.if !'po4a'hide' .BR \-t ", " \-\-troff
Use
.I %troff%
to format the manual page to stdout.
This option is not required in conjunction with
.BR \-H ,
.BR \-T ,
or
.BR \-Z .
.TP
\fB\-T\fP[\fIdevice\/\fP], \fB\-\-troff\-device\fP[=\fIdevice\/\fP]
This option is used to change
.B groff
(or possibly
.BR troff's )
output to be suitable for a device other than the default.
It implies
.BR \-t .
Examples (as of groff 1.23.0) include
.BR dvi ,
.BR latin1 ,
.BR pdf ,
.BR ps ,
.BR utf8 ,
.BR X75
and
.BR X100 .
.TP
\fB\-H\fP[\fIbrowser\/\fP], \fB\-\-html\fP[=\fIbrowser\/\fP]
This option will cause
.B groff
to produce HTML output, and will display that output in a web browser.
The choice of browser is determined by the optional
.I browser
argument if one is provided, by the
.RB $ BROWSER
environment variable, or by a compile-time default if that is unset (usually
.BR lynx ).
This option implies
.BR \-t ,
and will only work with
.B GNU
.BR troff .
.TP
\fB\-X\fP[\fIdpi\/\fP], \fB\-\-gxditview\fP[=\fIdpi\/\fP]
This option displays the output of
.B groff
in a graphical window using the
.B gxditview
program.
The
.I dpi
(dots per inch) may be 75, 75-12, 100, or 100-12, defaulting to 75;
the -12 variants use a 12-point base font.
This option implies
.B \-T
with the X75, X75-12, X100, or X100-12 device respectively.
.TP
.if !'po4a'hide' .BR \-Z ", " \-\-ditroff
.B groff
will run
.B troff
and then use an appropriate post-processor to produce output suitable for
the chosen device.
If
.I %troff%
is
.BR groff ,
this option is passed to
.B groff
and will suppress the use of a post-processor.
It implies
.BR \-t .
.SS "Getting help"
.TP
.if !'po4a'hide' .BR \-? ", " \-\-help
Print a help message and exit.
.TP
.if !'po4a'hide' .B \-\-usage
Print a short usage message and exit.
.TP
.if !'po4a'hide' .BR \-V ", " \-\-version
Display version information.
.SH "EXIT STATUS"
.TP
.if !'po4a'hide' .B 0
Successful program execution.
.TP
.if !'po4a'hide' .B 1
Usage, syntax or configuration file error.
.TP
.if !'po4a'hide' .B 2
Operational error.
.TP
.if !'po4a'hide' .B 3
A child process returned a non-zero exit status.
.TP
.if !'po4a'hide' .B 16
At least one of the pages/files/keywords didn't exist or wasn't matched.
.SH ENVIRONMENT
.\".TP \w'MANROFFSEQ\ \ 'u
.TP
.if !'po4a'hide' .B MANPATH
If
.RB $ MANPATH
is set, its value is used as the path to search for manual pages.

See the
.B SEARCH PATH
section of
.BR manpath (5)
for the default behaviour and details of how this environment variable is
handled.
.TP
.if !'po4a'hide' .B MANROFFOPT
Every time
.B man
invokes the formatter
.RB ( nroff ,
.BR troff ,
or
.BR groff ),
it adds the contents of
.RB $ MANROFFOPT
to the formatter's command line.

For example,
.B MANROFFOPT=-P-i
tells the formatter to use italic text (which is only supported by some
terminals) rather than underlined text.
.TP
.if !'po4a'hide' .B MANROFFSEQ
If
.RB $ MANROFFSEQ
is set, its value is used to determine the set of preprocessors to pass
each manual page through.
The default preprocessor list is system dependent.
.TP
.if !'po4a'hide' .B MANSECT
If
.RB $ MANSECT
is set, its value is a colon-delimited list of sections and it is used to
determine which manual sections to search and in what order.
The default is
"%sections%",
unless overridden by the
.B SECTION
directive in
.IR %manpath_config_file% .
.TP
.if !'po4a'hide' .BR MANPAGER , " PAGER"
If
.RB $ MANPAGER
or
.RB $ PAGER
is set
.RB ($ MANPAGER
is used in preference), its value is used as the name of the program used to
display the manual page.
By default,
.B %pager%
is used, falling back to
.B %cat%
if
.B %pager%
is not found or is not executable.

The value may be a simple command name or a command with arguments, and may
use shell quoting (backslashes, single quotes, or double quotes).
It may not use pipes to connect multiple commands; if you need that, use a
wrapper script, which may take the file to display either as an argument or
on standard input.
.TP
.if !'po4a'hide' .B MANLESS
If
.RB $ MANLESS
is set, its value will be used as the default prompt string for the
.B less
pager, as if it had been passed using the
.B \-r
option (so any occurrences of the text
.B $MAN_PN
will be expanded in the same way).
For example, if you want to set the prompt string unconditionally to
\(lqmy prompt string\(rq, set
.RB $ MANLESS
to
.RB \(oq \-Psmy\ prompt\ string \(cq.
Using the
.B \-r
option overrides this environment variable.
.TP
.if !'po4a'hide' .B BROWSER
If
.RB $ BROWSER
is set, its value is a colon-delimited list of commands, each of which in
turn is used to try to start a web browser for
.B man
.BR \-\-html .
In each command,
.I %s
is replaced by a filename containing the HTML output from
.BR groff ,
.I %%
is replaced by a single percent sign (%), and
.I %c
is replaced by a colon (:).
.TP
.if !'po4a'hide' .B SYSTEM
If
.RB $ SYSTEM
is set, it will have the same effect as if it had been specified as the
argument to the
.B \-m
option.
.TP
.if !'po4a'hide' .B MANOPT
If
.RB $ MANOPT
is set, it will be parsed prior to
.B %man%'s
command line and is expected to be in a similar format.
As all of the other
.B %man%
specific environment variables can be expressed as command line options, and
are thus candidates for being included in
.RB $ MANOPT
it is expected that they will become obsolete.
N.B.  All spaces that should be interpreted as part of an option's argument
must be escaped.
.TP
.if !'po4a'hide' .B MANWIDTH
If
.RB $ MANWIDTH
is set, its value is used as the line length for which manual pages should
be formatted.
If it is not set, manual pages will be formatted with a line length
appropriate to the current terminal (using the value of
.RB $ COLUMNS ,
and
.BR ioctl (2)
if available, or falling back to 80 characters if neither is available).
Cat pages will only be saved when the default formatting can be used, that
is when the terminal line length is between 66 and 80 characters.
.TP
.if !'po4a'hide' .B MAN_KEEP_FORMATTING
Normally, when output is not being directed to a terminal (such as to a file
or a pipe), formatting characters are discarded to make it easier to read
the result without special tools.
However, if
.RB $ MAN_KEEP_FORMATTING
is set to any non-empty value, these formatting characters are retained.
This may be useful for wrappers around
.B %man%
that can interpret formatting characters.
.TP
.if !'po4a'hide' .B MAN_KEEP_STDERR
Normally, when output is being directed to a terminal (usually to a pager),
any error output from the command used to produce formatted versions of
manual pages is discarded to avoid interfering with the pager's display.
Programs such as
.B groff
often produce relatively minor error messages about typographical problems
such as poor alignment, which are unsightly and generally confusing when
displayed along with the manual page.
However, some users want to see them anyway, so, if
.RB $ MAN_KEEP_STDERR
is set to any non-empty value, error output will be displayed as usual.
.TP
.if !'po4a'hide' .B MAN_DISABLE_SECCOMP
On Linux,
.B %man%
normally confines subprocesses that handle untrusted data using a
.BR seccomp (2)
sandbox.
This makes it safer to run complex parsing code over arbitrary manual pages.
If this goes wrong for some reason unrelated to the content of the page
being displayed, you can set
.RB $ MAN_DISABLE_SECCOMP
to any non-empty value to disable the sandbox.
.TP
.if !'po4a'hide' .B PIPELINE_DEBUG
If the
.RB $ PIPELINE_DEBUG
environment variable is set to "1", then
.B %man%
will print debugging messages to standard error describing each subprocess
it runs.
.TP
.if !'po4a'hide' .BR LANG , " LC_MESSAGES"
Depending on system and implementation, either or both of
.RB $ LANG
and
.RB $ LC_MESSAGES
will be interrogated for the current message locale.
.B %man%
will display its messages in that locale (if available).
See
.BR setlocale (3)
for precise details.
.SH FILES
.TP
.if !'po4a'hide' .I %manpath_config_file%
man-db configuration file.
.TP
.if !'po4a'hide' .I /usr/share/man
A global manual page hierarchy.
.SH STANDARDS
POSIX.1\-2001, POSIX.1\-2008, POSIX.1\-2017.
.SH "SEE ALSO"
.if !'po4a'hide' .BR %apropos% (1),
.if !'po4a'hide' .BR groff (1),
.if !'po4a'hide' .BR less (1),
.if !'po4a'hide' .BR %manpath% (1),
.if !'po4a'hide' .BR nroff (1),
.if !'po4a'hide' .BR troff (1),
.if !'po4a'hide' .BR %whatis% (1),
.if !'po4a'hide' .BR %zsoelim% (1),
.if !'po4a'hide' .BR manpath (5),
.if !'po4a'hide' .BR man (7),
.if !'po4a'hide' .BR %catman% (8),
.if !'po4a'hide' .BR %mandb% (8)
.PP
Documentation for some packages may be available in other formats, such as
.BR info (1)
or HTML.
.SH HISTORY
1990, 1991 \(en Originally written by John W.\& Eaton (jwe@che.utexas.edu).

Dec 23 1992: Rik Faith (faith@cs.unc.edu) applied bug fixes
supplied by Willem Kasdorp (wkasdo@nikhefk.nikef.nl).

30th April 1994 \(en 23rd February 2000: Wilf.\& (G.Wilford@ee.surrey.ac.uk)
has been developing and maintaining this package
with the help of a few dedicated people.

30th October 1996 \(en 30th March 2001: Fabrizio Polacco <fpolacco@debian.org>
maintained and enhanced this package for the Debian project, with the
help of all the community.

31st March 2001 \(en present day: Colin Watson <cjwatson@debian.org> is now
developing and maintaining man-db.
.SH BUGS
.if !'po4a'hide' https://gitlab.com/man-db/man-db/-/issues
.br
.if !'po4a'hide' https://savannah.nongnu.org/bugs/?group=man-db