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+This is a terse description of the new features added to bash-5.1 since
+the release of bash-5.0. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. `bind -x' now supports different bindings for different editing modes and
+ keymaps.
+
+b. Bash attempts to optimize the number of times it forks when executing
+ commands in subshells and from `bash -c'.
+
+c. Here documents and here strings now use pipes for the expanded document if
+ it's smaller than the pipe buffer size, reverting to temporary files if it's
+ larger.
+
+d. There are new loadable builtins: mktemp, accept, mkfifo, csv, cut/lcut
+
+e. In posix mode, `trap -p' now displays signals whose disposition is SIG_DFL
+ and those that were SIG_IGN when the shell starts.
+
+f. The shell now expands the history number (e.g., in PS1) even if it is not
+ currently saving commands to the history list.
+
+g. `read -e' may now be used with arbitrary file descriptors (`read -u N').
+
+h. The `select' builtin now runs traps if its internal call to the read builtin
+ is interrupted by a signal.
+
+i. SRANDOM: a new variable that expands to a 32-bit random number that is not
+ produced by an LCRNG, and uses getrandom/getentropy, falling back to
+ /dev/urandom or arc4random if available. There is a fallback generator if
+ none of these are available.
+
+j. shell-transpose-words: a new bindable readline command that uses the same
+ definition of word as shell-forward-word, etc.
+
+k. The shell now adds default bindings for shell-forward-word,
+ shell-backward-word, shell-transpose-words, and shell-kill-word.
+
+l. Bash now allows ARGV0 appearing in the initial shell environment to set $0.
+
+m. If `unset' is executed without option arguments, bash tries to unset a shell
+ function if a name argument cannot be a shell variable name because it's not
+ an identifier.
+
+n. The `test -N' operator uses nanosecond timestamp granularity if it's
+ available.
+
+o. Bash posix mode now treats assignment statements preceding shell function
+ definitions the same as in its default mode, since POSIX has changed and
+ no longer requires those assignments to persist after the function returns
+ (POSIX interp 654).
+
+p. BASH_REMATCH is no longer readonly.
+
+q. wait: has a new -p VARNAME option, which stores the PID returned by `wait -n'
+ or `wait' without arguments.
+
+r. Sorting the results of pathname expansion now uses byte-by-byte comparisons
+ if two strings collate equally to impose a total order; the result of a
+ POSIX interpretation.
+
+s. Bash now allows SIGINT trap handlers to execute recursively.
+
+t. Bash now saves and restores state around setting and unsetting posix mode,
+ instead of having unsetting posix mode set a known state.
+
+u. Process substitution is now available in posix mode.
+
+v. READLINE_MARK: a new variable available while executing commands bound with
+ `bind -x', contains the value of the mark.
+
+w. Bash removes SIGCHLD from the set of blocked signals if it's blocked at shell
+ startup.
+
+x. `test -v N' can now test whether or not positional parameter N is set.
+
+y. `local' now honors the `-p' option to display all local variables at the
+ current context.
+
+z. The `@a' variable transformation now prints attributes for unset array
+ variables.
+
+aa. The `@A' variable transformation now prints a declare command that sets a
+ variable's attributes if the variable has attributes but is unset.
+
+bb. `declare' and `local' now have a -I option that inherits attributes and
+ value from a variable with the same name at a previous scope.
+
+cc. When run from a -c command, `jobs' now reports the status of completed jobs.
+
+dd. New `U', `u', and `L' parameter transformations to convert to uppercase,
+ convert first character to uppercase, and convert to lowercase,
+ respectively.
+
+ee. PROMPT_COMMAND: can now be an array variable, each element of which can
+ contain a command to be executed like a string PROMPT_COMMAND variable.
+
+ff. `ulimit' has a -R option to report and set the RLIMIT_RTTIME resource.
+
+gg. Associative arrays may be assigned using a list of key-value pairs within
+ a compound assignment. Compound assignments where the words are not of
+ the form [key]=value are assumed to be key-value assignments. A missing or
+ empty key is an error; a missing value is treated as NULL. Assignments may
+ not mix the two forms.
+
+hh. New `K' parameter transformation to display associative arrays as key-
+ value pairs.
+
+ii. Writing history to syslog now handles messages longer than the syslog max
+ length by writing multiple messages with a sequence number.
+
+jj. SECONDS and RANDOM may now be assigned using arithmetic expressions, since
+ they are nominally integer variables. LINENO is not an integer variable.
+
+kk. Bash temporarily suppresses the verbose option when running the DEBUG trap
+ while running a command from the `fc' builtin.
+
+ll. `wait -n' now accepts a list of job specifications as arguments and will
+ wait for the first one in the list to change state.
+
+mm. The associative array implementation can now dynamically increase the
+ size of the hash table based on insertion patterns.
+
+nn. HISTFILE is now readonly in a restricted shell.
+
+oo. The bash malloc now returns memory that is 16-byte aligned on 64-bit
+ systems.
+
+pp. If the hash builtin is listing hashed filenames portably, don't print
+ anything if the table is empty.
+
+qq. GLOBIGNORE now ignores `.' and `..' as a terminal pathname component.
+
+rr. Bash attempts to optimize away forks in the last command in a function body
+ under appropriate circumstances.
+
+ss. The globbing code now uses fnmatch(3) to check collation elements (if
+ available) even in cases without multibyte characters.
+
+tt. The `fg' and `bg' builtins now return an error in a command substitution
+ when asked to restart a job inherited from the parent shell.
+
+uu. The shell now attempts to unlink all FIFOs on exit, whether a consuming
+ process has finished with them or not.
+
+vv. There is a new contributed loadable builtin: asort.
+
+2. New Features in Readline
+
+a. If a second consecutive completion attempt produces matches where the first
+ did not, treat it as a new completion attempt and insert a match as
+ appropriate.
+
+b. Bracketed paste mode works in more places: incremental search strings, vi
+ overstrike mode, character search, and reading numeric arguments.
+
+c. Readline automatically switches to horizontal scrolling if the terminal has
+ only one line.
+
+d. Unbinding all key sequences bound to a particular readline function now
+ descends into keymaps for multi-key sequences.
+
+e. rl-clear-display: new bindable command that clears the screen and, if
+ possible, the scrollback buffer (bound to emacs mode M-C-l by default).
+
+f. New active mark and face feature: when enabled, it will highlight the text
+ inserted by a bracketed paste (the `active region') and the text found by
+ incremental and non-incremental history searches. This is tied to bracketed
+ paste and can be disabled by turning off bracketed paste.
+
+g. Readline sets the mark in several additional commands.
+
+h. Bracketed paste mode is enabled by default.
+
+i. Readline tries to take advantage of the more regular structure of UTF-8
+ characters to identify the beginning and end of characters when moving
+ through the line buffer.
+
+j. The bindable operate-and-get-next command (and its default bindings) are
+ now part of readline instead of a bash-specific addition.
+
+k. The signal cleanup code now blocks SIGINT while processing after a SIGINT.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-5.0 since
+the release of bash-4.4. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. The `wait' builtin can now wait for the last process substitution created.
+
+b. There is an EPOCHSECONDS variable, which expands to the time in seconds
+ since the Unix epoch.
+
+c. There is an EPOCHREALTIME variable, which expands to the time in seconds
+ since the Unix epoch with microsecond granularity.
+
+d. New loadable builtins: rm, stat, fdflags.
+
+e. BASH_ARGV0: a new variable that expands to $0 and sets $0 on assignment.
+
+f. When supplied a numeric argument, the shell-expand-line bindable readline
+ command does not perform quote removal and suppresses command and process
+ substitution.
+
+g. `history -d' understands negative arguments: negative arguments offset from
+ the end of the history list.
+
+h. The `name' argument to the `coproc' reserved word now undergoes word
+ expansion, so unique coprocs can be created in loops.
+
+i. A nameref name resolution loop in a function now resolves to a variable by
+ that name in the global scope.
+
+j. The `wait' builtin now has a `-f' option, which signifies to wait until the
+ specified job or process terminates, instead of waiting until it changes
+ state.
+
+k. There is a define in config-top.h that allows the shell to use a static
+ value for $PATH, overriding whatever is in the environment at startup, for
+ use by the restricted shell.
+
+l. Process substitution does not inherit the `v' option, like command
+ substitution.
+
+m. If a non-interactive shell with job control enabled detects that a foreground
+ job died due to SIGINT, it acts as if it received the SIGINT.
+
+n. The SIGCHLD trap is run once for each exiting child process even if job
+ control is not enabled when the shell is in Posix mode.
+
+o. A new shopt option: localvar_inherit; if set, a local variable inherits the
+ value of a variable with the same name at the nearest preceding scope.
+
+p. `bind -r' now checks whether a key sequence is bound before binding it to
+ NULL, to avoid creating keymaps for a multi-key sequence.
+
+q. A numeric argument to the line editing `operate-and-get-next' command
+ specifies which history entry to use.
+
+r. The positional parameters are now assigned before running the shell startup
+ files, so startup files can use $@.
+
+s. There is a compile-time option that forces the shell to disable the check
+ for an inherited OLDPWD being a directory.
+
+t. The `history' builtin can now delete ranges of history entries using
+ `-d start-end'.
+
+u. The `vi-edit-and-execute-command' bindable readline command now puts readline
+ back in vi insertion mode after executing commands from the edited file.
+
+v. The command completion code now matches aliases and shell function names
+ case-insensitively if the readline completion-ignore-case variable is set.
+
+w. There is a new `assoc_expand_once' shell option that attempts to expand
+ associative array subscripts only once.
+
+x. The shell only sets up BASH_ARGV and BASH_ARGC at startup if extended
+ debugging mode is active. The old behavior of unconditionally setting them
+ is available as part of the shell compatibility options.
+
+y. The `umask' builtin now allows modes and masks greater than octal 777.
+
+z. The `times' builtin now honors the current locale when printing a decimal
+ point.
+
+aa. There is a new (disabled by default, undocumented) shell option to enable
+ and disable sending history to syslog at runtime.
+
+bb. Bash no longer allows variable assignments preceding a special builtin that
+ changes variable attributes to propagate back to the calling environment
+ unless the compatibility level is 44 or lower.
+
+cc. You can set the default value for $HISTSIZE at build time in config-top.h.
+
+dd. The `complete' builtin now accepts a -I option that applies the completion
+ to the initial word on the line.
+
+ee. The internal bash malloc now uses mmap (if available) to satisfy requests
+ greater than 128K bytes, so free can use mfree to return the pages to the
+ kernel.
+
+ff. The shell doesn't automatically set BASH_ARGC and BASH_ARGV at startup
+ unless it's in debugging mode, as the documentation has always said, but
+ will dynamically create them if a script references them at the top level
+ without having enabled debugging mode.
+
+gg. The localvar_inherit option will not attempt to inherit a value from a
+ variable of an incompatible type (indexed vs. associative arrays, for
+ example).
+
+hh. The `globasciiranges' option is now enabled by default; it can be set to
+ off by default at configuration time.
+
+ii. Associative and indexed arrays now allow subscripts consisting solely of
+ whitespace.
+
+jj. `checkwinsize' is now enabled by default.
+
+kk. The `localvar_unset' shopt option is now visible and documented.
+
+ll. The `progcomp_alias' shopt option is now visible and documented.
+
+mm. The signal name processing code now understands `SIGRTMIN+n' all the way
+ up to SIGRTMAX.
+
+nn. There is a new `seq' loadable builtin.
+
+oo. Trap execution now honors the (internal) max invocations of `eval', since
+ traps are supposed to be executed as if using `eval'.
+
+pp. The $_ variable doesn't change when the shell executes a command that forks.
+
+qq. The `kill' builtin now supports -sSIGNAME and -nSIGNUM, even though
+ conforming applications aren't supposed to use them.
+
+rr. POSIX mode now enables the `shift_verbose' option.
+
+2. New Features in Readline
+
+a. Non-incremental vi-mode search (`N', `n') can search for a shell pattern, as
+ Posix specifies (uses fnmatch(3) if available).
+
+b. There are new `next-screen-line' and `previous-screen-line' bindable
+ commands, which move the cursor to the same column in the next, or previous,
+ physical line, respectively.
+
+c. There are default key bindings for control-arrow-key key combinations.
+
+d. A negative argument (-N) to `quoted-insert' means to insert the next N
+ characters using quoted-insert.
+
+e. New public function: rl_check_signals(), which allows applications to
+ respond to signals that readline catches while waiting for input using
+ a custom read function.
+
+f. There is new support for conditionally testing the readline version in an
+ inputrc file, with a full set of arithmetic comparison operators available.
+
+g. There is a simple variable comparison facility available for use within an
+ inputrc file. Allowable operators are equality and inequality; string
+ variables may be compared to a value; boolean variables must be compared to
+ either `on' or `off'; variable names are separated from the operator by
+ whitespace.
+
+h. The history expansion library now understands command and process
+ substitution and extended globbing and allows them to appear anywhere in a
+ word.
+
+i. The history library has a new variable that allows applications to set the
+ initial quoting state, so quoting state can be inherited from a previous
+ line.
+
+j. Readline now allows application-defined keymap names; there is a new public
+ function, rl_set_keymap_name(), to do that.
+
+k. The "Insert" keypad key, if available, now puts readline into overwrite
+ mode.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-4.4 since
+the release of bash-4.3. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. There is now a settable configuration #define that will cause the shell
+ to exit if the shell is running setuid without the -p option and setuid
+ to the real uid fails.
+
+b. Command and process substitutions now turn off the `-v' option when
+ executing, as other shells seem to do.
+
+c. The default value for the `checkhash' shell option may now be set at
+ compile time with a #define.
+
+d. The `mapfile' builtin now has a -d option to use an arbitrary character
+ as the record delimiter, and a -t option to strip the delimiter as
+ supplied with -d.
+
+e. The maximum number of nested recursive calls to `eval' is now settable in
+ config-top.h; the default is no limit.
+
+f. The `-p' option to declare and similar builtins will display attributes for
+ named variables even when those variables have not been assigned values
+ (which are technically unset).
+
+g. The maximum number of nested recursive calls to `source' is now settable
+ in config-top.h; the default is no limit.
+
+h. All builtin commands recognize the `--help' option and print a usage
+ summary.
+
+i. Bash does not allow function names containing `/' and `=' to be exported.
+
+j. The `ulimit' builtin has new -k (kqueues) and -P (pseudoterminals) options.
+
+k. The shell now allows `time ; othercommand' to time null commands.
+
+l. There is a new `--enable-function-import' configuration option to allow
+ importing shell functions from the environment; import is enabled by
+ default.
+
+m. `printf -v var ""' will now set `var' to the empty string, as if `var=""'
+ had been executed.
+
+n. GLOBIGNORE, the pattern substitution word expansion, and programmable
+ completion match filtering now honor the value of the `nocasematch' option.
+
+o. There is a new ${parameter@spec} family of operators to transform the
+ value of `parameter'.
+
+p. Bash no longer attempts to perform compound assignment if a variable on the
+ rhs of an assignment statement argument to `declare' has the form of a
+ compound assignment (e.g., w='(word)' ; declare foo=$w); compound
+ assignments are accepted if the variable was already declared as an array,
+ but with a warning.
+
+q. The declare builtin no longer displays array variables using the compound
+ assignment syntax with quotes; that will generate warnings when re-used as
+ input, and isn't necessary.
+
+r. Executing the rhs of && and || will no longer cause the shell to fork if
+ it's not necessary.
+
+s. The `local' builtin takes a new argument: `-', which will cause it to save
+ and the single-letter shell options and restore their previous values at
+ function return.
+
+t. `complete' and `compgen' have a new `-o nosort' option, which forces
+ readline to not sort the completion matches.
+
+u. Bash now allows waiting for the most recent process substitution, since it
+ appears as $!.
+
+v. The `unset' builtin now unsets a scalar variable if it is subscripted with
+ a `0', analogous to the ${var[0]} expansion.
+
+w. `set -i' is no longer valid, as in other shells.
+
+x. BASH_SUBSHELL is now updated for process substitution and group commands
+ in pipelines, and is available with the same value when running any exit
+ trap.
+
+y. Bash now checks $INSIDE_EMACS as well as $EMACS when deciding whether or
+ not bash is being run in a GNU Emacs shell window.
+
+z. Bash now treats SIGINT received when running a non-builtin command in a
+ loop the way it has traditionally treated running a builtin command:
+ running any trap handler and breaking out of the loop.
+
+aa. New variable: EXECIGNORE; a colon-separate list of patterns that will
+ cause matching filenames to be ignored when searching for commands.
+
+bb. Aliases whose value ends in a shell metacharacter now expand in a way to
+ allow them to be `pasted' to the next token, which can potentially change
+ the meaning of a command (e.g., turning `&' into `&&').
+
+cc. `make install' now installs the example loadable builtins and a set of
+ bash headers to use when developing new loadable builtins.
+
+dd. `enable -f' now attempts to call functions named BUILTIN_builtin_load when
+ loading BUILTIN, and BUILTIN_builtin_unload when deleting it. This allows
+ loadable builtins to run initialization and cleanup code.
+
+ee. There is a new BASH_LOADABLES_PATH variable containing a list of directories
+ where the `enable -f' command looks for shared objects containing loadable
+ builtins.
+
+ff. The `complete_fullquote' option to `shopt' changes filename completion to
+ quote all shell metacharacters in filenames and directory names.
+
+gg. The `kill' builtin now has a `-L' option, equivalent to `-l', for
+ compatibility with Linux standalone versions of kill.
+
+hh. BASH_COMPAT and FUNCNEST can be inherited and set from the shell's initial
+ environment.
+
+ii. inherit_errexit: a new `shopt' option that, when set, causes command
+ substitutions to inherit the -e option. By default, those subshells disable
+ -e. It's enabled as part of turning on posix mode.
+
+jj. New prompt string: PS0. Expanded and displayed by interactive shells after
+ reading a complete command but before executing it.
+
+kk. Interactive shells now behave as if SIGTSTP/SIGTTIN/SIGTTOU are set to
+ SIG_DFL when the shell is started, so they are set to SIG_DFL in child
+ processes.
+
+ll. Posix-mode shells now allow double quotes to quote the history expansion
+ character.
+
+mm. OLDPWD can be inherited from the environment if it names a directory.
+
+nn. Shells running as root no longer inherit PS4 from the environment, closing
+ a security hole involving PS4 expansion performing command substitution.
+
+oo. If executing an implicit `cd' when the `autocd' option is set, bash will
+ now invoke a function named `cd' if one exists before executing the `cd'
+ builtin.
+
+pp. Value conversions (arithmetic expansions, case modification, etc.) now
+ happen when assigning elements of an array using compound assignment.
+
+qq. There is a new option settable in config-top.h that makes multiple
+ directory arguments to `cd' a fatal error.
+
+rr. Bash now uses mktemp() when creating internal temporary files; it produces
+ a warning at build time on many Linux systems.
+
+2. New Features in Readline
+
+a. The history truncation code now uses the same error recovery mechanism as
+ the history writing code, and restores the old version of the history file
+ on error. The error recovery mechanism handles symlinked history files.
+
+b. There is a new bindable variable, `enable-bracketed-paste', which enables
+ support for a terminal's bracketed paste mode.
+
+c. The editing mode indicators can now be strings and are user-settable
+ (new `emacs-mode-string', `vi-cmd-mode-string' and `vi-ins-mode-string'
+ variables). Mode strings can contain invisible character sequences.
+ Setting mode strings to null strings restores the defaults.
+
+d. Prompt expansion adds the mode string to the last line of a multi-line
+ prompt (one with embedded newlines).
+
+e. There is a new bindable variable, `colored-completion-prefix', which, if
+ set, causes the common prefix of a set of possible completions to be
+ displayed in color.
+
+f. There is a new bindable command `vi-yank-pop', a vi-mode version of emacs-
+ mode yank-pop.
+
+g. The redisplay code underwent several efficiency improvements for multibyte
+ locales.
+
+h. The insert-char function attempts to batch-insert all pending typeahead
+ that maps to self-insert, as long as it is coming from the terminal.
+
+i. rl_callback_sigcleanup: a new application function that can clean up and
+ unset any state set by readline's callback mode. Intended to be used
+ after a signal.
+
+j. If an incremental search string has its last character removed with DEL, the
+ resulting empty search string no longer matches the previous line.
+
+k. If readline reads a history file that begins with `#' (or the value of
+ the history comment character) and has enabled history timestamps, the
+ history entries are assumed to be delimited by timestamps. This allows
+ multi-line history entries.
+
+l. Readline now throws an error if it parses a key binding without a
+ terminating `:' or whitespace.
+
+m. The default binding for ^W in vi mode now uses word boundaries specified
+ by Posix (vi-unix-word-rubout is bindable command name).
+
+n. rl_clear_visible_line: new application-callable function; clears all
+ screen lines occupied by the current visible readline line.
+
+o. rl_tty_set_echoing: application-callable function that controls whether
+ or not readline thinks it is echoing terminal output.
+
+p. Handle >| and strings of digits preceding and following redirection
+ specifications as single tokens when tokenizing the line for history
+ expansion.
+
+q. Fixed a bug with displaying completions when the prefix display length
+ is greater than the length of the completions to be displayed.
+
+r. The :p history modifier now applies to the entire line, so any expansion
+ specifying :p causes the line to be printed instead of expanded.
+
+s. New application-callable function: rl_pending_signal(): returns the signal
+ number of any signal readline has caught but not yet handled.
+
+t. New application-settable variable: rl_persistent_signal_handlers: if set
+ to a non-zero value, readline will enable the readline-6.2 signal handler
+ behavior in callback mode: handlers are installed when
+ rl_callback_handler_install is called and removed removed when a complete
+ line has been read.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-4.3 since
+the release of bash-4.2. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. The `helptopic' completion action now maps to all the help topics, not just
+ the shell builtins.
+
+b. The `help' builtin no longer does prefix substring matching first, so
+ `help read' does not match `readonly', but will do it if exact string
+ matching fails.
+
+c. The shell can be compiled to not display a message about processes that
+ terminate due to SIGTERM.
+
+d. Non-interactive shells now react to the setting of checkwinsize and set
+ LINES and COLUMNS after a foreground job exits.
+
+e. There is a new shell option, `globasciiranges', which, when set to on,
+ forces globbing range comparisons to use character ordering as if they
+ were run in the C locale.
+
+f. There is a new shell option, `direxpand', which makes filename completion
+ expand variables in directory names in the way bash-4.1 did.
+
+g. In Posix mode, the `command' builtin does not change whether or not a
+ builtin it shadows is treated as an assignment builtin.
+
+h. The `return' and `exit' builtins accept negative exit status arguments.
+
+i. The word completion code checks whether or not a filename containing a
+ shell variable expands to a directory name and appends `/' to the word
+ as appropriate. The same code expands shell variables in command names
+ when performing command completion.
+
+j. In Posix mode, it is now an error to attempt to define a shell function
+ with the same name as a Posix special builtin.
+
+k. When compiled for strict Posix conformance, history expansion is disabled
+ by default.
+
+l. The history expansion character (!) does not cause history expansion when
+ followed by the closing quote in a double-quoted string.
+
+m. `complete' and its siblings compgen/compopt now takes a new `-o noquote'
+ option to inhibit quoting of the completions.
+
+n. Setting HISTSIZE to a value less than zero causes the history list to be
+ unlimited (setting it 0 zero disables the history list).
+
+o. Setting HISTFILESIZE to a value less than zero causes the history file size
+ to be unlimited (setting it to 0 causes the history file to be truncated
+ to zero size).
+
+p. The `read' builtin now skips NUL bytes in the input.
+
+q. There is a new `bind -X' option to print all key sequences bound to Unix
+ commands.
+
+r. When in Posix mode, `read' is interruptible by a trapped signal. After
+ running the trap handler, read returns 128+signal and throws away any
+ partially-read input.
+
+s. The command completion code skips whitespace and assignment statements
+ before looking for the command name word to be completed.
+
+t. The build process has a new mechanism for constructing separate help files
+ that better reflects the current set of compilation options.
+
+u. The -nt and -ot options to test now work with files with nanosecond
+ timestamp resolution.
+
+v. The shell saves the command history in any shell for which history is
+ enabled and HISTFILE is set, not just interactive shells.
+
+w. The shell has `nameref' variables and new -n(/+n) options to declare and
+ unset to use them, and a `test -R' option to test for them.
+
+x. The shell now allows assigning, referencing, and unsetting elements of
+ indexed arrays using negative subscripts (a[-1]=2, echo ${a[-1]}) which
+ count back from the last element of the array.
+
+y. The {x}<word redirection feature now allows words like {array[ind]} and
+ can use variables with special meanings to the shell (e.g., BASH_XTRACEFD).
+
+z. There is a new CHILD_MAX special shell variable; its value controls the
+ number of exited child statues the shell remembers.
+
+aa. There is a new configuration option (--enable-direxpand-default) that
+ causes the `direxpand' shell option to be enabled by default.
+
+bb. Bash does not do anything special to ensure that the file descriptor
+ assigned to X in {x}<foo remains open after the block containing it
+ completes.
+
+cc. The `wait' builtin has a new `-n' option to wait for the next child to
+ change status.
+
+dd. The `printf' %(...)T format specifier now uses the current time if no
+ argument is supplied.
+
+ee. There is a new variable, BASH_COMPAT, that controls the current shell
+ compatibility level.
+
+ff. The `popd' builtin now treats additional arguments as errors.
+
+gg. The brace expansion code now treats a failed sequence expansion as a
+ simple string and will continue to expand brace terms in the remainder
+ of the word.
+
+hh. Shells started to run process substitutions now run any trap set on EXIT.
+
+ii. The fc builtin now interprets -0 as the current command line.
+
+jj. Completing directory names containing shell variables now adds a trailing
+ slash if the expanded result is a directory.
+
+kk. `cd' has a new `-@' option to browse a file's extended attributes on
+ systems that support O_XATTR.
+
+ll. The test/[/[[ `-v variable' binary operator now understands array
+ references.
+
+2. New Features in Readline
+
+a. Readline is now more responsive to SIGHUP and other fatal signals when
+ reading input from the terminal or performing word completion but no
+ longer attempts to run any not-allowable functions from a signal handler
+ context.
+
+b. There are new bindable commands to search the history for the string of
+ characters between the beginning of the line and the point
+ (history-substring-search-forward, history-substring-search-backward)
+
+c. Readline allows quoted strings as the values of variables when setting
+ them with `set'. As a side effect, trailing spaces and tabs are ignored
+ when setting a string variable's value.
+
+d. The history library creates a backup of the history file when writing it
+ and restores the backup on a write error.
+
+e. New application-settable variable: rl_filename_stat_hook: a function called
+ with a filename before using it in a call to stat(2). Bash uses it to
+ expand shell variables so things like $HOME/Downloads have a slash
+ appended.
+
+f. New bindable function `print-last-kbd-macro', prints the most-recently-
+ defined keyboard macro in a reusable format.
+
+g. New user-settable variable `colored-stats', enables use of colored text
+ to denote file types when displaying possible completions (colored analog
+ of visible-stats).
+
+h. New user-settable variable `keyseq-timout', acts as an inter-character
+ timeout when reading input or incremental search strings.
+
+i. New application-callable function: rl_clear_history. Clears the history list
+ and frees all readline-associated private data.
+
+j. New user-settable variable, show-mode-in-prompt, adds a characters to the
+ beginning of the prompt indicating the current editing mode.
+
+k. New application-settable variable: rl_input_available_hook; function to be
+ called when readline detects there is data available on its input file
+ descriptor.
+
+l. Readline calls an application-set event hook (rl_event_hook) after it gets
+ a signal while reading input (read returns -1/EINTR but readline does not
+ handle the signal immediately) to allow the application to handle or
+ otherwise note it.
+
+m. If the user-settable variable `history-size' is set to a value less than
+ 0, the history list size is unlimited.
+
+n. New application-settable variable: rl_signal_event_hook; function that is
+ called when readline is reading terminal input and read(2) is interrupted
+ by a signal. Currently not called for SIGHUP or SIGTERM.
+
+o. rl_change_environment: new application-settable variable that controls
+ whether or not Readline modifies the environment (currently readline
+ modifies only LINES and COLUMNS).
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-4.2 since
+the release of bash-4.1. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. `exec -a foo' now sets $0 to `foo' in an executable shell script without a
+ leading #!.
+
+b. Subshells begun to execute command substitutions or run shell functions or
+ builtins in subshells do not reset trap strings until a new trap is
+ specified. This allows $(trap) to display the caller's traps and the
+ trap strings to persist until a new trap is set.
+
+c. `trap -p' will now show signals ignored at shell startup, though their
+ disposition still cannot be modified.
+
+d. $'...', echo, and printf understand \uXXXX and \UXXXXXXXX escape sequences.
+
+e. declare/typeset has a new `-g' option, which creates variables in the
+ global scope even when run in a shell function.
+
+f. test/[/[[ have a new -v variable unary operator, which returns success if
+ `variable' has been set.
+
+g. Posix parsing changes to allow `! time command' and multiple consecutive
+ instances of `!' (which toggle) and `time' (which have no cumulative
+ effect).
+
+h. Posix change to allow `time' as a command by itself to print the elapsed
+ user, system, and real times for the shell and its children.
+
+j. $((...)) is always parsed as an arithmetic expansion first, instead of as
+ a potential nested command substitution, as Posix requires.
+
+k. A new FUNCNEST variable to allow the user to control the maximum shell
+ function nesting (recursive execution) level.
+
+l. The mapfile builtin now supplies a third argument to the callback command:
+ the line about to be assigned to the supplied array index.
+
+m. The printf builtin has a new %(fmt)T specifier, which allows time values
+ to use strftime-like formatting.
+
+n. There is a new `compat41' shell option.
+
+o. The cd builtin has a new Posix-mandated `-e' option.
+
+p. Negative subscripts to indexed arrays, previously errors, now are treated
+ as offsets from the maximum assigned index + 1.
+
+q. Negative length specifications in the ${var:offset:length} expansion,
+ previously errors, are now treated as offsets from the end of the variable.
+
+r. Parsing change to allow `time -p --'.
+
+s. Posix-mode parsing change to not recognize `time' as a keyword if the
+ following token begins with a `-'. This means no more Posix-mode
+ `time -p'. Posix interpretation 267.
+
+t. There is a new `lastpipe' shell option that runs the last command of a
+ pipeline in the current shell context. The lastpipe option has no
+ effect if job control is enabled.
+
+u. History expansion no longer expands the `$!' variable expansion.
+
+v. Posix mode shells no longer exit if a variable assignment error occurs
+ with an assignment preceding a command that is not a special builtin.
+
+w. Non-interactive mode shells exit if -u is enabled and an attempt is made
+ to use an unset variable with the % or # expansions, the `//', `^', or
+ `,' expansions, or the parameter length expansion.
+
+x. Posix-mode shells use the argument passed to `.' as-is if a $PATH search
+ fails, effectively searching the current directory. Posix-2008 change.
+
+2. New Features in Readline
+
+a. The history library does not try to write the history filename in the
+ current directory if $HOME is unset. This closes a potential security
+ problem if the application does not specify a history filename.
+
+b. New bindable variable `completion-display-width' to set the number of
+ columns used when displaying completions.
+
+c. New bindable variable `completion-case-map' to cause case-insensitive
+ completion to treat `-' and `_' as identical.
+
+d. There are new bindable vi-mode command names to avoid readline's case-
+ insensitive matching not allowing them to be bound separately.
+
+e. New bindable variable `menu-complete-display-prefix' causes the menu
+ completion code to display the common prefix of the possible completions
+ before cycling through the list, instead of after.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-4.1 since
+the release of bash-4.0. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. Here-documents within $(...) command substitutions may once more be
+ delimited by the closing right paren, instead of requiring a newline.
+
+b. Bash's file status checks (executable, readable, etc.) now take file
+ system ACLs into account on file systems that support them.
+
+c. Bash now passes environment variables with names that are not valid
+ shell variable names through into the environment passed to child
+ processes.
+
+d. The `execute-unix-command' readline function now attempts to clear and
+ reuse the current line rather than move to a new one after the command
+ executes.
+
+e. `printf -v' can now assign values to array indices.
+
+f. New `complete -E' and `compopt -E' options that work on the "empty"
+ completion: completion attempted on an empty command line.
+
+g. New complete/compgen/compopt -D option to define a `default' completion:
+ a completion to be invoked on command for which no completion has been
+ defined. If this function returns 124, programmable completion is
+ attempted again, allowing a user to dynamically build a set of completions
+ as completion is attempted by having the default completion function
+ install individual completion functions each time it is invoked.
+
+h. When displaying associative arrays, subscripts are now quoted.
+
+i. Changes to dabbrev-expand to make it more `emacs-like': no space appended
+ after matches, completions are not sorted, and most recent history entries
+ are presented first.
+
+j. The [[ and (( commands are now subject to the setting of `set -e' and the
+ ERR trap.
+
+k. The source/. builtin now removes NUL bytes from the file before attempting
+ to parse commands.
+
+l. There is a new configuration option (in config-top.h) that forces bash to
+ forward all history entries to syslog.
+
+m. A new variable $BASHOPTS to export shell options settable using `shopt' to
+ child processes.
+
+n. There is a new confgure option that forces the extglob option to be
+ enabled by default.
+
+o. New variable $BASH_XTRACEFD; when set to an integer bash will write xtrace
+ output to that file descriptor.
+
+p. If the optional left-hand-side of a redirection is of the form {var}, the
+ shell assigns the file descriptor used to $var or uses $var as the file
+ descriptor to move or close, depending on the redirection operator.
+
+q. The < and > operators to the [[ conditional command now do string
+ comparison according to the current locale if the compatibility level
+ is greater than 40.
+
+r. Programmable completion now uses the completion for `b' instead of `a'
+ when completion is attempted on a line like: a $(b c.
+
+s. Force extglob on temporarily when parsing the pattern argument to
+ the == and != operators to the [[ command, for compatibility.
+
+t. Changed the behavior of interrupting the wait builtin when a SIGCHLD is
+ received and a trap on SIGCHLD is set to be Posix-mode only.
+
+u. The read builtin has a new `-N nchars' option, which reads exactly NCHARS
+ characters, ignoring delimiters like newline.
+
+v. The mapfile/readarray builtin no longer stores the commands it invokes via
+ callbacks in the history list.
+
+w. There is a new `compat40' shopt option.
+
+2. New Features in Readline
+
+a. New bindable function: menu-complete-backward.
+
+b. In the vi insertion keymap, C-n is now bound to menu-complete by default,
+ and C-p to menu-complete-backward.
+
+c. When in vi command mode, repeatedly hitting ESC now does nothing, even
+ when ESC introduces a bound key sequence. This is closer to how
+ historical vi behaves.
+
+d. New bindable function: skip-csi-sequence. Can be used as a default to
+ consume key sequences generated by keys like Home and End without having
+ to bind all keys.
+
+e. New application-settable function: rl_filename_rewrite_hook. Can be used
+ to rewite or modify filenames read from the file system before they are
+ compared to the word to be completed.
+
+f. New bindable variable: skip-completed-text, active when completing in the
+ middle of a word. If enabled, it means that characters in the completion
+ that match characters in the remainder of the word are "skipped" rather
+ than inserted into the line.
+
+g. The pre-readline-6.0 version of menu completion is available as
+ "old-menu-complete" for users who do not like the readline-6.0 version.
+
+h. New bindable variable: echo-control-characters. If enabled, and the
+ tty ECHOCTL bit is set, controls the echoing of characters corresponding
+ to keyboard-generated signals.
+
+i. New bindable variable: enable-meta-key. Controls whether or not readline
+ sends the smm/rmm sequences if the terminal indicates it has a meta key
+ that enables eight-bit characters.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-4.0 since
+the release of bash-3.2. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. When using substring expansion on the positional parameters, a starting
+ index of 0 now causes $0 to be prefixed to the list.
+
+b. The `help' builtin now prints its columns with entries sorted vertically
+ rather than horizontally.
+
+c. There is a new variable, $BASHPID, which always returns the process id of
+ the current shell.
+
+d. There is a new `autocd' option that, when enabled, causes bash to attempt
+ to `cd' to a directory name that is supplied as the first word of a
+ simple command.
+
+e. There is a new `checkjobs' option that causes the shell to check for and
+ report any running or stopped jobs at exit.
+
+f. The programmable completion code exports a new COMP_TYPE variable, set to
+ a character describing the type of completion being attempted.
+
+g. The programmable completion code exports a new COMP_KEY variable, set to
+ the character that caused the completion to be invoked (e.g., TAB).
+
+h. If creation of a child process fails due to insufficient resources, bash
+ will try again several times before reporting failure.
+
+i. The programmable completion code now uses the same set of characters as
+ readline when breaking the command line into a list of words.
+
+j. The block multiplier for the ulimit -c and -f options is now 512 when in
+ Posix mode, as Posix specifies.
+
+k. Changed the behavior of the read builtin to save any partial input received
+ in the specified variable when the read builtin times out. This also
+ results in variables specified as arguments to read to be set to the empty
+ string when there is no input available. When the read builtin times out,
+ it returns an exit status greater than 128.
+
+l. The shell now has the notion of a `compatibility level', controlled by
+ new variables settable by `shopt'. Setting this variable currently
+ restores the bash-3.1 behavior when processing quoted strings on the rhs
+ of the `=~' operator to the `[[' command.
+
+m. The `ulimit' builtin now has new -b (socket buffer size) and -T (number
+ of threads) options.
+
+n. The -p option to `declare' now displays all variable values and attributes
+ (or function values and attributes if used with -f).
+
+o. There is a new `compopt' builtin that allows completion functions to modify
+ completion options for existing completions or the completion currently
+ being executed.
+
+p. The `read' builtin has a new -i option which inserts text into the reply
+ buffer when using readline.
+
+q. A new `-E' option to the complete builtin allows control of the default
+ behavior for completion on an empty line.
+
+r. There is now limited support for completing command name words containing
+ globbing characters.
+
+s. Changed format of internal help documentation for all builtins to roughly
+ follow man page format.
+
+t. The `help' builtin now has a new -d option, to display a short description,
+ and a -m option, to print help information in a man page-like format.
+
+u. There is a new `mapfile' builtin to populate an array with lines from a
+ given file. The name `readarray' is a synonym.
+
+v. If a command is not found, the shell attempts to execute a shell function
+ named `command_not_found_handle', supplying the command words as the
+ function arguments.
+
+w. There is a new shell option: `globstar'. When enabled, the globbing code
+ treats `**' specially -- it matches all directories (and files within
+ them, when appropriate) recursively.
+
+x. There is a new shell option: `dirspell'. When enabled, the filename
+ completion code performs spelling correction on directory names during
+ completion.
+
+y. The `-t' option to the `read' builtin now supports fractional timeout
+ values.
+
+z. Brace expansion now allows zero-padding of expanded numeric values and
+ will add the proper number of zeroes to make sure all values contain the
+ same number of digits.
+
+aa. There is a new bash-specific bindable readline function: `dabbrev-expand'.
+ It uses menu completion on a set of words taken from the history list.
+
+bb. The command assigned to a key sequence with `bind -x' now sets two new
+ variables in the environment of the executed command: READLINE_LINE_BUFFER
+ and READLINE_POINT. The command can change the current readline line
+ and cursor position by modifying READLINE_LINE_BUFFER and READLINE_POINT,
+ respectively.
+
+cc. There is a new &>> redirection operator, which appends the standard output
+ and standard error to the named file.
+
+dd. The parser now understands `|&' as a synonym for `2>&1 |', which redirects
+ the standard error for a command through a pipe.
+
+ee. The new `;&' case statement action list terminator causes execution to
+ continue with the action associated with the next pattern in the
+ statement rather than terminating the command.
+
+ff. The new `;;&' case statement action list terminator causes the shell to
+ test the next set of patterns after completing execution of the current
+ action, rather than terminating the command.
+
+gg. The shell understands a new variable: PROMPT_DIRTRIM. When set to an
+ integer value greater than zero, prompt expansion of \w and \W will
+ retain only that number of trailing pathname components and replace
+ the intervening characters with `...'.
+
+hh. There are new case-modifying word expansions: uppercase (^[^]) and
+ lowercase (,[,]). They can work on either the first character or
+ array element, or globally. They accept an optional shell pattern
+ that determines which characters to modify. There is an optionally-
+ configured feature to include capitalization operators.
+
+ii. The shell provides associative array variables, with the appropriate
+ support to create, delete, assign values to, and expand them.
+
+jj. The `declare' builtin now has new -l (convert value to lowercase upon
+ assignment) and -u (convert value to uppercase upon assignment) options.
+ There is an optionally-configurable -c option to capitalize a value at
+ assignment.
+
+kk. There is a new `coproc' reserved word that specifies a coprocess: an
+ asynchronous command run with two pipes connected to the creating shell.
+ Coprocs can be named. The input and output file descriptors and the
+ PID of the coprocess are available to the calling shell in variables
+ with coproc-specific names.
+
+ll. A value of 0 for the -t option to `read' now returns success if there is
+ input available to be read from the specified file descriptor.
+
+mm. CDPATH and GLOBIGNORE are ignored when the shell is running in privileged
+ mode.
+
+nn. New bindable readline functions shell-forward-word and shell-backward-word,
+ which move forward and backward words delimited by shell metacharacters
+ and honor shell quoting.
+
+oo. New bindable readline functions shell-backward-kill-word and shell-kill-word
+ which kill words backward and forward, but use the same word boundaries
+ as shell-forward-word and shell-backward-word.
+
+2. New Features in Readline
+
+a. A new variable, rl_sort_completion_matches; allows applications to inhibit
+ match list sorting (but beware: some things don't work right if
+ applications do this).
+
+b. A new variable, rl_completion_invoking_key; allows applications to discover
+ the key that invoked rl_complete or rl_menu_complete.
+
+c. The functions rl_block_sigint and rl_release_sigint are now public and
+ available to calling applications who want to protect critical sections
+ (like redisplay).
+
+d. The functions rl_save_state and rl_restore_state are now public and
+ available to calling applications; documented rest of readline's state
+ flag values.
+
+e. A new user-settable variable, `history-size', allows setting the maximum
+ number of entries in the history list.
+
+f. There is a new implementation of menu completion, with several improvements
+ over the old; the most notable improvement is a better `completions
+ browsing' mode.
+
+g. The menu completion code now uses the rl_menu_completion_entry_function
+ variable, allowing applications to provide their own menu completion
+ generators.
+
+h. There is support for replacing a prefix of a pathname with a `...' when
+ displaying possible completions. This is controllable by setting the
+ `completion-prefix-display-length' variable. Matches with a common prefix
+ longer than this value have the common prefix replaced with `...'.
+
+i. There is a new `revert-all-at-newline' variable. If enabled, readline will
+ undo all outstanding changes to all history lines when `accept-line' is
+ executed.
+
+j. If the kernel supports it, readline displays special characters
+ corresponding to a keyboard-generated signal when the signal is received.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-3.2 since
+the release of bash-3.1. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. Changed the parameter pattern replacement functions to not anchor the
+ pattern at the beginning of the string if doing global replacement - that
+ combination doesn't make any sense.
+
+b. When running in `word expansion only' mode (--wordexp option), inhibit
+ process substitution.
+
+c. Loadable builtins now work on MacOS X 10.[34].
+
+d. Shells running in posix mode no longer set $HOME, as POSIX requires.
+
+e. The code that checks for binary files being executed as shell scripts now
+ checks only for NUL rather than any non-printing character.
+
+f. Quoting the string argument to the [[ command's =~ operator now forces
+ string matching, as with the other pattern-matching operators.
+
+2. New Features in Readline
+
+a. Calling applications can now set the keyboard timeout to 0, allowing
+ poll-like behavior.
+
+b. The value of SYS_INPUTRC (configurable at compilation time) is now used as
+ the default last-ditch startup file.
+
+c. The history file reading functions now allow windows-like \r\n line
+ terminators.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-3.1 since
+the release of bash-3.0. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. Bash now understands LC_TIME as a special variable so that time display
+ tracks the current locale.
+
+b. BASH_ARGC, BASH_ARGV, BASH_SOURCE, and BASH_LINENO are no longer created
+ as `invisible' variables and may not be unset.
+
+c. In POSIX mode, if `xpg_echo' option is enabled, the `echo' builtin doesn't
+ try to interpret any options at all, as POSIX requires.
+
+d. The `bg' builtin now accepts multiple arguments, as POSIX seems to specify.
+
+e. Fixed vi-mode word completion and glob expansion to perform tilde
+ expansion.
+
+f. The `**' mathematic exponentiation operator is now right-associative.
+
+g. The `ulimit' builtin has new options: -i (max number of pending signals),
+ -q (max size of POSIX message queues), and -x (max number of file locks).
+
+h. A bare `%' once again expands to the current job when used as a job
+ specifier.
+
+i. The `+=' assignment operator (append to the value of a string or array) is
+ now supported for assignment statements and arguments to builtin commands
+ that accept assignment statements.
+
+j. BASH_COMMAND now preserves its value when a DEBUG trap is executed.
+
+k. The `gnu_errfmt' option is enabled automatically if the shell is running
+ in an emacs terminal window.
+
+l. New configuration option: --single-help-strings. Causes long help text
+ to be written as a single string; intended to ease translation.
+
+m. The COMP_WORDBREAKS variable now causes the list of word break characters
+ to be emptied when the variable is unset.
+
+n. An unquoted expansion of $* when $IFS is empty now causes the positional
+ parameters to be concatenated if the expansion doesn't undergo word
+ splitting.
+
+o. Bash now inherits $_ from the environment if it appears there at startup.
+
+p. New shell option: nocasematch. If non-zero, shell pattern matching ignores
+ case when used by `case' and `[[' commands.
+
+q. The `printf' builtin takes a new option: -v var. That causes the output
+ to be placed into var instead of on stdout.
+
+r. By default, the shell no longer reports processes dying from SIGPIPE.
+
+s. Bash now sets the extern variable `environ' to the export environment it
+ creates, so C library functions that call getenv() (and can't use the
+ shell-provided replacement) get current values of environment variables.
+
+t. A new configuration option, `--enable-strict-posix-default', which will
+ build bash to be POSIX conforming by default.
+
+u. If compiled for strict POSIX conformance, LINES and COLUMNS may now
+ override the true terminal size.
+
+2. New Features in Readline
+
+a. The key sequence sent by the keypad `delete' key is now automatically
+ bound to delete-char.
+
+b. A negative argument to menu-complete now cycles backward through the
+ completion list.
+
+c. A new bindable readline variable: bind-tty-special-chars. If non-zero,
+ readline will bind the terminal special characters to their readline
+ equivalents when it's called (on by default).
+
+d. New bindable command: vi-rubout. Saves deleted text for possible
+ reinsertion, as with any vi-mode `text modification' command; `X' is bound
+ to this in vi command mode.
+
+e. A new external application-controllable variable that allows the LINES
+ and COLUMNS environment variables to set the window size regardless of
+ what the kernel returns: rl_prefer_env_winsize
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-3.0 since
+the release of bash-2.05b. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. ANSI string expansion now implements the \x{hexdigits} escape.
+
+b. There is a new loadable `strftime' builtin.
+
+c. New variable, COMP_WORDBREAKS, which controls the readline completer's
+ idea of word break characters.
+
+d. The `type' builtin no longer reports on aliases unless alias expansion
+ will actually be performed.
+
+e. HISTCONTROL is now a colon-separated list of values, which permits
+ more extensibility and backwards compatibility.
+
+f. HISTCONTROL may now include the `erasedups' option, which causes all lines
+ matching a line being added to be removed from the history list.
+
+g. `configure' has a new `--enable-multibyte' argument that permits multibyte
+ character support to be disabled even on systems that support it.
+
+h. New variables to support the bash debugger: BASH_ARGC, BASH_ARGV,
+ BASH_SOURCE, BASH_LINENO, BASH_SUBSHELL, BASH_EXECUTION_STRING,
+ BASH_COMMAND
+
+i. FUNCNAME has been changed to support the debugger: it's now an array
+ variable.
+
+j. for, case, select, arithmetic commands now keep line number information
+ for the debugger.
+
+k. There is a new `RETURN' trap executed when a function or sourced script
+ returns (not inherited child processes; inherited by command substitution
+ if function tracing is enabled and the debugger is active).
+
+l. New invocation option: --debugger. Enables debugging and turns on new
+ `extdebug' shell option.
+
+m. New `functrace' and `errtrace' options to `set -o' cause DEBUG and ERR
+ traps, respectively, to be inherited by shell functions. Equivalent to
+ `set -T' and `set -E' respectively. The `functrace' option also controls
+ whether or not the DEBUG trap is inherited by sourced scripts.
+
+n. The DEBUG trap is run before binding the variable and running the action
+ list in a `for' command, binding the selection variable and running the
+ query in a `select' command, and before attempting a match in a `case'
+ command.
+
+o. New `--enable-debugger' option to `configure' to compile in the debugger
+ support code.
+
+p. `declare -F' now prints out extra line number and source file information
+ if the `extdebug' option is set.
+
+q. If `extdebug' is enabled, a non-zero return value from a DEBUG trap causes
+ the next command to be skipped, and a return value of 2 while in a
+ function or sourced script forces a `return'.
+
+r. New `caller' builtin to provide a call stack for the bash debugger.
+
+s. The DEBUG trap is run just before the first command in a function body is
+ executed, for the debugger.
+
+t. `for', `select', and `case' command heads are printed when `set -x' is
+ enabled.
+
+u. There is a new {x..y} brace expansion, which is shorthand for {x.x+1,
+ x+2,...,y}. x and y can be integers or single characters; the sequence
+ may ascend or descend; the increment is always 1.
+
+v. New ksh93-like ${!array[@]} expansion, expands to all the keys (indices)
+ of array.
+
+w. New `force_fignore' shopt option; if enabled, suffixes specified by
+ FIGNORE cause words to be ignored when performing word completion even
+ if they're the only possibilities.
+
+x. New `gnu_errfmt' shopt option; if enabled, error messages follow the `gnu
+ style' (filename:lineno:message) format.
+
+y. New `-o bashdefault' option to complete and compgen; if set, causes the
+ whole set of bash completions to be performed if the compspec doesn't
+ result in a match.
+
+z. New `-o plusdirs' option to complete and compgen; if set, causes directory
+ name completion to be performed and the results added to the rest of the
+ possible completions.
+
+aa. `kill' is available as a builtin even when the shell is built without
+ job control.
+
+bb. New HISTTIMEFORMAT variable; value is a format string to pass to
+ strftime(3). If set and not null, the `history' builtin prints out
+ timestamp information according to the specified format when displaying
+ history entries. If set, bash tells the history library to write out
+ timestamp information when the history file is written.
+
+cc. The [[ ... ]] command has a new binary `=~' operator that performs
+ extended regular expression (egrep-like) matching.
+
+dd. `configure' has a new `--enable-cond-regexp' option (enabled by default)
+ to enable the =~ operator and regexp matching in [[ ... ]].
+
+ee. Subexpressions matched by the =~ operator are placed in the new
+ BASH_REMATCH array variable.
+
+ff. New `failglob' option that causes an expansion error when pathname
+ expansion fails to produce a match.
+
+gg. New `set -o pipefail' option that causes a pipeline to return a failure
+ status if any of the processes in the pipeline fail, not just the last
+ one.
+
+hh. printf builtin understands two new escape sequences: \" and \?.
+
+ii. `echo -e' understands two new escape sequences: \" and \?.
+
+jj. The GNU `gettext' package and libintl have been integrated; the shell's
+ messages can be translated into different languages.
+
+kk. The `\W' prompt expansion now abbreviates $HOME as `~', like `\w'.
+
+ll. The error message printed when bash cannot open a shell script supplied
+ as argument 1 now includes the name of the shell, to better identify
+ the error as coming from bash.
+
+mm. The parameter pattern removal and substitution expansions are now much
+ faster and more efficient when using multibyte characters.
+
+nn. The `jobs', `kill', and `wait' builtins now accept job control notation
+ even if job control is not enabled.
+
+oo. The historical behavior of `trap' that allows a missing `action' argument
+ to cause each specified signal's handling to be reset to its default is
+ now only supported when `trap' is given a single non-option argument.
+
+2. New Features in Readline
+
+a. History expansion has a new `a' modifier equivalent to the `g' modifier
+ for compatibility with the BSD csh.
+
+b. History expansion has a new `G' modifier equivalent to the BSD csh `g'
+ modifier, which performs a substitution once per word.
+
+c. All non-incremental search operations may now undo the operation of
+ replacing the current line with the history line.
+
+d. The text inserted by an `a' command in vi mode can be reinserted with
+ `.'.
+
+e. New bindable variable, `show-all-if-unmodified'. If set, the readline
+ completer will list possible completions immediately if there is more
+ than one completion and partial completion cannot be performed.
+
+f. There is a new application-callable `free_history_entry()' function.
+
+g. History list entries now contain timestamp information; the history file
+ functions know how to read and write timestamp information associated
+ with each entry.
+
+h. Four new key binding functions have been added:
+
+ rl_bind_key_if_unbound()
+ rl_bind_key_if_unbound_in_map()
+ rl_bind_keyseq_if_unbound()
+ rl_bind_keyseq_if_unbound_in_map()
+
+i. New application variable, rl_completion_quote_character, set to any
+ quote character readline finds before it calls the application completion
+ function.
+
+j. New application variable, rl_completion_suppress_quote, settable by an
+ application completion function. If set to non-zero, readline does not
+ attempt to append a closing quote to a completed word.
+
+k. New application variable, rl_completion_found_quote, set to a non-zero
+ value if readline determines that the word to be completed is quoted.
+ Set before readline calls any application completion function.
+
+l. New function hook, rl_completion_word_break_hook, called when readline
+ needs to break a line into words when completion is attempted. Allows
+ the word break characters to vary based on position in the line.
+
+m. New bindable command: unix-filename-rubout. Does the same thing as
+ unix-word-rubout, but adds `/' to the set of word delimiters.
+
+n. When listing completions, directories have a `/' appended if the
+ `mark-directories' option has been enabled.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-2.05b since
+the release of bash-2.05a. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. If set, TMOUT is the default timeout for the `read' builtin.
+
+b. `type' has two new options: `-f' suppresses shell function lookup, and
+ `-P' forces a $PATH search.
+
+c. New code to handle multibyte characters.
+
+d. `select' was changed to be more ksh-compatible, in that the menu is
+ reprinted each time through the loop only if REPLY is set to NULL.
+ The previous behavior is available as a compile-time option.
+
+e. `complete -d' and `complete -o dirnames' now force a slash to be
+ appended to names which are symlinks to directories.
+
+f. There is now a bindable edit-and-execute-command readline command,
+ like the vi-mode `v' command, bound to C-xC-e in emacs mode.
+
+g. Added support for ksh93-like [:word:] character class in pattern matching.
+
+h. The $'...' quoting construct now expands \cX to Control-X.
+
+i. A new \D{...} prompt expansion; passes the `...' to strftime and inserts
+ the result into the expanded prompt.
+
+j. The shell now performs arithmetic in the largest integer size the
+ machine supports (intmax_t), instead of long.
+
+k. If a numeric argument is supplied to one of the bash globbing completion
+ functions, a `*' is appended to the word before expansion is attempted.
+
+l. The bash globbing completion functions now allow completions to be listed
+ with double tabs or if `show-all-if-ambiguous' is set.
+
+m. New `-o nospace' option for `complete' and `compgen' builtins; suppresses
+ readline's appending a space to the completed word.
+
+n. New `here-string' redirection operator: <<< word.
+
+o. When displaying variables, function attributes and definitions are shown
+ separately, allowing them to be re-used as input (attempting to re-use
+ the old output would result in syntax errors).
+
+p. There is a new configuration option `--enable-mem-scramble', controls
+ bash malloc behavior of writing garbage characters into memory at
+ allocation and free time.
+
+q. The `complete' and `compgen' builtins now have a new `-s/-A service'
+ option to complete on names from /etc/services.
+
+r. `read' has a new `-u fd' option to read from a specified file descriptor.
+
+s. Fix the completion code so that expansion errors in a directory name
+ don't cause a longjmp back to the command loop.
+
+t. Fixed word completion inside command substitution to work a little more
+ intuitively.
+
+u. The `printf' %q format specifier now uses $'...' quoting to print the
+ argument if it contains non-printing characters.
+
+v. The `declare' and `typeset' builtins have a new `-t' option. When applied
+ to functions, it causes the DEBUG trap to be inherited by the named
+ function. Currently has no effect on variables.
+
+w. The DEBUG trap is now run *before* simple commands, ((...)) commands,
+ [[...]] conditional commands, and for ((...)) loops.
+
+x. The expansion of $LINENO inside a shell function is only relative to the
+ function start if the shell is interactive -- if the shell is running a
+ script, $LINENO expands to the line number in the script. This is as
+ POSIX-2001 requires.
+
+y. The bash debugger in examples/bashdb has been modified to work with the
+ new DEBUG trap semantics, the command set has been made more gdb-like,
+ and the changes to $LINENO make debugging functions work better. Code
+ from Gary Vaughan.
+
+z. New [n]<&word- and [n]>&word- redirections from ksh93 -- move fds (dup
+ and close).
+
+aa. There is a new `-l' invocation option, equivalent to `--login'.
+
+bb. The `hash' builtin has a new `-l' option to list contents in a reusable
+ format, and a `-d' option to remove a name from the hash table.
+
+cc. There is now support for placing the long help text into separate files
+ installed into ${datadir}/bash. Not enabled by default; can be turned
+ on with `--enable-separate-helpfiles' option to configure.
+
+dd. All builtins that take operands accept a `--' pseudo-option, except
+ `echo'.
+
+ee. The `echo' builtin now accepts \0xxx (zero to three octal digits following
+ the `0') in addition to \xxx (one to three octal digits) for SUSv3/XPG6/
+ POSIX.1-2001 compliance.
+
+
+2. New Features in Readline
+
+a. Support for key `subsequences': allows, e.g., ESC and ESC-a to both
+ be bound to readline functions. Now the arrow keys may be used in vi
+ insert mode.
+
+b. When listing completions, and the number of lines displayed is more than
+ the screen length, readline uses an internal pager to display the results.
+ This is controlled by the `page-completions' variable (default on).
+
+c. New code to handle editing and displaying multibyte characters.
+
+d. The behavior introduced in bash-2.05a of deciding whether or not to
+ append a slash to a completed name that is a symlink to a directory has
+ been made optional, controlled by the `mark-symlinked-directories'
+ variable (default is the 2.05a behavior).
+
+e. The `insert-comment' command now acts as a toggle if given a numeric
+ argument: if the first characters on the line don't specify a
+ comment, insert one; if they do, delete the comment text
+
+f. New application-settable completion variable:
+ rl_completion_mark_symlink_dirs, allows an application's completion
+ function to temporarily override the user's preference for appending
+ slashes to names which are symlinks to directories.
+
+g. New function available to application completion functions:
+ rl_completion_mode, to tell how the completion function was invoked
+ and decide which argument to supply to rl_complete_internal (to list
+ completions, etc.).
+
+h. Readline now has an overwrite mode, toggled by the `overwrite-mode'
+ bindable command, which could be bound to `Insert'.
+
+i. New application-settable completion variable:
+ rl_completion_suppress_append, inhibits appending of
+ rl_completion_append_character to completed words.
+
+j. New key bindings when reading an incremental search string: ^W yanks
+ the currently-matched word out of the current line into the search
+ string; ^Y yanks the rest of the current line into the search string,
+ DEL or ^H deletes characters from the search string.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-2.05a since
+the release of bash-2.05. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. Added support for DESTDIR installation root prefix, so you can do a
+ `make install DESTDIR=bash-root' and do easier binary packaging.
+
+b. Added support for builtin printf "'" flag character as per latest POSIX
+ drafts.
+
+c. Support for POSIX.2 printf(1) length specifiers `j', `t', and `z' (from
+ ISO C99).
+
+d. New autoconf macro, RL_LIB_READLINE_VERSION, for use by other applications
+ (bash doesn't use very much of what it returns).
+
+e. `set [-+]o nolog' is recognized as required by the latest POSIX drafts,
+ but ignored.
+
+f. New read-only `shopt' option: login_shell. Set to non-zero value if the
+ shell is a login shell.
+
+g. New `\A' prompt string escape sequence; expands to time in 24 HH:MM format.
+
+h. New `-A group/-g' option to complete and compgen; does group name
+ completion.
+
+i. New `-t' option to `hash' to list hash values for each filename argument.
+
+j. New [-+]O invocation option to set and unset `shopt' options at startup.
+
+k. configure's `--with-installed-readline' option now takes an optional
+ `=PATH' suffix to set the root of the tree where readline is installed
+ to PATH.
+
+l. The ksh-like `ERR' trap has been added. The `ERR' trap will be run
+ whenever the shell would have exited if the -e option were enabled.
+ It is not inherited by shell functions.
+
+m. `readonly', `export', and `declare' now print variables which have been
+ given attributes but not set by assigning a value as just a command and
+ a variable name (like `export foo') when listing, as the latest POSIX
+ drafts require.
+
+n. `bashbug' now requires that the subject be changed from the default.
+
+o. configure has a new `--enable-largefile' option, like other GNU utilities.
+
+p. `for' loops now allow empty word lists after `in', like the latest POSIX
+ drafts require.
+
+q. The builtin `ulimit' now takes two new non-numeric arguments: `hard',
+ meaning the current hard limit, and `soft', meaning the current soft
+ limit, in addition to `unlimited'
+
+r. `ulimit' now prints the option letter associated with a particular
+ resource when printing more than one limit.
+
+s. `ulimit' prints `hard' or `soft' when a value is not `unlimited' but is
+ one of RLIM_SAVED_MAX or RLIM_SAVED_CUR, respectively.
+
+t. The `printf' builtin now handles the %a and %A conversions if they're
+ implemented by printf(3).
+
+u. The `printf' builtin now handles the %F conversion (just about like %f).
+
+v. The `printf' builtin now handles the %n conversion like printf(3). The
+ corresponding argument is the name of a shell variable to which the
+ value is assigned.
+
+2. New Features in Readline
+
+a. Added extern declaration for rl_get_termcap to readline.h, making it a
+ public function (it was always there, just not in readline.h).
+
+b. New #defines in readline.h: RL_READLINE_VERSION, currently 0x0402,
+ RL_VERSION_MAJOR, currently 4, and RL_VERSION_MINOR, currently 2.
+
+c. New readline variable: rl_readline_version, mirrors RL_READLINE_VERSION.
+
+d. New bindable boolean readline variable: match-hidden-files. Controls
+ completion of files beginning with a `.' (on Unix). Enabled by default.
+
+e. The history expansion code now allows any character to terminate a
+ `:first-' modifier, like csh.
+
+f. New bindable variable `history-preserve-point'. If set, the history
+ code attempts to place the user at the same location on each history
+ line retrieved with previous-history or next-history.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-2.05 since
+the release of bash-2.04. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. Added a new `--init-file' invocation argument as a synonym for `--rcfile',
+ per the new GNU coding standards.
+
+b. The /dev/tcp and /dev/udp redirections now accept service names as well as
+ port numbers.
+
+c. `complete' and `compgen' now take a `-o value' option, which controls some
+ of the aspects of that compspec. Valid values are:
+
+ default - perform bash default completion if programmable
+ completion produces no matches
+ dirnames - perform directory name completion if programmable
+ completion produces no matches
+ filenames - tell readline that the compspec produces filenames,
+ so it can do things like append slashes to
+ directory names and suppress trailing spaces
+
+d. A new loadable builtin, realpath, which canonicalizes and expands symlinks
+ in pathname arguments.
+
+e. When `set' is called without options, it prints function definitions in a
+ way that allows them to be reused as input. This affects `declare' and
+ `declare -p' as well. This only happens when the shell is not in POSIX
+ mode, since POSIX.2 forbids this behavior.
+
+f. Bash-2.05 once again honors the current locale setting when processing
+ ranges within pattern matching bracket expressions (e.g., [A-Z]).
+
+2. New Features in Readline
+
+a. The blink timeout for paren matching is now settable by applications,
+ via the rl_set_paren_blink_timeout() function.
+
+b. _rl_executing_macro has been renamed to rl_executing_macro, which means
+ it's now part of the public interface.
+
+c. Readline has a new variable, rl_readline_state, which is a bitmap that
+ encapsulates the current state of the library; intended for use by
+ callbacks and hook functions.
+
+d. New application-callable function rl_set_prompt(const char *prompt):
+ expands its prompt string argument and sets rl_prompt to the result.
+
+e. New application-callable function rl_set_screen_size(int rows, int cols):
+ public method for applications to set readline's idea of the screen
+ dimensions.
+
+f. New function, rl_get_screen_size (int *rows, int *columns), returns
+ readline's idea of the screen dimensions.
+
+g. The timeout in rl_gather_tyi (readline keyboard input polling function)
+ is now settable via a function (rl_set_keyboard_input_timeout()).
+
+h. Renamed the max_input_history variable to history_max_entries; the old
+ variable is maintained for backwards compatibility.
+
+i. The list of characters that separate words for the history tokenizer is
+ now settable with a variable: history_word_delimiters. The default
+ value is as before.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-2.04 since
+the release of bash-2.03. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. The history builtin has a `-d offset' option to delete the history entry
+ at position `offset'.
+
+b. The prompt expansion code has two new escape sequences: \j, the number of
+ active jobs; and \l, the basename of the shell's tty device name.
+
+c. The `bind' builtin has a new `-x' option to bind key sequences to shell
+ commands.
+
+d. There is a new shell option, no_empty_command_completion, which, when
+ enabled, disables command completion when TAB is typed on an empty line.
+
+e. The `help' builtin has a `-s' option to just print a builtin's usage
+ synopsis.
+
+f. There are several new arithmetic operators: id++, id-- (variable
+ post-increment/decrement), ++id, --id (variable pre-increment/decrement),
+ expr1 , expr2 (comma operator).
+
+g. There is a new ksh-93 style arithmetic for command:
+ for ((expr1 ; expr2; expr3 )); do list; done
+
+h. The `read' builtin has a number of new options:
+ -t timeout only wait timeout seconds for input
+ -n nchars only read nchars from input instead of a full line
+ -d delim read until delim rather than newline
+ -s don't echo input chars as they are read
+
+i. The redirection code now handles several filenames specially:
+ /dev/fd/N, /dev/stdin, /dev/stdout, and /dev/stderr, whether or
+ not they are present in the file system.
+
+j. The redirection code now recognizes pathnames of the form
+ /dev/tcp/host/port and /dev/udp/host/port, and tries to open a socket
+ of the appropriate type to the specified port on the specified host.
+
+k. The ksh-93 ${!prefix*} expansion, which expands to the names of all
+ shell variables with prefix PREFIX, has been implemented.
+
+l. There is a new dynamic variable, FUNCNAME, which expands to the name of
+ a currently-executing function. Assignments to FUNCNAME have no effect.
+
+m. The GROUPS variable is no longer readonly; assignments to it are silently
+ discarded. This means it can be unset.
+
+n. A new programmable completion facility, with two new builtin commands:
+ complete and compgen.
+
+o. configure has a new option, `--enable-progcomp', to compile in the
+ programmable completion features (enabled by default).
+
+p. `shopt' has a new option, `progcomp', to enable and disable programmable
+ completion at runtime.
+
+q. Unsetting HOSTFILE now clears the list of hostnames used for completion.
+
+r. configure has a new option, `--enable-bash-malloc', replacing the old
+ `--with-gnu-malloc' (which is still present for backwards compatibility).
+
+s. There is a new manual page describing rbash, the restricted shell.
+
+t. `bashbug' has new `--help' and `--version' options.
+
+u. `shopt' has a new `xpg_echo' option, which controls the behavior of
+ `echo' with respect to backslash-escaped characters at runtime.
+
+v. If NON_INTERACTIVE_LOGIN_SHELLS is defined, all login shells read the
+ startup files, even if they are not interactive.
+
+w. The LC_NUMERIC variable is now treated specially, and used to set the
+ LC_NUMERIC locale category for number formatting, e.g., when `printf'
+ displays floating-point numbers.
+
+2. New features in Readline
+
+a. Parentheses matching is now always compiled into readline, and enabled
+ or disabled when the value of the `blink-matching-paren' variable is
+ changed.
+
+b. MS-DOS systems now use ~/_inputrc as the last-ditch inputrc filename.
+
+c. MS-DOS systems now use ~/_history as the default history file.
+
+d. history-search-{forward,backward} now leave the point at the end of the
+ line when the string to search for is empty, like
+ {reverse,forward}-search-history.
+
+e. history-search-{forward,backward} now leave the last history line found
+ in the readline buffer if the second or subsequent search fails.
+
+f. New function for use by applications: rl_on_new_line_with_prompt, used
+ when an application displays the prompt itself before calling readline().
+
+g. New variable for use by applications: rl_already_prompted. An application
+ that displays the prompt itself before calling readline() must set this to
+ a non-zero value.
+
+h. A new variable, rl_gnu_readline_p, always 1. The intent is that an
+ application can verify whether or not it is linked with the `real'
+ readline library or some substitute.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-2.03 since
+the release of bash-2.02. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. New `shopt' option, `restricted_shell', indicating whether or not the
+ shell was started in restricted mode, for use in startup files.
+
+b. Filename generation is now performed on the words between ( and ) in
+ array assignments (which it probably should have done all along).
+
+c. OLDPWD is now auto-exported, as POSIX.2 seems to require.
+
+d. ENV and BASH_ENV are read-only variables in a restricted shell.
+
+e. A change was made to the startup file code so that any shell begun with
+ the `--login' option, even non-interactive shells, will source the login
+ shell startup files.
+
+2. New Features in Readline
+
+a. Many changes to the signal handling:
+ o Readline now catches SIGQUIT and cleans up the tty before returning;
+ o A new variable, rl_catch_signals, is available to application writers
+ to indicate to readline whether or not it should install its own
+ signal handlers for SIGINT, SIGTERM, SIGQUIT, SIGALRM, SIGTSTP,
+ SIGTTIN, and SIGTTOU;
+ o A new variable, rl_catch_sigwinch, is available to application
+ writers to indicate to readline whether or not it should install its
+ own signal handler for SIGWINCH, which will chain to the calling
+ applications's SIGWINCH handler, if one is installed;
+ o There is a new function, rl_free_line_state, for application signal
+ handlers to call to free up the state associated with the current
+ line after receiving a signal;
+ o There is a new function, rl_cleanup_after_signal, to clean up the
+ display and terminal state after receiving a signal;
+ o There is a new function, rl_reset_after_signal, to reinitialize the
+ terminal and display state after an application signal handler
+ returns and readline continues
+
+b. There is a new function, rl_resize_terminal, to reset readline's idea of
+ the screen size after a SIGWINCH.
+
+c. New public functions: rl_save_prompt and rl_restore_prompt. These were
+ previously private functions with a `_' prefix.
+
+d. New function hook: rl_pre_input_hook, called just before readline starts
+ reading input, after initialization.
+
+e. New function hook: rl_display_matches_hook, called when readline would
+ display the list of completion matches. The new function
+ rl_display_match_list is what readline uses internally, and is available
+ for use by application functions called via this hook.
+
+f. New bindable function, delete-char-or-list, like tcsh.
+
+g. A new variable, rl_erase_empty_line, which, if set by an application using
+ readline, will cause readline to erase, prompt and all, lines on which the
+ only thing typed was a newline.
+
+h. New bindable variable: `isearch-terminators'.
+
+i. New bindable function: `forward-backward-delete-char' (unbound by default).
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-2.02 since
+the release of bash-2.01.1. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. A new version of malloc, based on the older GNU malloc, that has many
+ changes, is more page-based, is more conservative with memory usage,
+ and does not `orphan' large blocks when they are freed.
+
+b. A new version of gmalloc, based on the old GLIBC malloc, with many
+ changes and range checking included by default.
+
+c. A new implementation of fnmatch(3) that includes full POSIX.2 Basic
+ Regular Expression matching, including character classes, collating
+ symbols, equivalence classes, and support for case-insensitive pattern
+ matching.
+
+d. ksh-88 egrep-style extended pattern matching ([@+*?!](patlist)) has been
+ implemented, controlled by a new `shopt' option, `extglob'.
+
+e. There is a new ksh-like `[[' compound command, which implements
+ extended `test' functionality.
+
+f. There is a new `printf' builtin, implemented according to the POSIX.2
+ specification.
+
+g. There is a new feature for command substitution: $(< filename) now expands
+ to the contents of `filename', with any trailing newlines removed
+ (equivalent to $(cat filename)).
+
+h. There are new tilde prefixes which expand to directories from the
+ directory stack.
+
+i. There is a new `**' arithmetic operator to do exponentiation.
+
+j. There are new configuration options to control how bash is linked:
+ `--enable-profiling', to allow bash to be profiled with gprof, and
+ `--enable-static-link', to allow bash to be linked statically.
+
+k. There is a new configuration option, `--enable-cond-command', which
+ controls whether or not the `[[' command is included. It is on by
+ default.
+
+l. There is a new configuration option, `--enable-extended-glob', which
+ controls whether or not the ksh extended globbing feature is included.
+ It is enabled by default.
+
+m. There is a new configuration #define in config.h.top that, when enabled,
+ will cause all login shells to source /etc/profile and one of the user-
+ specific login shell startup files, whether or not the shell is
+ interactive.
+
+n. There is a new invocation option, `--dump-po-strings', to dump
+ a shell script's translatable strings ($"...") in GNU `po' format.
+
+o. There is a new `shopt' option, `nocaseglob', to enable case-insensitive
+ pattern matching when globbing filenames and using the `case' construct.
+
+p. There is a new `shopt' option, `huponexit', which, when enabled, causes
+ the shell to send SIGHUP to all jobs when an interactive login shell
+ exits.
+
+q. `bind' has a new `-u' option, which takes a readline function name as an
+ argument and unbinds all key sequences bound to that function in a
+ specified keymap.
+
+r. `disown' now has `-a' and `-r' options, to limit operation to all jobs
+ and running jobs, respectively.
+
+s. The `shopt' `-p' option now causes output to be displayed in a reusable
+ format.
+
+t. `test' has a new `-N' option, which returns true if the filename argument
+ has been modified since it was last accessed.
+
+u. `umask' now has a `-p' option to print output in a reusable format.
+
+v. A new escape sequence, `\xNNN', has been added to the `echo -e' and $'...'
+ translation code. It expands to the character whose ascii code is NNN
+ in hexadecimal.
+
+w. The prompt string expansion code has a new `\r' escape sequence.
+
+x. The shell may now be cross-compiled for the CYGWIN32 environment on
+ a Unix machine.
+
+2. New Features in Readline
+
+a. There is now an option for `iterative' yank-last-arg handline, so a user
+ can keep entering `M-.', yanking the last argument of successive history
+ lines.
+
+b. New variable, `print-completions-horizontally', which causes completion
+ matches to be displayed across the screen (like `ls -x') rather than up
+ and down the screen (like `ls').
+
+c. New variable, `completion-ignore-case', which causes filename completion
+ and matching to be performed case-insensitively.
+
+d. There is a new bindable command, `magic-space', which causes history
+ expansion to be performed on the current readline buffer and a space to
+ be inserted into the result.
+
+e. There is a new bindable command, `menu-complete', which enables tcsh-like
+ menu completion (successive executions of menu-complete insert a single
+ completion match, cycling through the list of possible completions).
+
+f. There is a new bindable command, `paste-from-clipboard', for use on Win32
+ systems, to insert the text from the Win32 clipboard into the editing
+ buffer.
+
+g. The key sequence translation code now understands printf-style backslash
+ escape sequences, including \NNN octal escapes. These escape sequences
+ may be used in key sequence definitions or macro values.
+
+h. An `$include' inputrc file parser directive has been added.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-2.01 since
+the release of bash-2.0. As always, the manual page (doc/bash.1) is the
+place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. There is a new builtin array variable: GROUPS, the set of groups to which
+ the user belongs. This is used by the test suite.
+
+2. New Features in Readline
+
+a. If a key sequence bound to `universal-argument' is read while reading a
+ numeric argument started with `universal-argument', it terminates the
+ argument but is otherwise ignored. This provides a way to insert multiple
+ instances of a digit string, and is how GNU emacs does it.
+
+-------------------------------------------------------------------------------
+This is a terse description of the new features added to bash-2.0 since
+the release of bash-1.14.7. As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. There is a new invocation option, -D, that dumps translatable strings
+ in a script.
+
+b. The `long' invocation options must now be prefixed with `--'.
+
+c. New long invocation options: --dump-strings, --help, --verbose
+
+d. The `nolineediting' invocation option was renamed to `noediting'.
+
+e. The `nobraceexpansion' and `quiet' long invocation options were removed.
+
+f. The `--help' and `--version' long options now work as the GNU coding
+ standards specify.
+
+g. If invoked as `sh', bash now enters posix mode after reading the
+ startup files, and reads and executes commands from the file named
+ by $ENV if interactive (as POSIX.2 specifies). A login shell invoked
+ as `sh' reads $ENV after /etc/profile and ~/.profile.
+
+h. There is a new reserved word, `time', for timing pipelines, builtin
+ commands, and shell functions. It uses the value of the TIMEFORMAT
+ variable as a format string describing how to print the timing
+ statistics.
+
+i. The $'...' quoting syntax expands ANSI-C escapes in ... and leaves the
+ result single-quoted.
+
+j. The $"..." quoting syntax performs locale-specific translation of ...
+ and leaves the result double-quoted.
+
+k. LINENO now works correctly in functions.
+
+l. New variables: DIRSTACK, PIPESTATUS, BASH_VERSINFO, HOSTNAME, SHELLOPTS,
+ MACHTYPE. The first three are array variables.
+
+m. The BASH_VERSION and BASH_VERSINFO variables now include the shell's
+ `release status' (alpha[N], beta[N], release).
+
+n. Some variables have been removed: MAIL_WARNING, notify, history_control,
+ command_oriented_history, glob_dot_filenames, allow_null_glob_expansion,
+ nolinks, hostname_completion_file, noclobber, no_exit_on_failed_exec, and
+ cdable_vars. Most of them are now implemented with the new `shopt'
+ builtin; others were already implemented by `set'.
+
+o. Bash now uses some new variables: LC_ALL, LC_MESSAGES, LC_CTYPE,
+ LC_COLLATE, LANG, GLOBIGNORE, HISTIGNORE.
+
+p. The shell now supports integer-indexed arrays of unlimited length,
+ with a new compound assignment syntax and changes to the appropriate
+ builtin commands (declare/typeset, read, readonly, etc.). The array
+ index may be an arithmetic expression.
+
+q. ${!var}: indirect variable expansion, equivalent to eval \${$var}.
+
+r. ${parameter:offset[:length]}: variable substring extraction.
+
+s. ${parameter/pattern[/[/]string]}: variable pattern substitution.
+
+t. The $[...] arithmetic expansion syntax is no longer supported, in
+ favor of $((...)).
+
+u. Aliases can now be expanded in shell scripts with a shell option
+ (shopt expand_aliases).
+
+v. History and history expansion can now be used in scripts with
+ set -o history and set -H.
+
+w. All builtins now return an exit status of 2 for incorrect usage.
+
+x. Interactive shells resend SIGHUP to all running or stopped children
+ if (and only if) they exit due to a SIGHUP.
+
+y. New prompting expansions: \a, \e, \H, \T, \@, \v, \V.
+
+z. Variable expansion in prompt strings is now controllable via a shell
+ option (shopt promptvars).
+
+aa. Bash now defaults to using command-oriented history.
+
+bb. The history file ($HISTFILE) is now truncated to $HISTFILESIZE after
+ being written.
+
+cc. The POSIX.2 conditional arithmetic evaluation syntax (expr ? expr : expr)
+ has been implemented.
+
+dd. Each builtin now accepts `--' to signify the end of the options, except
+ as documented (echo, etc.).
+
+ee. All builtins use -p to display values in a re-readable format where
+ appropriate, except as documented (echo, type, etc.).
+
+ff. The `alias' builtin has a new -p option.
+
+gg. Changes to the `bind' builtin:
+ o has new options: -psPSVr.
+ o the `-d' option was renamed to `-p'
+ o the `-v' option now dumps variables; the old `-v' is now `-P'
+
+hh. The `bye' synonym for `exit' was removed.
+
+ii. The -L and -P options to `cd' and `pwd' have been documented.
+
+jj. The `cd' builtin now does spelling correction on the directory name
+ by default. This is settable with a shell option (shopt cdspell).
+
+kk. The `declare' builtin has new options: -a, -F, -p.
+
+ll. The `dirs' builtin has new options: -c, -p, -v.
+
+mm. The new `disown' builtin removes jobs from the shell's jobs table
+ or inhibits the resending of SIGHUP when the shell receives a
+ SIGHUP.
+
+nn. The `echo' builtin has a new escape character: \e.
+
+oo. The `enable' builtin can now load new builtins dynamically from shared
+ objects on systems with the dlopen/dlsym interface. There are a number
+ of examples in the examples/loadables directory. There are also
+ new options: -d, -f, -s, -p.
+
+pp. The `-all' option to `enable' was removed in favor of `-a'.
+
+qq. The `exec' builtin has new options: -l, -c, -a.
+
+rr. The `hash' builtin has a new option: -p.
+
+ss. The `history' builtin has new options: -c, -p, -s.
+
+tt. The `jobs' builtin has new options: -r, -s.
+
+uu. The `kill' builtin has new options: -n signum, -l signame.
+
+vv. The `pushd' and `popd' builtins have a new option: -n.
+
+ww. The `read' builtin has new options: -p prompt, -e, -a.
+
+xx. The `readonly' builtin has a new -a option, and the -n option was removed.
+
+yy. Changes to the `set' builtin:
+ o new options: -B, -o keyword, -o onecmd, -o history
+ o options removed: -l, -d, -o nohash
+ o options changed: +o, -h, -o hashall
+ o now displays variables in a format that can be re-read as input
+
+zz. The new `shopt' builtin controls shell optional behavior previously
+ done by setting and unsetting certain shell variables.
+
+aaa. The `test' builtin has new operators: -o option, s1 == s2, s1 < s2,
+ and s1 > s2, where s1 and s2 are strings.
+
+bbb. There is a new trap, DEBUG, executed after every simple command.
+
+ccc. The `trap' builtin has a new -p option.
+
+ddd. The `ulimit' builtin has a new -l option on 4.4BSD-based systems.
+
+eee. The PS1, PS2, PATH, and IFS variables may now be unset.
+
+fff. The restricted shell mode has been expanded and is now documented.
+
+ggg. Security improvements:
+ o functions are not imported from the environment if running setuid
+ or with -p
+ o no startup files are sourced if running setuid or with -p
+
+hhh. The documentation has been overhauled: the texinfo manual was
+ expanded, and HTML versions of the man page and texinfo manual
+ are included.
+
+iii. Changes to Posix mode:
+ o Command lookup now finds special builtins before shell functions.
+ o Failure of a special builtin causes a non-interactive shell to
+ exit. Failures are defined in the POSIX.2 specification.
+ o If the `cd' builtin finds a directory to change to using $CDPATH,
+ the value assigned to PWD when `cd' completes does not contain
+ any symbolic links.
+ o A non-interactive shell exits if a variable assignment error
+ occurs when no command name follows the assignment statements.
+ o A non-interactive shell exits if the iteration variable in a
+ `for' statement or the selection variable in a `select' statement
+ is read-only or another variable assignment error occurs.
+ o The `<>' redirection operator now opens a file for both stdin and
+ stdout by default, not just when in posix mode.
+ o Assignment statements preceding special builtins now persist in
+ the shell's environment when the builtin completes.
+
+ Posix mode is now completely POSIX.2-compliant (modulo bugs). When
+ invoked as sh, bash should be completely POSIX.2-compliant.
+
+jjj. The default value of PS1 is now "\s-\v\$ ".
+
+kkk. The ksh-like ((...)) arithmetic command syntax has been implemented.
+ This is exactly equivalent to `let "..."'.
+
+lll. Integer constants have been extended to base 64.
+
+mmm. The `ulimit' builtin now sets both hard and soft limits and reports the
+ soft limit by default.
+
+2. New Features in Readline
+
+a. New variables: enable-keypad, input-meta (new name for meta-flag),
+ mark-directories, visible-stats (now documented), disable-completion,
+ comment-begin.
+
+b. New bindable commands: kill-region, copy-region-as-kill,
+ copy-backward-word, copy-forward-word, set-mark, exchange-point-and-mark,
+ character-search, character-search-backward, insert-comment,
+ glob-expand-word, glob-list-expansions, dump-variables, dump-macros.
+
+c. New emacs keybindings: delete-horizontal-space (M-\),
+ insert-completions (M-*), possible-completions (M-=).
+
+d. The history-search-backward and history-search-forward commands were
+ modified to be the same as previous-line and next-line if point is at
+ the start of the line.
+
+e. More file types are available for the visible-stats mode.
+
+3. Changes of interest in the Bash implementation
+
+a. There is a new autoconf-based configuration mechanism.
+
+b. More things have been moved from Posix mode to standard shell behavior.
+
+c. The trace output (set -x) now inserts quotes where necessary so it can
+ be reused as input.
+
+d. There is a compile-time option for a system-wide interactive shell
+ startup file (disabled by default).
+
+e. The YACC grammar is smaller and tighter, and all 66 shift-reduce
+ conflicts are gone. Several parsing bugs have been fixed.
+
+f. Builtin option parsing has been regularized (using internal_getopt()),
+ with the exception of `echo', `type', and `set'.
+
+g. Builtins now return standard usage messages constructed from the
+ `short doc' used by the help builtin.
+
+h. Completion now quotes using backslashes by default, but honors
+ user-supplied quotes.
+
+i. The GNU libc malloc is available as a configure-time option.
+
+j. There are more internationalization features; bash uses gettext if
+ it is available. The $"..." translation syntax uses the current
+ locale and gettext.
+
+k. There is better reporting of job termination when the shell is not
+ interactive.
+
+l. The shell is somewhat more efficient: it uses a little less memory and
+ makes fewer system calls.
+
+4. Changes of interest in the Readline implementation
+
+a. There is now support for readline `callback' functions.
+
+b. There is now support for user-supplied input, redisplay, and terminal
+ preparation functions.
+
+c. Most of the shell-specific code in readline has been generalized or
+ removed.
+
+d. Most of the annoying redisplay bugs have been fixed, notably the problems
+ with incremental search and excessive redrawing when special characters
+ appear in the prompt string.
+
+e. There are new library functions and variables available to application
+ writers, most having to do with completion and quoting.
+
+f. The NEWLINE character (^J) is now treated as a search terminator by the
+ incremental search functions.
+-------------------------------------------------------------------------------
+
+Copying and distribution of this file, with or without modification,
+are permitted in any medium without royalty provided the copyright
+notice and this notice are preserved. This file is offered as-is,
+without any warranty.