This is a terse description of the new features added to bash-5.2 since
the release of bash-5.1.  As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.

1. New Features in Bash

a. The bash malloc returns memory that is aligned on 16-byte boundaries.

b. There is a new internal timer framework used for read builtin timeouts.

c. Rewrote the command substitution parsing code to call the parser recursively
   and rebuild the command string from the parsed command. This allows better
   syntax checking and catches errors much earlier. Along with this, if
   command substitution parsing completes with here-documents remaining to be
   read, the shell prints a warning message and reads the here-document bodies
   from the current input stream.

d. The `ulimit' builtin now treats an operand remaining after all of the options
   and arguments are parsed as an argument to the last command specified by
   an option. This is for POSIX compatibility.

e. Here-document parsing now handles $'...' and $"..." quoting when reading the
   here-document body.

f. The `shell-expand-line' and `history-and-alias-expand-line' bindable readline
   commands now understand $'...' and $"..." quoting.

g. There is a new `spell-correct-word' bindable readline command to perform
   spelling correction on the current word.

h. The `unset' builtin now attempts to treat arguments as array subscripts
   without parsing or expanding the subscript, even when `assoc_expand_once'
   is not set.

i. There is a default value for $BASH_LOADABLES_PATH in config-top.h.

j. Associative array assignment and certain instances of referencing (e.g.,
   `test -v' now allow `@' and `*' to be used as keys.

k. Bash attempts to expand indexed array subscripts only once when executing
   shell constructs and word expansions.

l. The `unset' builtin allows a subscript of `@' or `*' to unset a key with
   that value for associative arrays instead of unsetting the entire array
   (which you can still do with `unset arrayname'). For indexed arrays, it
   removes all elements of the array without unsetting it (like `A=()').

m. Additional builtins (printf/test/read/wait) do a better job of not
   parsing array subscripts if array_expand_once is set.

n. New READLINE_ARGUMENT variable set to numeric argument for readline commands
   defined using `bind -x'.

o. The new `varredir_close' shell option causes bash to automatically close
   file descriptors opened with {var}<fn and other styles of varassign
   redirection unless they're arguments to the `exec' builtin.

p. The `$0' special parameter is now set to the name of the script when running
   any (non-interactive) startup files such as $BASH_ENV.

q. The `enable' builtin tries to load a loadable builtin using the default
   search path if `enable name' (without any options) attempts to enable a
   non-existent builtin.

r. The `printf' builtin has a new format specifier: %Q. This acts like %q but
   applies any specified precision to the original unquoted argument, then
   quotes and outputs the result.

s. The new `noexpand_translations' option controls whether or not the translated
   output of $"..." is single-quoted.

t. There is a new parameter transformation operator: @k. This is like @K, but
   expands the result to separate words after word splitting.

u. There is an alternate array implementation, selectable at `configure' time,
   that optimizes access speed over memory use (use the new configure
    --enable-alt-array-implementation option).

v. If an [N]<&WORD- or [N]>&WORD- redirection has WORD expand to the empty
   string, treat the redirection as [N]<&- or [N]>&- and close file descriptor
   N (default 0).

w. Invalid parameter transformation operators are now invalid word expansions,
   and so cause fatal errors in non-interactive shells.

x. New shell option: patsub_replacement. When enabled, a `&' in the replacement
   string of the pattern substitution expansion is replaced by the portion of
   the string that matched the pattern. Backslash will escape the `&' and
   insert a literal `&'.

y. `command -p' no longer looks in the hash table for the specified command.

z. The new `--enable-translatable-strings' option to `configure' allows $"..."
   support to be compiled in or out.

aa. The new `globskipdots' shell option forces pathname expansion never to
    return `.' or `..' unless explicitly matched. It is enabled by default.

bb. Array references using `@' and `*' that are the value of nameref variables
    (declare -n ref='v[@]' ; echo $ref) no longer cause the shell to exit if
    set -u is enabled and the array (v) is unset.

cc. There is a new bindable readline command name:
    `vi-edit-and-execute-command'.

dd. In posix mode, the `printf' builtin checks for the `L' length modifier and
    uses long double for floating point conversion specifiers if it's present,
    double otherwise.

ee. The `globbing' completion code now takes the `globstar' option into account.

ff. `suspend -f' now forces the shell to suspend even if job control is not
   currently enabled.

gg. Since there is no `declare -' equivalent of `local -', make sure to use
    `local -' in the output of `local -p'.

2. New Features in Readline

a. There is now an HS_HISTORY_VERSION containing the version number of the
   history library for applications to use.

b. History expansion better understands multiple history expansions that may
   contain strings that would ordinarily inhibit history expansion (e.g.,
   `abc!$!$').

c. There is a new framework for readline timeouts, including new public
   functions to set timeouts and query how much time is remaining before a
   timeout hits, and a hook function that can trigger when readline times
   out. There is a new state value to indicate a timeout.

d. Automatically bind termcap key sequences for page-up and page-down to
   history-search-backward and history-search-forward, respectively.

e. There is a new `fetch-history' bindable command that retrieves the history
   entry corresponding to its numeric argument. Negative arguments count back
   from the end of the history.

f. `vi-undo' is now a bindable command.

g. There is a new option: `enable-active-region'. This separates control of
   the active region and bracketed-paste. It has the same default value as
   bracketed-paste, and enabling bracketed paste enables the active region.
   Users can now turn off the active region while leaving bracketed paste
   enabled.

h. rl_completer_word_break_characters is now `const char *' like
   rl_basic_word_break_characters.

i. Readline looks in $LS_COLORS for a custom filename extension
   (*.readline-colored-completion-prefix) and uses that as the default color
   for the common prefix displayed when `colored-completion-prefix' is set.

j. Two new bindable string variables: active-region-start-color and
   active-region-end-color. The first sets the color used to display the
   active region; the second turns it off. If set, these are used in place
   of terminal standout mode.

k. New readline state (RL_STATE_EOF) and application-visible variable
   (rl_eof_found) to allow applications to detect when readline reads EOF
   before calling the deprep-terminal hook.

l. There is a new configuration option: --with-shared-termcap-library, which
   forces linking the shared readline library with the shared termcap (or
   curses/ncurses/termlib) library so applications don't have to do it.

m. Readline now checks for changes to locale settings (LC_ALL/LC_CTYPE/LANG)
   each time it is called, and modifies the appropriate locale-specific display
   and key binding variables when the locale changes.

-------------------------------------------------------------------------------
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
