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 mechansim 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.

