Imported from ../bash-2.05b.tar.gz.

[thirdparty/bash.git] / NEWS

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 retrived 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 defintions 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.  ${paramter: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 interation 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.