Bash 4.0 liberada
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+========== NEWS ==========+
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.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
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