news

android-w.song.android.widget

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.