#4404: bash-5.0
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Reporter: avmaisak | Owner: lfs-book
Type: task | Status: new
Priority: normal | Milestone: 8.4
Component: Book | Version: SVN
Severity: normal | Resolution:
Keywords: |
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Comment (by bdubbs):
This is a terse description of the new features added to bash-5.0 since
the release of bash-4.4. As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.
1. New Features in Bash
a. The `wait' builtin can now wait for the last process substitution
created.
b. There is an EPOCHSECONDS variable, which expands to the time in seconds
since the Unix epoch.
c. There is an EPOCHREALTIME variable, which expands to the time in
seconds
since the Unix epoch with microsecond granularity.
d. New loadable builtins: rm, stat, fdflags.
e. BASH_ARGV0: a new variable that expands to $0 and sets $0 on
assignment.
f. When supplied a numeric argument, the shell-expand-line bindable
readline
command does not perform quote removal and suppresses command and
process
substitution.
g. `history -d' understands negative arguments: negative arguments offset
from
the end of the history list.
h. The `name' argument to the `coproc' reserved word now undergoes word
expansion, so unique coprocs can be created in loops.
i. A nameref name resolution loop in a function now resolves to a variable
by
that name in the global scope.
j. The `wait' builtin now has a `-f' option, which signfies to wait until
the
specified job or process terminates, instead of waiting until it
changes
state.
k. There is a define in config-top.h that allows the shell to use a static
value for $PATH, overriding whatever is in the environment at startup,
for
use by the restricted shell.
l. Process substitution does not inherit the `v' option, like command
substitution.
m. If a non-interactive shell with job control enabled detects that a
foreground
job died due to SIGINT, it acts as if it received the SIGINT.
n. The SIGCHLD trap is run once for each exiting child process even if job
control is not enabled when the shell is in Posix mode.
o. A new shopt option: localvar_inherit; if set, a local variable inherits
the
value of a variable with the same name at the nearest preceding scope.
p. `bind -r' now checks whether a key sequence is bound before binding it
to
NULL, to avoid creating keymaps for a multi-key sequence.
q. A numeric argument to the line editing `operate-and-get-next' command
specifies which history entry to use.
r. The positional parameters are now assigned before running the shell
startup
files, so startup files can use $@.
s. There is a compile-time option that forces the shell to disable the
check
for an inherited OLDPWD being a directory.
t. The `history' builtin can now delete ranges of history entries using
`-d start-end'.
u. The `vi-edit-and-execute-command' bindable readline command now puts
readline
back in vi insertion mode after executing commands from the edited
file.
v. The command completion code now matches aliases and shell function
names
case-insensitively if the readline completion-ignore-case variable is
set.
w. There is a new `assoc_expand_once' shell option that attempts to expand
associative array subscripts only once.
x. The shell only sets up BASH_ARGV and BASH_ARGC at startup if extended
debugging mode is active. The old behavior of unconditionally setting
them
is available as part of the shell compatibility options.
y. The `umask' builtin now allows modes and masks greater than octal 777.
z. The `times' builtin now honors the current locale when printing a
decimal
point.
aa. There is a new (disabled by default, undocumented) shell option to
enable
and disable sending history to syslog at runtime.
bb. Bash no longer allows variable assignments preceding a special builtin
that
changes variable attributes to propagate back to the calling
environment
unless the compatibility level is 44 or lower.
cc. You can set the default value for $HISTSIZE at build time in config-
top.h.
dd. The `complete' builtin now accepts a -I option that applies the
completion
to the initial word on the line.
ee. The internal bash malloc now uses mmap (if available) to satisfy
requests
greater than 128K bytes, so free can use mfree to return the pages to
the
kernel.
ff. The shell doesn't automatically set BASH_ARGC and BASH_ARGV at startup
unless it's in debugging mode, as the documentation has always said,
but
will dynamically create them if a script references them at the top
level
without having enabled debugging mode.
gg. The localvar_inherit option will not attempt to inherit a value from a
variable of an incompatible type (indexed vs. associative arrays, for
example).
hh. The `globasciiranges' option is now enabled by default; it can be set
to
off by default at configuration time.
ii. Associative and indexed arrays now allow subscripts consisting solely
of
whitespace.
jj. `checkwinsize' is now enabled by default.
kk. The `localvar_unset' shopt option is now visible and documented.
ll. The `progcomp_alias' shopt option is now visible and documented.
mm. The signal name processing code now understands `SIGRTMIN+n' all the
way
up to SIGRTMAX.
nn. There is a new `seq' loadable builtin.
oo. Trap execution now honors the (internal) max invocations of `eval',
since
traps are supposed to be executed as if using `eval'.
pp. The $_ variable doesn't change when the shell executes a command that
forks.
qq. The `kill' builtin now supports -sSIGNAME and -nSIGNUM, even though
conforming applications aren't supposed to use them.
rr. POSIX mode now enables the `shift_verbose' option.
2. New Features in Readline
a. Non-incremental vi-mode search (`N', `n') can search for a shell
pattern, as
Posix specifies (uses fnmatch(3) if available).
b. There are new `next-screen-line' and `previous-screen-line' bindable
commands, which move the cursor to the same column in the next, or
previous,
physical line, respectively.
c. There are default key bindings for control-arrow-key key combinations.
d. A negative argument (-N) to `quoted-insert' means to insert the next N
characters using quoted-insert.
e. New public function: rl_check_signals(), which allows applications to
respond to signals that readline catches while waiting for input using
a custom read function.
f. There is new support for conditionally testing the readline version in
an
inputrc file, with a full set of arithmetic comparison operators
available.
g. There is a simple variable comparison facility available for use within
an
inputrc file. Allowable operators are equality and inequality; string
variables may be compared to a value; boolean variables must be
compared to
either `on' or `off'; variable names are separated from the operator by
whitespace.
h. The history expansion library now understands command and process
substitution and extended globbing and allows them to appear anywhere
in a
word.
i. The history library has a new variable that allows applications to set
the
initial quoting state, so quoting state can be inherited from a
previous
line.
j. Readline now allows application-defined keymap names; there is a new
public
function, rl_set_keymap_name(), to do that.
k. The "Insert" keypad key, if available, now puts readline into overwrite
mode.
--
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