commit bash-20200520 snapshot

NEWS

@@ -1,3 +1,164 @@
+This is a terse description of the new features added to bash-5.1 since
+the release of bash-5.0.  As always, the manual page (doc/bash.1) is
+the place to look for complete descriptions.
+
+1. New Features in Bash
+
+a. `bind -x' now supports different bindings for different editing modes and
+   keymaps.
+
+b. Bash attempts to optimize the number of times it forks when executing
+   commands in subshells and from `bash -c'.
+
+c. Here documents and here strings now use pipes for the expanded document if
+   it's smaller than the pipe buffer size, reverting to temporary files if it's
+   larger.
+
+d. There are new loadable builtins: mktemp, accept, mkfifo, csv, cut/lcut
+
+e. In posix mode, `trap -p' now displays signals whose disposition is SIG_DFL
+   and those that were SIG_IGN when the shell starts.
+
+f. The shell now expands the history number (e.g., in PS1) even if it is not
+   currently saving commands to the history list.
+
+g. `read -e' may now be used with arbitrary file descriptors (`read -u N').
+
+h. The `select' builtin now runs traps if its internal call to the read builtin
+   is interrupted by a signal.
+
+i. SRANDOM: a new variable that expands to a 32-bit random number that is not
+   produced by an LCRNG, and uses getrandom/getentropy, falling back to
+   /dev/urandom or arc4random if available. There is a fallback generator if
+   none of these are available.
+
+j. shell-transpose-words: a new bindable readline command that uses the same
+   definition of word as shell-forward-word, etc.
+
+k. The shell now adds default bindings for shell-forward-word,
+   shell-backward-word, shell-transpose-words, and shell-kill-word.
+
+l. Bash now allows ARGV0 appearing in the initial shell environment to set $0.
+
+m. If `unset' is executed without option arguments, bash tries to unset a shell
+   function if a name argument cannot be a shell variable name because it's not
+   an identifier.
+
+n. The `test -N' operator uses nanosecond timestamp granularity if it's
+   available.
+
+o. Bash posix mode now treats assignment statements preceding shell function
+   definitions the same as in its default mode, since POSIX has changed and
+   no longer requires those assignments to persist after the function returns
+   (POSIX interp 654).
+
+p. BASH_REMATCH is no longer readonly.
+
+q. wait: has a new -p VARNAME option, which stores the PID returned by `wait -n'
+   or `wait' without arguments.
+
+r. Sorting the results of pathname expansion now uses byte-by-byte comparisons
+   if two strings collate equally to impose a total order; the result of a
+   POSIX interpretation.
+
+s. Bash now allows SIGINT trap handlers to execute recursively.
+
+t. Bash now saves and restores state around setting and unsetting posix mode,
+   instead of having unsetting posix mode set a known state.
+
+u. Process substitution is now available in posix mode.
+
+v. READLINE_MARK: a new variable available while executing commands bound with
+   `bind -x', contains the value of the mark.
+
+w. Bash removes SIGCHLD from the set of blocked signals if it's blocked at shell
+   startup.
+
+x. `test -v N' can now test whether or not positional parameter N is set.
+
+y. `local' now honors the `-p' option to display all local variables at the
+    current context.
+
+z. The `@a' variable transformation now prints attributes for unset array
+   variables.
+
+aa. The `@A' variable transformation now prints a declare command that sets a
+    variable's attributes if the variable has attributes but is unset.
+
+bb. `declare' and `local' now have a -I option that inherits attributes and
+    value from a variable with the same name at a previous scope.
+
+cc. When run from a -c command, `jobs' now reports the status of completed jobs.
+
+dd. New `U', `u', and `L' parameter transformations to convert to uppercase,
+    convert first character to uppercase, and convert to lowercase,
+    respectively.
+
+ee. PROMPT_COMMANDS: a new array variable, each element of which can contain a
+    command to be executed like PROMPT_COMMAND.
+
+ff. `ulimit' has a -R option to report and set the RLIMIT_RTTIME resource.
+
+gg. Associative arrays may be assigned using a list of key-value pairs within
+    a compound assignment. Compound assignments where the words are not of
+    the form [key]=value are assumed to be key-value assignments. A missing or
+    empty key is an error; a missing value is treated as NULL. Assignments may
+    not mix the two forms.
+
+hh. New `K' parameter transformation to display associative arrays as key-
+    value pairs.
+
+ii. Writing history to syslog now handles messages longer than the syslog max
+    length by writing multiple messages with a sequence number.
+
+jj. SECONDS and RANDOM may now be assigned using arithmetic expressions, since
+    they are nominally integer variables. LINENO is not an integer variable.
+
+kk. Bash temporarily suppresses the verbose option when running the DEBUG trap
+    while running a command from the `fc' builtin.
+
+ll. `wait -n' now accepts a list of job specifications as arguments and will
+    wait for the first one in the list to change state.
+
+mm. The associative array implementation can now dynamically increase the
+    size of the hash table based on insertion patterns.
+
+nn. HISTFILE is now readonly in a restricted shell.
+
+2. New Features in Readline
+
+a. If a second consecutive completion attempt produces matches where the first
+   did not, treat it as a new completion attempt and insert a match as
+   appropriate.
+
+b. Bracketed paste mode works in more places: incremental search strings, vi
+   overstrike mode, character search, and reading numeric arguments.
+
+c. Readline automatically switches to horizontal scrolling if the terminal has
+   only one line.
+
+d. Unbinding all key sequences bound to a particular readline function now
+   descends into keymaps for multi-key sequences.
+
+e. rl-clear-display: new bindable command that clears the screen and, if
+   possible, the scrollback buffer (bound to emacs mode M-C-l by default).
+
+f. New active mark and face feature: when enabled, it will highlight the text
+   inserted by a bracketed paste (the `active region') and the text found by
+   incremental and non-incremental history searches.
+
+g. Readline sets the mark in several additional commands.
+
+h. Bracketed paste mode is enabled by default (for now).
+
+i. Readline tries to take advantage of the more regular structure of UTF-8
+   characters to identify the beginning and end of characters when moving
+   through the line buffer.
+
+j. The bindable operate-and-get-next command (and its default bindings) are
+   now part of readline instead of a bash-specific addition.
+
+-------------------------------------------------------------------------------
 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.