This is a terse description of the new features added to bash-5.3 since
the release of bash-5.2.  As always, the manual page (doc/bash.1) is
the place to look for complete descriptions.

1. New Features in Bash

a. When checking whether a script file argument is a binary file, check the
   first two lines of a script if the first line begins with `#!'.

b. Bash does a better job of preserving user-supplied quotes around a word
   completion, instead of requoting it.

c. Bash reports the starting line number in an error message about an
   unterminated compound command like `if' without a `fi'.

d. Implement the POSIX requirement that running the `jobs' builtin removes
   jobs from the jobs list.

f. Call bash signal handlers while executing programmable completion commands,
   instead of readline's.

g. Print an error message if a regular expression used with [[ fails to compile.

h. The `umask' builtin now has additional features for full POSIX conformance.

i. `type -a -P' reports both hashed pathnames and the result of a $PATH search.

j. `trap' has a new -P option that prints the trap action associated with each
   signal argument.

k. The `command' builtin preceding a declaration builtin (e.g., `declare')
   preserves the special asisgnment statement parsing for the declation
   builtin. This is a new POSIX requirement.

l. `printf' uses the `alternate form' for %q and %Q to force single quoting.

m. `printf' now interprets %ls (%S) and %lc (%C)nas referring to wide strings
   and characters, respectively, when in a multibyte locale.

n. The shell can be compiled with a different default value for the
   patsub_replacement option.

o. Check for window size changes during trap commands, `bind -x' commands,
   and programmable completion.

p. Treat a NULL value for $PATH as equivalent to ".".

p. New loadable builtins: kv, strptime

q. GLOBSORT: new variable to specify how to sort the results of pathname
   expansion (name, size, blocks, mtime, atime, ctime, none) in ascending
   or descending order.

r. `compgen' has a new option: -V varname. If supplied, it stores the generated
   completions into VARNAME instead of printing them on stdout.

s. New form of command substitution: ${ command; } or ${|command;} to capture
   the output of COMMAND without forking a child process and using pipes.

t. array_expand_once: new shopt option, replaces assoc_expand_once

u. complete/compopt new option: fullquote; sets rl_full_quoting_desired so all
   possible completions are quoted as if they were filenames.

v. Command timing now allows precisions up to 6 digits instead of 3 in
   $TIMEFORMAT.

w. BASH_MONOSECONDS: new dynamic variable that returns the value of the
   system's monotonic clock, if one is available.

x. BASH_TRAPSIG: new variable, set to the numeric signal number of the trap
   being executed while it's running.

y. The checkwinsize option can be used in subshell commands started from
   interactive shells.

z. In posix mode, the test command < and > binary primaries compare strings
   using the current locale.

aa. bind -x allows new key binding syntax: separate the key sequence and the
    command string with whitespace, but require the command string to be
    double-quoted if this is used. This allows different quoting options for
    the command string.

bb. Print commands bound to key sequences using `bind -x' with the new key
    binding syntax it allows.

cc. `read' has a new `-E' option to use readline but with the default bash
    completion (including programmable completion).

dd. New bindable readline command name: `bash-vi-complete'.

ee. New test builtin behavior when parsing a parenthesized subexpression and
    test was given more than 4 arguments: scan forward for a closing paren and
    call posixtest() if there are 4 or fewer arguments between the parentheses.
    Added for compatibility with coreutils test, dependent on the shell
    compatibility level. Such expressions remain ambiguous.

2. New Features in Readline

a. Output a newline if there is no prompt and readline reads an empty line.

b. The history library falls back to stdio when writing the history list if
   mmap fails.

c. New bindable variable `search-ignore-case', causes readline to perform
   case-insensitive incremental and non-incremental history searches.

d. rl_full_quoting_desired: new application-settable variable, causes all
   completions to be quoted as if they were filenames.

e. rl_macro_display_hook: new application-settable function pointer, used if
   the application wants to print macro values itself instead of letting
   readline do it

f. rl_reparse_colors: new application-callable function, reparses $LS_COLORS
   (presumably after the user changes it)

g. rl_completion_rewrite_hook: new application-settable function pointer,
   called to modify the word being completed before comparing it against
   pathnames from the file system.

h. execute-named-command: a new bindable command that reads the name of a
   readline command from the standard input and executes it. Bound to M-x
   in emacs mode by default.

i. Incremental and non-incremental searches now allow ^V/^Q (or, in the former
   case, anything bound to quoted-insert) to quote characters in the search
   string.