Announcing: KornShell 93u+m/1.0.4
https://github.com/ksh93/ksh

This is the fourth bugfix release in the ksh 93u+m/1.0 series. Many thanks
to all contributors for their hard work! Compared to an unpatched ksh 93u+
2012-08-01, this release has over a thousand bugs fixed. It incorporates
a fair number of enhancements as well.

### CONTRIBUTORS ###

Work on ksh 93u+m started in May 2020.
Main developers: Martijn Dekker, Johnothan King, hyenias

Direct contributors: Andy Fiddaman, Anuradha Weeraman, atheik, Chase,
Govind Kamat, Harald van Dijk, K. Eugene Carlson, Lev Kujawski, Marc
Wilson, Ryan Schmidt, Sterling Jensen, Trey Valenta, Vincent Mihalkovic

Also includes backported contributions by: David Korn, Glenn Fowler,
Lefteris Koutsofios, Siteshwar Vashisht, Kurtis Rader, Roland Mainz,
Finnbarr P. Murphy, Lijo George, OpenSUSE ksh 93u+ patch authors, Red Hat
ksh 93u+ path authors, Solaris ksh 93u+ patch authors, Debian ksh 93u+
patch authors, Apple ksh 93u+ patch authors, Graphviz maintainers

Many fixes have also been backported from the AT&T 93v- beta as well as
the former ksh2020 project lead by Kurtis Rader and Siteshwar Vashisht;
we appreciate and benefit from their work. Many thanks also to Siteshwar
for graciously donating his 'ksh93' GitHub organisation account!

### HOW TO GET IT ###

Please download the source code tarball from our GitHub releases page:
https://github.com/ksh93/ksh/releases
To build, follow the instructions in README.md or src/cmd/ksh93/README.

Or ask your distribution package manager to upgrade ksh93 to this version.

### HOW TO GET INVOLVED ###

To report a bug, please open an issue at our GitHub page (see above).
Alternatively, email me at martijn@inlv.org with your report.
To get involved in development, read the brief policy information in
README.md and then jump right in with a pull request or email a patch.
See the TODO file in the top-level directory for a to-do list.

### MAIN CHANGES between ksh 93u+m 1.0.3 and 1.0.4 ###

- Fixed multiple scoping-related bugs in the += additive assignment operator.
- A number of crashing bugs have been fixed.
- Various fixes for the Haiku operating system, notably 'ulimit -a' now works.
- Fixed the expansion of out-of-range \n back references in the string part of
  ${parameter//pattern/string}. For example:  v=AB; echo "${v/@(A)B/\0:\1:\2}"
  now yields 'AB:A:' instead of 'AB:A:\2'.
- Fixed quoted '!', '^' and '-' within [bracket] expressions in glob patterns;
  single or double quotes failed to disable their operator behaviour.
- Fixed a bug introduced on 2021-04-04 that incorrectly allowed 'typeset' to
  turn off the readonly and export attributes on a readonly variable.
- In the emacs line editor, the Ctrl+R reverse-search prompt is now visually
  distinct from a literal control character ("^R: " instead of "^R").
- In the vi line editor, fixed the behaviour of 'C', 'c$' and 'I' to be
  consistent with standard vi(1) and with Bolsky & Korn (1995, p. 121).
- Aliases for many GNU long options have been added to the /opt/ast/bin
  built-in commands. Additionally, 'kill -s' now has a --signal long option
  alias compatible with the util-linux option.
- Backported support for 'print -u p' from ksh 93v- for compatibility with
  scripts written for 93v-/ksh2020 (this is equivalent to 'print -p').

### MAIN CHANGES between ksh 93u+m 1.0.2 and 1.0.3 ###

This point release fixes the following:
- An old bug in history expansion (set -H) where any use of the history
  comment character caused processing to be aborted as if it were an invalid
  history expansion.
- A bug in command line options processing that caused short-form
  option equivalents on some built-in commands to be ignored after one use,
  e.g., the new read -a equivalent of read -A.
- Ksh freezing or using excessive memory if HISTSIZE is assigned a
  pathologically large value.
- A bug that caused ksh in the vi editor mode to crash or produce invalid
  completions if ESC = was used at the beginning of a line.

### MAIN CHANGES between ksh 93u+m 1.0.1 and 1.0.2 ###

This bugfix release fixes the interactive shell crashing when one of the
predefined aliases (currently 'history' and 'r') is redefined, whether from
a profile/kshrc script or manually. This crash occurred in two scenarios:
1. when redefining and then unsetting a predefined alias;
2. when redefining a predefined alias and then executing a shell script that
   does not begin with a #! path.

### MAIN CHANGES between ksh 93u+m 1.0.0 and 1.0.1 ###

This is an urgent bugfix release that removes an incorrect exec
optimization that was capable of terminating the execution of scripts
prematurely in certain corner cases. It is known to make the build scripts
of GNU binutils produce corrupted results if ksh is used as /bin/sh.
See https://github.com/ksh93/ksh/issues/507 for more information.

### MAIN CHANGES between ksh 93u+ 2012-08-01 and 93u+m/1.0.0 ###

Roughly a thousand bugs have been fixed, including many serious/critical
bugs. See the NEWS file for more information, and the git commit log for
complete documentation of every fix. Incompatible changes have been
minimised, but not at the expense of fixing bugs. For a list of
potentially incompatible changes, see src/cmd/ksh93/COMPATIBILITY.

Though there was a "no new features, bugfixes only" policy, some new
features were found necessary, either to fix serious design flaws or to
complete functionality that was evidently intended, but not finished.
Below is a summary of these new features.

New command line editor features:

- The forward-delete and End keys are now handled as expected in the
  emacs and vi built-in line editors.

- In the vi and emacs line editors, repeat counts can now also be used for
  arrow keys and the forward-delete key, e.g., <ESC> 7 <left-arrow> works.

- Various keys on extended PC keyboards are now handled as expected in the
  emacs and vi built-in line editors.

New shell language features:

- Pathname expansion (a.k.a. globbing) now never matches the special names
  '.' (current directory) and '..' (parent directory). This change makes a
  pattern like .* useful; it now matches all hidden files (dotfiles) in the
  current directory, without the harmful inclusion of '.' and '..'.

- Tilde expansion can now be extended or modified by defining a .sh.tilde.get
  or .sh.tilde.set discipline function. See the manual for details.

- The &>file redirection shorthand (for >file 2>&1) is now available for all
  scripts and interactive sessions and not only for profile/login scripts.

- Arithmetic expressions in native ksh mode no longer interpret a number
  with a leading zero as octal in any context. Use 8#octalnumber instead
  (e.g. 8#400 == 256). Arithmetic expressions now also behave identically
  within and outside ((...)) and $((...)). If the POSIX mode is turned on,
  a leading zero now denotes an octal number in all arithmetic contexts.

New features in built-in commands:

- Usage error messages now show the --help/--man self-documentation options.

- Path-bound built-ins (such as /opt/ast/bin/cat) can now be executed by
  invoking the canonical path, so the following will now work as expected:
	$ /opt/ast/bin/cat --version
	  version         cat (AT&T Research) 2012-05-31

- 'cd' now supports an -e option that, when combined with -P, verifies
  that $PWD is correct after changing directories; this helps detect
  access permission problems. See:
  https://www.austingroupbugs.net/view.php?id=253

- 'command -x' now looks for external commands only, skipping built-ins.
  In addition, its xargs-like functionality no longer freezes the shell on
  Linux and macOS, making it effectively a new feature on these systems.

- 'printf' now supports a -v option as in bash. This assigns formatted
  output directly to variables, which is very fast and will not strip
  final newline (\n) characters.

- 'redirect' now checks if all arguments are valid redirections before
  performing them. If an error occurs, it issues an error message instead
  of terminating the shell.

- 'return', when used to return from a function, can now return any
  status value in the 32-bit signed integer range, like on zsh. However,
  due to a traditional Unix kernel limitation, $? is still trimmed to its
  least significant 8 bits whenever a shell or subshell exits.

- 'suspend' now refuses to suspend a login shell, as there is probably no
  parent shell to return to and the login session would freeze.

- 'test'/'[' now supports all the same operators as [[ (including =~,
  \<, \>) except for the different 'and'/'or' operators. Note that
  'test'/'[' remains deprecated due to its unfixable pitfalls;
  [[ ... ]] is recommended instead.

- 'times' now gives high precision output in a POSIX compliant format.

- 'type'/'whence': Two bash-like flags were backported from ksh 93v-:
  - 'whence -P/type -P' is an alias to the existing -p flag.
  - 'whence -t/type -t' will print only the type of a command in a
    simple format that is designed to be easy to use for scripts.

- 'typeset' has a new '-g' flag that forces variables to be created or
  modified at the global scope regardless of context, as on bash 4.2+.

- 'typeset' now gives an informative error message if an incompatible
  combination of options is given.

- 'ulimit': Added three options inspired by bash:
  - 'ulimit -k' sets the maximum number of kqueues.
  - 'ulimit -P' sets the maximum number of pseudo-terminals.
  - 'ulimit -R' sets the maximum time in microseconds a real-time process
    can run before blocking.
  Note that not all operating systems support the limits set by these options.

- 'whence -v/-a' now reports the location of autoloadable functions.

New features in shell options:

- When the -b/--notify shell option is on and the vi or emacs/gmacs shell
  line editor is in use, 'Done' and similar notifications from completed
  background jobs are now inserted directly above the line you're typing,
  without affecting your command line display.

- A new --functrace long-form shell option causes the -x/--xtrace option's
  state and the DEBUG trap action to be inherited by function scopes instead
  of being reset to default. Changes made to them within a function scope
  still do not propagate back to the parent scope. Similarly, this option
  also causes the DEBUG trap action to be inherited by subshells.

- A new --globcasedetect shell option is added on operating systems where
  we can check for a case-insensitive file system (currently Linux, macOS,
  QNX 7.0+, and Windows/Cygwin). When this option is turned on, pathname
  expansion (globbing), as well as tab completion on interactive shells,
  automatically become case-insensitive depending on the file system.
  This is separately determined for each pathname component.

- Enhancement to -G/--globstar: symbolic links to directories are now
  followed if they match a normal (non-**) glob pattern. For example, if
  '/lnk' is a symlink to a directory, '/lnk/**' and '/l?k/**' now work as
  you would expect.

- The new --histreedit and --histverify options modify history expansion
  (--histexpand). If --histreedit is on and a history expansion fails, the
  command line is reloaded into the next prompt's edit buffer, allowing
  corrections. If --histverify is on, the results of a history expansion are
  not immediately executed but instead loaded into the next prompt's edit
  buffer, allowing further changes.

- A new --nobackslashctrl shell option disables the special escaping
  behaviour of the backslash character in the emacs and vi built-in editors.
  Particularly in the emacs editor, this makes it much easier to go back,
  insert a forgotten backslash into a command, and then continue editing
  without having your next arrow key replace your backslash with garbage.

- A new --posix shell option has been added to ksh 93u+m that makes the
  ksh language more compatible with other shells by following the POSIX
  standard more closely. See the manual page for details. It is enabled by
  default if ksh is invoked as sh, otherwise it is disabled by default.
