ksh 93u+m 1.0.0-beta.2

In May 2020, when every KornShell (ksh93) development project was abandoned, development was rebooted in a new fork based on the last stable AT&T version: ksh 93u+. This new fork is called ksh 93u+m as a permanent nod to its origin. We're restarting it at version 1.0. Seven months after the first beta, the second one is ready. Please test this second beta and report any bugs you find, or help us fix known bugs.

We're now the default ksh93 in some OS distributions, at least Debian and Slackware! Even though we don't think it's stable release quality yet, the consensus seems to be that 93u+m is already much better than the last AT&T release.

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MAIN CHANGES between 1.0.0-beta.1 and 1.0.0-beta.2

New features in built-in commands:

• 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

• 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.

• The return command, 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 leaving a (sub)shell environment.

• 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.

Shell language changes:

• Several improvements were made to the --noexec shell code linter.

• 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 $((...)).

• POSIX compatibility mode fixes (only applicable with the --posix shell option on): - A leading zero is now consistently recognised as introducing an octal number in all arithmetic contexts. - $((inf)) and $((nan)) are now interpreted as regular variables. - The . built-in no longer runs ksh functions and now only runs files.

Bugs fixed:

• . and .. are now once again completed by tab completion.

• If SIGINT is set to ignore, the interactive shell no longer exits on Ctrl+C.

• ksh now builds and runs on Apple's new M1 hardware.

• The return and exit commands no longer risk triggering actual signals by returning or exiting with a status > 256.

• Ksh no longer behaves badly when parsing a type definition command (typeset -T or enum) without executing it or when executing it in a subshell. Types can now safely be defined in subshells and defined conditionally as in if condition; then enum ...; fi.

• Discipline functions, especially those applied to PS2 or .sh.tilde, will no longer crash your shell upon being interrupted or throwing an error.

• Fixed a bug that could corrupt output if standard output is closed upon initialising the shell.

• Fixed a bug in the [[ ... ]] compound command: the ! logical negation operator now correctly negates another !, e.g., [[ ! ! 1 -eq 1 ]] now returns 0/true. Note that this has always been the case for test/[.

• Fixed SHLVL so that replacing ksh by itself (exec ksh) will not increase it.

• Arithmetic expressions are no longer allowed to assign out-of-range values to variables of types declared with enum.

• The time keyword no longer makes the --errexit shell option ineffective.

• Various bugs in libcmd built-in commands (those bound to the /opt/ast/bin path by default) have been fixed.

• Various other crashing bugs have been fixed.

Fixes for the shcomp byte code compiler:

• shcomp is now able to compile scripts that define types using enum.

• shcomp now refuses to mess up your terminal by writing bytecode to it.

MAIN CHANGES between ksh 93u+ 2012-08-01 and 93u+m 1.0.0-beta.1

Hundreds of bugs have been fixed, including many serious/critical bugs. This includes upstreamed patches from OpenSUSE, Red Hat, and Solaris, fixes backported from the abandoned 93v- beta and ksh2020 fork, as well as many new fixes from the community. 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 count parameters can now also be used for the arrow keys and the forward-delete key. E.g., in emacs mode, 7 will now move the cursor seven positions to the left. In vi control mode, this would be entered as: 7 .

New shell language features:

• The &>file redirection shorthand (for >file 2>&1) is now available for all scripts and interactive sessions and not only for profile/login scripts, bringing ksh 93u+m in line with mksh, bash, and zsh.

• File name generation (a.k.a. pathname expansion, a.k.a. globbing) now never matches the special navigational 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. This replaces a 2004 undocumented attempt to add this functionality via a .sh.tilde command, which never worked and crashed the shell. See the manual for details on the new method.

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

• 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.

• 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.

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

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

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

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

New features in shell options:

• A new --globcasedetect shell option is added on OSs where we can check for a case-insensitive file system (currently Windows/Cygwin, macOS, Linux and QNX 7.0+). When this option is turned on, file name generation (globbing), as well as file name tab completion on interactive shells, automatically become case-insensitive on file systems where the difference between upper and lower case is ignored for file names. This is transparently determined for each directory, so a path pattern that spans multiple file systems can be part case-sensitive and part case-insensitive.

• 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 backward, insert a forgotten backslash into a command, and then continue editing without having your next cursor key replace your backslash with garbage. Note that Ctrl+V (or whatever other character was set using stty lnext) always escapes all control characters in either editing mode.

• 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.

• 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.