LKSH(1) BSD Reference Manual LKSH(1)
lksh - Legacy Korn shell built on mksh
lksh [-+abCefhiklmnprUuvXx] [-+o opt] [-c string | -s | file [args ...]]
lksh is a command interpreter intended exclusively for running legacy shell scripts. It is built on mksh; refer to its manual page for details on the scripting language. It is recommended to port scripts to mksh in- stead of relying on legacy or idiotic POSIX-mandated behaviour, since the MirBSD Korn Shell scripting language is much more consistent.
lksh has the following differences from mksh: • There is no explicit support for interactive use, nor any command line editing or history code. Hence, lksh is not suitable as a user's login shell, either; use mksh instead. • The KSH_VERSION string identifies lksh as "LEGACY KSH" instead of "MIRBSD KSH". • lksh only offers the traditional ten file descriptors to scripts. • lksh uses POSIX arithmetics, which has quite a few implications: The data type for arithmetics is the host ISO C long data type. Signed integer wraparound is Undefined Behaviour. The sign of the result of a modulo operation with at least one negative operand is unspecified. Shift operations on negative numbers are unspecified. Division of the largest negative number by -1 is Undefined Behaviour. The compiler is permitted to delete all data and crash the system if Undefined Behaviour occurs. • The rotation arithmetic operators are not available. • The shift arithmetic operators take all bits of the second operand into account; if they exceed permitted precision, the result is un- specified. • The GNU bash extension &> to redirect stdout and stderr in one go is not parsed. • The mksh command line option -T is not available. • Unless set -o posix is active, lksh always uses traditional mode for constructs like: $ set -- $(getopt ab:c "$@") $ echo $? POSIX mandates this to show 0, but traditional mode passes through the errorlevel from the getopt(1) command. • lksh, unlike AT&T UNIX ksh, does not keep file descriptors > 2 private.
mksh(1) https://www.mirbsd.org/mksh.htm https://www.mirbsd.org/ksh-chan.htm
To use lksh as /bin/sh, compilation to enable set -o posix by default is highly recommended for better standards compliance. lksh tries to make a cross between a legacy bourne/posix compatibl-ish shell and a legacy pdksh-alike but "legacy" is not exactly specified. The set built-in command does not have all options one would expect from a full-blown mksh or pdksh. Talk to the MirOS development team using the mailing list at <email@example.com> or the #!/bin/mksh (or #ksh) IRC channel at irc.freenode.net (Port 6697 SSL, 6667 unencrypted) if you need any furth- er quirks or assistance, and consider migrating your legacy scripts to work with mksh instead of requiring lksh. MirOS May 22, 2013 1
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