LKSH(1)                            BSD General Commands Manual                            LKSH(1)

NAME
     lksh — Legacy Korn shell built on mksh

SYNOPSIS
     lksh [-+abCefhiklmnprUuvXx] [-+o opt] [-c string | -s | file [args ...]]

DESCRIPTION
     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 recom‐
     mended to port scripts to mksh instead of relying on legacy or idiotic POSIX-mandated behav‐
     iour, since the MirBSD Korn Shell scripting language is much more consistent.

LEGACY MODE
     lksh has the following differences from mksh:

     ·   There is no explicit support for interactive use, nor any command line editing or his‐
         tory 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 op‐
         erand 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 unspecified.

     ·   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.

SEE ALSO
     mksh(1)

     https://www.mirbsd.org/mksh.htm

     https://www.mirbsd.org/ksh-chan.htm

CAVEATS
     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 <miros-mksh AT mirbsd.org> or the
     #!/bin/mksh (or #ksh) IRC channel at irc.freenode.net (Port 6697 SSL, 6667 unencrypted) if
     you need any further quirks or assistance, and consider migrating your legacy scripts to
     work with mksh instead of requiring lksh.

MirBSD                                     May 22, 2013                                    MirBSD