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 recommended to port  scripts
       to  mksh  instead  of  relying on legacy or idiotic POSIX-mandated behaviour, 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  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 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 MirOS0 development team using the mailing list at <miros-mksh@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                                           LKSH(1)