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.

       Note that it's strongly recommended to invoke lksh with at least the -o posix option, if  not  both  that
       and  -o sh, to fully enjoy better compatibility to the POSIX standard (which is probably why you use lksh
       over mksh in the first place) or legacy scripts, respectively.

LEGACY MODE

       lksh currently 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”.  Note that the rest
           of the version string is identical between the two shell flavours, and the behaviour and  differences
           can  change between versions; see the accompanying manual page mksh(1) for the versions this document
           applies to.

       •   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; this means that...

                 $ echo $((2147483647 + 1))

           ... is permitted to, e.g. delete all files on your system (the figure differs for non-32-bit systems,
           the rule doesn't).  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 (see above for an example).

       •   lksh only offers the traditional ten file descriptors to scripts.

       •   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.

       •   Unlike AT&T UNIX ksh, mksh in -o posix or -o sh mode and lksh  do  not  keep  file  descriptors  >  2
           private from sub-processes.

       •   Functions defined with the function reserved word share the shell options (set -o) instead of locally
           scoping them.

SEE ALSO

       mksh(1)

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

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

CAVEATS

       The distinction between the shell variants (lksh / mksh) and shell flags (-o posix / sh) will be reworked
       for an upcoming release.

       To  use  lksh  as  /bin/sh,  compilation  to  enable  set  -o  posix by default if called as sh is highly
       recommended for better standards compliance.  For better compatibility with legacy scripts, such as  many
       Debian  maintainer  scripts, Upstart and SYSV init scripts, and other unfixed scripts, using the compile-
       time options for enabling both set -o posix -o sh when the shell is run as sh is recommended.

       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 currently 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                                          February 11, 2016                                        LKSH(1)