1LKSH(1)                   BSD General Commands Manual                  LKSH(1)
2

NAME

4     lksh — Legacy Korn shell built on mksh
5

SYNOPSIS

7     lksh [-+abCefhiklmnprUuvXx] [-+o opt] [-c string | -s | file [args ...]]
8

DESCRIPTION

10     lksh is a command interpreter intended exclusively for running legacy
11     shell scripts.  It is built on mksh; refer to its manual page for details
12     on the scripting language.  It is recommended to port scripts to mksh
13     instead of relying on legacy or idiotic POSIX-mandated behaviour, since
14     the MirBSD Korn Shell scripting language is much more consistent.
15

LEGACY MODE

17     lksh has the following differences from mksh:
18
19     ·   lksh is not suitable for use as /bin/sh.
20
21     ·   There is no explicit support for interactive use, nor any command
22         line editing or history code.  Hence, lksh is not suitable as a
23         user's login shell, either; use mksh instead.
24
25     ·   The KSH_VERSION string identifies lksh as “LEGACY KSH” instead of
26         “MIRBSD KSH”.
27
28     ·   lksh only offers the traditional ten file descriptors to scripts.
29
30     ·   lksh uses POSIX arithmetics, which has quite a few implications: The
31         data type for arithmetics is the host ISO C long data type.  Signed
32         integer wraparound is Undefined Behaviour.  The sign of the result of
33         a modulo operation with at least one negative operand is unspecified.
34         Shift operations on negative numbers are unspecified.  Division of
35         the largest negative number by -1 is Undefined Behaviour.  The com‐
36         piler is permitted to delete all data and crash the system if Unde‐
37         fined Behaviour occurs.
38
39     ·   The rotation arithmetic operators are not available.
40
41     ·   The shift arithmetic operators take all bits of the second operand
42         into account; if they exceed permitted precision, the result is
43         unspecified.
44
45     ·   The GNU bash extension &> to redirect stdout and stderr in one go is
46         not parsed.
47
48     ·   The mksh command line option -T is not available.
49
50     ·   Unless set -o posix is active, lksh always uses traditional mode for
51         constructs like:
52
53               $ set -- $(getopt ab:c "$@")
54               $ echo $?
55
56         POSIX mandates this to show 0, but traditional mode passes through
57         the errorlevel from the getopt(1) command.
58
59     ·   lksh, unlike AT&T UNIX ksh, does not keep file descriptors > 2 pri‐
60         vate.
61

SEE ALSO

63     mksh(1)
64
65     https://www.mirbsd.org/mksh.htm
66
67     https://www.mirbsd.org/ksh-chan.htm
68

CAVEATS

70     lksh tries to make a cross between a legacy bourne/posix compatibl-ish
71     shell and a legacy pdksh-alike but “legacy” is not exactly specified.
72
73     The set built-in command does not have all options one would expect from
74     a full-blown mksh or pdksh.
75
76     Talk to the MirOS development team using the mailing list at
77     <miros-mksh@mirbsd.org> or the #!/bin/mksh (or #ksh) IRC channel at
78     irc.freenode.net (Port 6697 SSL, 6667 unencrypted) if you need any fur‐
79     ther quirks or assistance, and consider migrating your legacy scripts to
80     work with mksh instead of requiring lksh.
81
82MirBSD                            May 2, 2013                           MirBSD
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