1LKSH(1) BSD General Commands Manual LKSH(1)
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4 lksh — Legacy Korn shell built on mksh
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7 lksh [-+abCefhiklmnprUuvXx] [-+o opt] [-c string | -s | file [args ...]]
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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 objectionable POSIX-mandated behaviour,
14 since the MirBSD Korn Shell scripting language is much more consistent.
15 Do not use lksh as an interactive or login shell; use mksh instead.
17 Note that it's strongly recommended to invoke lksh with -o posix to fully
19 enjoy better compatibility to the POSIX standard (which is probably why
20 you use lksh over mksh in the first place); -o sh (possibly additionally
21 to the above) may be needed for some legacy scripts.
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24 lksh currently has the following differences from mksh:
25 · The KSH_VERSION string identifies lksh as “LEGACY KSH” instead of
27 “MIRBSD KSH”. Note that the rest of the version string is identical
28 between the two shell flavours, and the behaviour and differences can
29 change between versions; see the accompanying manual page mksh(1) for
30 the versions this document applies to.
31 · lksh uses POSIX arithmetic, which has quite a few implications: The
33 data type for arithmetic operations is the host ISO C long data type.
34 Signed integer wraparound is Undefined Behaviour; this means that...
35 $ echo $((2147483647 + 1))
37 ... is permitted to, e.g. delete all files on your system (the figure
39 differs for non-32-bit systems, the rule doesn't). The sign of the
40 result of a modulo operation with at least one negative operand is
41 unspecified. Shift operations on negative numbers are unspecified.
42 Division of the largest negative number by -1 is Undefined Behaviour.
43 The compiler is permitted to delete all data and crash the system if
44 Undefined Behaviour occurs (see above for an example).
45 · The rotation arithmetic operators are not available.
47 · The shift arithmetic operators take all bits of the second operand
49 into account; if they exceed permitted precision, the result is
50 unspecified.
51 · Unless set -o posix is active, lksh always uses traditional mode for
53 constructs like:
54 $ set -- $(getopt ab:c "$@")
56 $ echo $?
57 POSIX mandates this to show 0, but traditional mode passes through
59 the errorlevel from the getopt(1) command.
60 · Functions defined with the function reserved word share the shell
62 options (set -o) instead of locally scoping them.
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65 mksh(1)
66 http://www.mirbsd.org/mksh.htm
68 http://www.mirbsd.org/ksh-chan.htm
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72 To use lksh as /bin/sh, compilation to enable set -o posix by default if
73 called as sh (adding -DMKSH_BINSHPOSIX to CPPFLAGS) is highly recommended
74 for better standards compliance.
75 For better compatibility with legacy scripts, such as many Debian main‐
77 tainer scripts, Upstart and SYSV init scripts, and other unfixed scripts,
78 also adding the -DMKSH_BINSHREDUCED compile-time option to enable both
79 set -o posix -o sh when the shell is run as sh, as well as integrating
80 the optional disrecommended printf(1) builtin, might be necessary.
81 lksh tries to make a cross between a legacy bourne/posix compatibl-ish
83 shell and a legacy pdksh-alike but “legacy” is not exactly specified.
84 Talk to the MirBSD development team and users using the mailing list at
86 <miros-mksh@mirbsd.org> (please note the EU-DSGVO/GDPR notice on
87 http://www.mirbsd.org/rss.htm#lists and in the SMTP banner!) or the
88 #!/bin/mksh (or #ksh) IRC channel at irc.freenode.net (Port 6697 SSL,
89 6667 unencrypted) if you need any further quirks or assistance, and con‐
90 sider migrating your legacy scripts to work with mksh instead of requir‐
91 ing lksh.
92MirBSD September 4, 2020 MirBSD