|LKSH(1)||General Commands Manual||LKSH(1)|
lksh — Legacy Korn
shell built on mksh
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 objectionable
POSIX-mandated behaviour, since the MirBSD Korn Shell scripting language is
much more consistent.
Do not use
lksh as an interactive or login
Note that it's strongly recommended to invoke
posix to fully enjoy better compatibility to the
POSIX standard (which is probably why you use
mksh in the first place);
sh (possibly additionally
to the above) may be needed for some legacy scripts.
lksh currently has the following
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.
lkshuses POSIX arithmetic, which has quite a few implications: The data type for arithmetic operations 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).
- 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.
set -o posixis active,
lkshalways 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.
- Functions defined with the
functionreserved word share the shell options (
set -o) instead of locally scoping them.
/bin/sh, compilation to enable
-o posix by default if called as
CPPFLAGS) is highly recommended for better standards
For better compatibility with legacy scripts, such as
many Debian maintainer scripts, Upstart and SYSV init scripts, and other
unfixed scripts, also adding the
compile-time option to enable
set -o posix -o sh when the shell is run as
sh, as well as integrating the optional
disrecommended printf(1) builtin, might be necessary.
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.
Talk to the MirBSD development team and users using the mailing
or in the
#!/bin/mksh IRC channel; mind the infos
from http://www.mirbsd.org/mksh-faq.htm#contact for
either. Consider migrating your legacy scripts to work with
mksh instead of requiring
|June 15, 2021||MirBSD|