.\" $MirOS: src/bin/mksh/lksh.1,v 1.23 2017/04/02 13:38:02 tg Exp $

.\"-

.\" Copyright (c) 2008, 2009, 2010, 2012, 2013, 2015, 2016, 2017

.\"	mirabilos <m@mirbsd.org>

.\"

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.\" may a licensor, author or contributor be held liable for indirect,

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.\" of dealing in the work, even if advised of the possibility of such

.\" damage or existence of a defect, except proven that it results out

.\" of said person’s immediate fault when using the work as intended.

.\"-

.\" Try to make GNU groff and AT&T nroff more compatible

.\" * ` generates ‘ in gnroff, so use \`

.\" * ' generates ’ in gnroff, \' generates ´, so use \*(aq

.\" * - generates ‐ in gnroff, \- generates −, so .tr it to -

.\"   thus use - for hyphens and \- for minus signs and option dashes

.\" * ~ is size-reduced and placed atop in groff, so use \*(TI

.\" * ^ is size-reduced and placed atop in groff, so use \*(ha

.\" * \(en does not work in nroff, so use \*(en

.\" * <>| are problematic, so redefine and use \*(Lt\*(Gt\*(Ba

.\" Also make sure to use \& *before* a punctuation char that is to not

.\" be interpreted as punctuation, and especially with two-letter words

.\" but also (after) a period that does not end a sentence (“e.g.\&”).

.\" The section after the "doc" macropackage has been loaded contains

.\" additional code to convene between the UCB mdoc macropackage (and

.\" its variant as BSD mdoc in groff) and the GNU mdoc macropackage.

.\"

.ie \n(.g \{\

.	if ?\*[.T]?ascii? .tr \-\N'45'

.	if ?\*[.T]?latin1? .tr \-\N'45'

.	if ?\*[.T]?utf8? .tr \-\N'45'

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.	ds >= \[>=]

.	ds Rq \[rq]

.	ds Lq \[lq]

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.	if ?\*[.T]?ps? .ds sL `

.	if ?\*[.T]?utf8? .ds sR '

.	if ?\*[.T]?ps? .ds sR '

.	ds aq \(aq

.	ds TI \(ti

.	ds ha \(ha

.	ds en \(en

.\}

.el \{\

.	ds aq '

.	ds TI ~

.	ds ha ^

.	ds en \(em

.\}

.\"

.\" Implement .Dd with the Mdocdate RCS keyword

.\"

.rn Dd xD

.de Dd

.ie ?\\$1?$Mdocdate:? \{\

.	xD \\$2 \\$3, \\$4

.\}

.el .xD \\$1 \\$2 \\$3 \\$4 \\$5 \\$6 \\$7 \\$8

..

.\"

.\" .Dd must come before definition of .Mx, because when called

.\" with -mandoc, it might implement .Mx itself, but we want to

.\" use our own definition. And .Dd must come *first*, always.

.\"

.Dd $Mdocdate: April 2 2017 $

.\"

.\" Check which macro package we use, and do other -mdoc setup.

.\"

.ie \n(.g \{\

.	if ?\*[.T]?utf8? .tr \[la]\*(Lt

.	if ?\*[.T]?utf8? .tr \[ra]\*(Gt

.	ie d volume-ds-1 .ds tT gnu

.	el .ds tT bsd

.\}

.el .ds tT ucb

.\"

.\" Implement .Mx (MirBSD)

.\"

.ie "\*(tT"gnu" \{\

.	eo

.	de Mx

.	nr curr-font \n[.f]

.	nr curr-size \n[.ps]

.	ds str-Mx \f[\n[curr-font]]\s[\n[curr-size]u]

.	ds str-Mx1 \*[Tn-font-size]\%MirOS\*[str-Mx]

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.	nr num-args (\n[arg-limit] - \n[arg-ptr])

.	nr arg-limit \n[arg-ptr]

.	if \n[num-args] \

.	parse-space-vector

.	print-recursive

..

.	ec

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.el \{\

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.		el \{\

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..

.\}

.\"-

.Dt LKSH 1

.Os MirBSD

.Sh NAME

.Nm lksh

.Nd Legacy Korn shell built on mksh

.Sh SYNOPSIS

.Nm

.Bk -words

.Op Fl +abCefhiklmnprUuvXx

.Op Fl +o Ar opt

.Oo

.Fl c Ar string \*(Ba

.Fl s \*(Ba

.Ar file

.Op Ar args ...

.Oc

.Ek

.Sh DESCRIPTION

.Nm

is a command interpreter intended exclusively for running legacy

shell scripts.

It is built on

.Nm mksh ;

refer to its manual page for details on the scripting language.

It is recommended to port scripts to

.Nm mksh

instead of relying on legacy or objectionable POSIX-mandated behaviour,

since the MirBSD Korn Shell scripting language is much more consistent.

.Pp

Do not use

.Nm

as an interactive or login shell; use

.Nm mksh

instead.

.Pp

Note that it's strongly recommended to invoke

.Nm

with

.Fl o Ic posix

to fully enjoy better compatibility to the

.Tn POSIX

standard (which is probably why you use

.Nm

over

.Nm mksh

in the first place);

.Fl o Ic sh

(possibly additionally to the above) may be needed for some legacy scripts.

.Sh LEGACY MODE

.Nm

currently has the following differences from

.Nm mksh :

.Bl -bullet

.It

The

.Ev KSH_VERSION

string identifies

.Nm

as

.Dq Li LEGACY KSH

instead of

.Dq Li 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

.Xr mksh 1

for the versions this document applies to.

.It

.Nm

uses

.Tn POSIX

arithmetic, which has quite a few implications:

The data type for arithmetic operations is the host

.Tn ISO

C

.Vt long

data type.

Signed integer wraparound is Undefined Behaviour; this means that...

.Bd -literal -offset indent

$ echo $((2147483647 + 1))

.Ed

.Pp

\&... 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).

.It

The rotation arithmetic operators are not available.

.It

The shift arithmetic operators take all bits of the second operand into

account; if they exceed permitted precision, the result is unspecified.

.It

Unless

.Ic set -o posix

is active,

.Nm

always uses traditional mode for constructs like:

.Bd -literal -offset indent

$ set -- $(getopt ab:c "$@")

$ echo $?

.Ed

.Pp

POSIX mandates this to show 0, but traditional mode

passes through the errorlevel from the

.Xr getopt 1

command.

.It

Functions defined with the

.Ic function

reserved word share the shell options

.Pq Ic set -o

instead of locally scoping them.

.El

.Sh SEE ALSO

.Xr mksh 1

.Pp

.Pa http://www.mirbsd.org/mksh.htm

.Pp

.Pa http://www.mirbsd.org/ksh\-chan.htm

.Sh CAVEATS

To use

.Nm

as

.Pa /bin/sh ,

compilation to enable

.Ic set -o posix

by default if called as

.Nm sh

.Pq adding Dv \-DMKSH_BINSHPOSIX to Dv CPPFLAGS

is highly recommended for better standards compliance.

.Pp

For better compatibility with legacy scripts, such as many

.Tn Debian

maintainer scripts, Upstart and SYSV init scripts, and other

unfixed scripts, also adding the

.Dv \-DMKSH_BINSHREDUCED

compile-time option to enable

.Em both

.Ic set -o posix -o sh

when the shell is run as

.Nm sh ,

as well as integrating the optional disrecommended

.Xr printf 1

builtin, might be necessary.

.Pp

.Nm

tries to make a cross between a legacy bourne/posix compatibl-ish

shell and a legacy pdksh-alike but

.Dq legacy

is not exactly specified.

.Pp

Talk to the

.Mx

development team using the mailing list at

.Aq miros\-mksh@mirbsd.org

or the

.Li \&#\&!/bin/mksh

.Pq or Li \&#ksh

IRC channel at

.Pa irc.freenode.net

.Pq Port 6697 SSL, 6667 unencrypted

if you need any further quirks or assistance,

and consider migrating your legacy scripts to work with

.Nm mksh

instead of requiring

.Nm .