From: brian hiles <b...@rainey.blueneptune.com>
Subject: Re: How to distinguish between ksh88 & ksh93
Date: 1999/11/15
Message-ID: <s30uv6sehsq6@corp.supernews.com>
X-Deja-AN: 548999926
References: <38300E2A.E84A3D0A@siep.shell.com> <80pari$ntt$1@magnum.mmm.com>
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Dan Mercer <damer...@mmm.com> wrote:
> In article <38300E2A.E84A3...@siep.shell.com>,
> PH <p.p.h.vanha...@siep.shell.com> writes:
> check_version() { typeset version=ksh93; }
> version=ksh88
> check_version

To determine the version of a shell throughto existance of
non-existance of a bug is not the most robust way to do this.

I give you my script "whichshell" which you may use in your .profile
or strip out the pertainent criterion code, if you like.  It has
the property of recognizing (and being run within) the csh shells.

# whichshell 2>&- || SHTYPE=SH_1977 : do NOT eliminate this first comment line!
#*TAG:48056 5:Nov 21 1998:0755:whichshell:
# Author: Brian Hiles <b...@iname.com>
# Copyright: (c) 1997-1998
# Description: determine which shell this script runs under
# Inspired-by: hei...@darwin.noris.de (Heiner Steven)
# Name: whichshell
# Sccs: @(#)whichshell.sh 1.2 1998/05 b...@iname.com (Brian Hiles)
# Usage: whichshell [script [script-parameter]...]
# Version: 1.02

#XXX consider allowing "init.KSH" instead of "init.KSH_19??"
#XXX SH_OLD -> SH_1977, etc.
#XXX SH_POSIX -> SH_199?
#XXX thoroughly document differences between early bourne shells in _man-page_

#01 COMMON CORE CODE
unset a || SHTYPE=SH_OLD		# ignore potential error message
set a = "$*"
test "$a" = "$*" && goto CSH

#02 BOURNE FAMILY
PATH= export PATH
case $3 in
'')	shcmd='echo ' ;;
*)	set -- $3
	shcmd=". ${1?}."		# bash bug: "var=value shift" not poss!
	shift ;;
esac
# From: werner.bu...@ubs.com (Werner Burri)
# zsh 2.5.x/3.0.x error: "whichshell: read-only variable: LINENO [60]"
IFS=' ' LINENO= RANDOM= a=$[1] retval=0
a=2 a=$[3] wait 2>/dev/null
case $a:$LINENO:$RANDOM in
1*)	# use BASH_VERSION?
	if (: ${!a}) 2>/dev/null
	then	SHTYPE=BASH_2		# bash 2.00 (IRIX 5.x)
	else	SHTYPE=BASH_1		# bash 1.14.7(2) (IRIX 5.x)
		# From: werner.bu...@ubs.com (Werner Burri)
		[ "${ZSH_VERSION:-${VERSION#zsh }}" > 2.5 ] &&
		SHTYPE=ZSH_${ZSH_VERSION:-${VERSION#zsh }}
	fi ;;
'$[3]::'*)
	SHTYPE=KSH_1986 ;;		# ksh 6/3/86
$\[[13]]:1:[0-9]*)
	# some ksh88s are modified to apparently conform to POSIX 1003.2
	if (: ${.sh.version}) 2>/dev/null
	then	SHTYPE=KSH_1993		# ksh M-12/28/93e (SunOS 4.x, IRIX 5.x)
	else	SHTYPE=KSH_1988		# ksh 11/16/88f (AIX 4.x, OSF/1 3.x)
		#SHTYPE=KSH_1988POSIX	# ksh 11/16/88f (AIX 4.x, OSF/1 3.x)
	fi ;;
'$[3]::')
	SHTYPE=SH_1994 ;;		# sh SVR4 (UnixWare)
2::)	case $SHTYPE in
	SH_OLD)	;;
	*)	if (_(){ :;}) 2>/dev/null
		then	SHTYPE=SH_1983	# sh SVR3 Unix 
		else	SHTYPE=SH_1977	# sh SVR2 Unix
		fi ;;
	esac ;;
#3*)	SHTYPE=ZSH_ ;;			# zsh 2.3.1 (IRIX 5.x)
*)	retval=1 SHTYPE=`
		IFS=/
		set -- ${SHELL:-UNKNOWN}
		until test \$# -eq 1
		do	shift
		done
		echo "\$1"
	` ;;
esac
eval $shcmd$SHTYPE
exit $retval

#03 CSHELL FAMILY
CSH:
unset path
if ("X$a" == X) then
	set shcmd = 'echo '
else
	set argv = ($a) shcmd = "source $1."
	shift
endif
set a = /b/c.d.e retval = 0
switch ($a:t:r:e)
case c.d.e:r:e:				# csh (SunOS 4.x)
case c:d:e:r:e:				# csh (IRIX 5.x)
	set SHTYPE = CSH
	breaksw
case d:					# tcsh 1.2 1993/07/15 (IRIX 5.x)
	set SHTYPE = TCSH
	breaksw
default:
	if ! ($?shell) set shell = UNKNOWN retval = 1
	if ("X$shell" == X) set shell = UNKNOWN retval = 1
	set SHTYPE = $shell:t
	breaksw
endsw
eval $shcmd$SHTYPE
exit $retval
-- 

#04 EMBEDDED MANPAGE FOR "src2man"
#++
NAME
	whichshell - determine which shell this script runs under

SYNOPSIS
	whichshell [script [script-parameter(s)]]

DESCRIPTION
	With no arguments, the determined value of <shell> is printed
	to stdout. If this cannot be determined, $SHELL is assumed if
	set and non-null, otherwise string "UNKNOWN".

	With <script> argument and optional <parameter(s)>, the script
	<script>.<shell> is sourced with its positional parameters set
	to <parameter(s)>.

	Whichshell knows about bash 1.x/2.x, csh, ksh86/88/93, V7/SVR2 sh,
	SVR3 sh, POSIX sh, tcsh, #XXXand zsh.

EXAMPLE
	csh -f whichshell init p1 p2 p3
	sh -f whichshell init p1 p2 p3
	ksh -f whichshell init p1 p2 p3

	It is assumed that files "init.{CSH,KSH_1988,SH}" exist having
	valid csh, ksh[88], and sh code, respectively. Or another
	technique may be to create links "init.KSH_1988" and "init.KSH_1993"
	that point to "init.SH", and a link "init.TCSH" to "init.CSH".

RETURN VALUE
	For the case of no arguments:
		0 if the shell is able to be determined, else 1.
	else,
		if the sourced file does not exist: 1, else the same
		as above (barring an explicit "exit" command therein.)

CAVEATS
	This script cannot be sourced; it must be executed within a
	subshell.

	Bash 1.x will attempt to source an $ENV script meant for ksh or
	other shells.

	Different sources document the release year of the various shells
	distributed with the canonical releases of Unix; however, whichshell
	only stipulates that such numbers be formally increasing for each
	major family of shell.

	To be truly robust for very ancient sh's: eliminate all comments
	but the first.

	Until weirdnik zsh can decide on how to act whether interactive
	or not, whichshell cannot be expected to either.

BUGS
	Positional parameter(s) cannot have embedded whitespace or
	special characters.

#--

-Brian