Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!usenet.ins.cwru.edu!cwns1!chet
From: chet@cwns1.CWRU.EDU (Chet Ramey)
Newsgroups: comp.unix.shell
Subject: Re: bourne shell query
Message-ID: <1990Sep6.141133.3391@usenet.ins.cwru.edu>
Date: 6 Sep 90 14:11:33 GMT
References: <75@iconsys> <925@hls0.hls.oz> <SCOTT.90Sep5124415@tab29.larc.nasa.gov>
Sender: news@usenet.ins.cwru.edu
Reply-To: chet@po.CWRU.Edu
Organization: Case Western Reserve Univ. Cleveland, Ohio, (USA)
Lines: 77

In article <SCOTT.90Sep5124415@tab29.larc.nasa.gov> scott@tab29.larc.nasa.gov (Scott Yelich) writes:

>1) if [ "$1" = "$2" ]; then
>     echo "Yeas!"
>   else
>     echo "No-way!"
>   fi

What if $1 = '=' or '-t'?

>2) test "$1" = "$2" && echo "Yeas!" || echo "No-way!"

cwns1$ foo()
> {
> /bin/test "$1" = "$2" && echo "Yeas" || echo "No-way"
> }
cwns1$ foo -r -r
test: too many arguments
No-way

>What about?
>
>3) if [ "$1" ]; then
>     echo "Yup!"
>   fi

What if $1 = `-f' or `-r'?

cwns1$ foo()
> {
> if [ "$1" ] ; then
> echo yup
> fi
> }
cwns1$ foo a
yup
cwns1$ foo -r
[: argument expected

>4) eval ${1:+'echo "Yup!"'}

This *is* a nice way to test whether or not a variable is set.

Nobody seems to consider the case statement, which avoids these problems:

equal()
{
	case "$1" in
		"$2")	return 0
			;;
		*)	return 1
			;;
	esac
}

cwns1$ equal a b
cwns1$ echo $?
1
cwns1$ equal a a
cwns1$ echo $?
0
cwns1$ equal -r -r
cwns1$ echo $?
0

>Now, does anyone have and BOURNE SHELL (ie: /bin/sh) routines to do math?

Well, the shell running as /bin/sh on my machine is bash, and it has
$[] to do arithmetic substitution.

Chet
-- 
Chet Ramey				``Levi Stubbs' tears run down
Network Services Group			  his face...''
Case Western Reserve University	
chet@ins.CWRU.Edu