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Date: Tue, 16 Feb 1999 00:04:26 -0500
To: Christopher Faylor <cgf AT cygnus DOT com>, <cygwin AT sourceware DOT cygnus DOT com>
From: "Pierre A. Humblet" <Pierre DOT Humblet AT eurecom DOT fr>
Subject: Re: sources
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At 11:14 PM 2/15/99 -0500, Christopher Faylor wrote:
>If someone can point me to some documentation that proves that ash is not
>working like a standard UNIX /bin/sh, then I'll be happy to change my mind.

That's a good point. Where can we find documentation about ash? 
From experimenting with it, it looks like ash can do more than (some) sh. For example the %% construct can be used to test if an argument is a switch. However this feature doesn't work reliably:

~: sh try_ash yyy
Test 1 yyy
is not a switch
Test 2 yyy
is not a switch

~: sh try_ash -yyy
Test 1 -yyy
is a switch
Test 2 -yyy
is not a switch

Using sh on a SUN yields:
1-chablis$ sh try_ash yyy
try_ash: bad substitution      

Pierre

********************
#This file checks if arg1 is a switch
b=${1%%-*}
echo Test 1 "$1"
if test -z "$b"
then 
 echo is a switch
else 
 echo is not a switch
fi

#Now it tries a direct test
echo Test 2 "$1" 
if test -z "${1%%-*}"
then 
 echo is a switch
else 
 echo is not a switch
fi