Regular expressions

[Christer Hermansson]

Hi.

I'm trying to use regular expressions inside a shell script (/bin/sh) on 
my freebsd box and can't get it to work so I searched the web  and found 
http://regexlib.com/RETester.aspx

On this webpage I could test my pattern "^[A-Za-z0-9_-]+$" and 
everything was fine, did exactly what I wanted to do, check that a 
string only contains some combination of the characters A-Z, a-z, 0-9, 
hyphen - and underscore _.

I also found some basic example at 
http://www.grymoire.com/Unix/Sh.html#uh-88 :

--------8<--------8<--------8<--------8<--------8<--------

#!/bin/sh

echo "Type in a number"
read ans
number=`expr "$ans" : "([0-9]*)"`
if [ "$number" != "$ans" ]; then
echo "Not a number"
elif [ "$number" -eq 0 ]; then
echo "Nothing was typed"
else
echo "$number is a fine number"
fi

--------8<--------8<--------8<--------8<--------8<--------

The above example doesn't work on my freebsd box. Maybe I need to update 
my system, sitting with 6.0R which never been updated.

Is there anyone who has some advice about how to get regular expressions 
to work in FreeBSD shell script ?

-- 

Christer Hermansson