At 12:04 PM 8/18/2007, Christer Hermansson wrote:

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

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 :



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"
echo "$number is a fine number"


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

You have a syntax error using expr. Do a man on expr for more details but if you change that line from:
number=`expr "$ans" : "([0-9]*)"`
number=`expr "$ans" : "\([0-9]*\)"`

You will get the desired results.

Also when debugging scripts remember to add:
set -x
to your script on the second line, and see what the script lines are actually doing.


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