grep: should report the bad regex

[Aharon Robbins]

Greetings.  Using GNU grep 2.5.1, if you give an invalid regex, all grep
does is tell you that it got a bad regex, but it doesn't print the
regex back at you.  This is not a problem when you enter the grep command
straight at the command line, but is a problem if you build it on the fly
using a shell loop like this:

        while read com
        do if grep -q "<literal>$com</" file.xml
           then echo $com
           fi
        done < bigcomlist > smallcomlist

Thanks,

Arnold Robbins