Shell Programming and Scripting

Hey, I've create a custom useradd script, and I don't want the person creating the user to be able to put comma's in any of the input fields, because it could corrupt the /etc/passwd file.

I don't care what other characters they put in there, so is there a way I can just check all the input for comma's only, and if they are are there, just strip them out? Or replace them?

Thanks.

Code:

for d in $@
do
    case $d in
    *,* )
        echo comma found
        ;;
    * )
        ;;
    esac
done