UNIX for Dummies Questions & Answers

Hi All

In a script, I want a user to enter 4 characters, these can be a mix of letters (uppercase and lowercase) and numbers.

In this example $var represents what the user has entered.

eg $var can be A9xZ, 3DDL, bbHp .........etc

I need to check that the user has only entered characters so I added the following code:

# Check for invalid characters
echo "$var" | grep [^a-zA-Z0-9] >/dev/null
if [ $? -eq 0 ]
then
echo "$var is not valid."
fi

This appears to work ok unless the user enters a wildcard character.

For example if the user enters bin*, the script expands the * and makes $var equal to all files in the current directory which start with bin.

So $var is "bin bindir binary"

My question is how can I process $var literally as "bin*" in the above grep statement?

Thanks for your help
Helen

Change this line in your code from:

echo "$var" | grep [^a-zA-Z0-9] >/dev/null

to:

echo "$var" | grep "[:alnum]\{4\}">/dev/null

Thanks for your reply Photon, I'll give it a try