Regex

Introduction

Let’s say we want to change our git username to another one. Instead of checking manually if the username is already taken, we can automate this process by writing a script named fgitusr. The content of the script looks like this:

Code

# Check regex rules
if [[ !("$1" =~ ^[0-9a-zA-Z]{1}[0-9a-zA-Z\-]*[0-9a-zA-Z]{1}$) ]]; then
    echo "$1 DOESN'T MATCH REGEX"
    exit 1
fi

# Check if usersname exists
curl --output /dev/null --silent  --head --fail "https://github.com/$1"
if [ $? -eq 0 ]; then
    echo "USER $1 EXISTS";
else
    echo "USER $1 DOESN'T EXIST";
fi

The main idea is that we use curl to look if the url https://github.com/<username> is a valid link. If it is, then the user exist.