add group if doesn't exist bash code example

Example 1: usermod: group 'sudo' does not exist

usermod - aG wheel username #in centos7

Example 2: bash if user exists in a group then add

egrep -i "^useraccount:" /etc/passwd;
if [ $? -eq 0 ]; then
   echo "User Exists"
else
   echo "User does not exist -- Invalid Username"
fi