If you are wondering how can we check whether an environment variable is set or not in the system, here are few methods : 1. Manually a. Run “set” command on the shell prompt, it will list out all the variables set in the system : # set b. Run “echo” command on the shell to print the value of the environment variable : # echo $<environment variable> 2. Through Shell Script Let say we intent to check whether environment variable “envVar” is set or not? a. Method 1 – checking if “envVar” is set to “” (no value) : if [ "$envVar" == "" ] then echo “envVar is not set” else echo “envVar is set” fi b.Method 2 – checking if “envVar” is non NULL : if [ -n "$envVar" ] then echo “envVar has non NULL value, it is set.” else echo “envVar has NULL value, it is not set.” fi