Using if statements in bash to check if environment variables exist

This is a quick post to demonstrate how to use if statements in bash to check if we have the required environment variables in our environment before we continue a script.

Let's say we require FOO and BAR in our environment before we can continue, we can do this:

#!/usr/bin/env bash

if [ -z ${FOO} ] || [ -z ${BAR} ] ;
  then 
    echo "required environment variables does not exist"
    exit 1
  else 
    echo "required environment variables are set"
    # do things
    exit 0
fi

So now if FOO or BAR is not set in our environment, the script will exit with return code 1.

To test it, when we pass no environment variables:

$ chmod +x ./update.sh
$ ./update.sh
required environment variables does not exist

If we only pass one environment variable:

$ FOO=1 ./update.sh
required environment variables does not exist

And as the result we want, when we pass both required environment variables, we have success:

$ FOO=1 BAR=2 ./update.sh
required environment variables are set

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