Bash script to set an environment variable if unset [duplicate]

Question

I wrote a bash script to set the environment variable VAR if it is currently not set:

example.sh

#!/bin/bash

if [ -z $VAR ]; then
    export VAR=abc
fi

Now I type this in the command line: ./example.sh && echo $VAR. I expect abc, but the result is blank. Why?

You must run it as source ./example.sh && echo $VAR. Your command sets the environment variable within the context of example.sh script (which runs in a subshell): this cannot affect the parent environment. — M. Nejat Aydin
– M. Nejat Aydin, Commented Feb 6, 2023 at 9:02
As an aside, you must quote your variable to prevent globbing and word splitting: [ -z "$VAR" ] and echo "$VAR". — M. Nejat Aydin
– M. Nejat Aydin, Commented Feb 6, 2023 at 9:09

akathimi · Accepted Answer · 2023-02-06 09:02:54Z

2

Use source example.sh or . example.sh

answered Feb 6, 2023 at 9:02

akathimi

1,6112 silver badges11 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1