How to import a variable from another script?

Question

I want to get a variable from another script, as demonstrated in this question on Stack Overflow:

How to reference a file for variables in a bash script

However, the answer uses the source command which is only available in bash. I want to do this in a portable way.

I have also tried

a.sh

export VAR="foo"
echo "executing a"

b.sh

#!/bin/sh
./a.sh
echo $VAR

But of course that does not work either. How to do this?

Answer 1

First of all, be aware that var and VAR are different variables.

To answer your question the . command is not bash-specific:

# a.sh
num=42

# b.sh
. ./a.sh
echo $num

The variables in "a" do not need to be exported.

http://www.gnu.org/software/bash/manual/bashref.html#Bourne-Shell-Builtins

Answer 2

Environment variables are only inherited from parent to child and not the other way round. In your example, b.sh calls a.sh, so a runs as a child of b. When a.sh exports var, it won't be seen by b.sh. Amend the logic so that the parent process exports the variable, e.g.

a.sh:

echo In a.sh...
VAR="test"
export VAR
./b.sh

b.sh:

echo In b.sh...
echo $VAR