Question

I’m reading Wrox, Beginning Linux Programming.
But I’ve got a question about shell variables.

Here is a shell script named test.sh:

#! /bin/bash
read test
echo $test
exit 0

Then I chmod the script:

$ chmod +x test.sh
$ ./test,sh

When I type “ok”, it echos the “ok”.

But when I returned to the shell interface, I typed:

$ echo $test

It returned nothing…

I don’t know why $test doesn’t return “ok” just like the script does…
And the book doesn’t metion it…

Thanks in advance:)

Answer 1

The variables only exist in the process where they were created (and also in child processes, if they are exported). Running a script creates a new process, after the script ends, all its variables are lost.

You can run the script without starting a new process by “sourcing” it:

. ./test.sh

You should remove the exit then, though, otherwise it will exit your current shell.