How to set a variable's value from job output

Question

Can anyone point me at documentation on how to set the value of a variable based on the output of a job? We are running TES v6.0.2.153.
The Agent/Adapter is a Linux command line, so the Command could be for example:
echo foo
and I would like a variable named bar to contain the value foo.  (Obviously in real life the variable value would be dependent on what the command output)
Thanks in advance,
Martin

Answer 1

One more nugget: to parse the response from a command from a UNIX/Linux agent for a specific string and store that in a variable, I followed Rami's advice and then had to find the string in the output.
The below example puts the first digit of a random number in the variable:
Job Command:
bash -c
Command Parameters:
"'echo' Random number is $RANDOM | perl -ple 's/.*Random number is (\d{1}).*/\1/'"
Note that your command itself (in this case "echo") cannot be put in the Command box, otherwise TES does not interpret the Command Parameters correctly.  So you need to set the Command to "bash -c" (run the command in the parameter string), and enter your command and parameters within double quotes in the Command Parameters, with the command being run (in this case "echo") in single quotes at the beginning.
(I also had to make my .bash_profile run without any output to avoid it being prefixed to the variable value.)
Hope this helps,
Martin.