BASH: Accessing the value of the name of an environment variable passed in $1

[fishjie]

Hi, doing exercises in A Practical Guide to Linux Commands, Editors, and Shell Programming by Mark G. Sobell. One of the exercises involves a script that is passed in the name of an environment variable.

So lets say I have an environment variable $test that I exported with value "testing".

So lets say the script is named foobar, and is invoked:
foobar test

So now the environment variable name test is in $1. But how do I access the actual value of $test, which is "testing", in bash? I tried doing something like:

value=$("echo \$$1")

which seems way too hackish. Am I missing something simple here?

Also, later, the script adds some values to this $test environment variable how do I export the new $test variable value in bash?

[Lakshmipathi]

Try using

printenv $1

in your script.

[deepak.pesumalani]

I have tried this on my machine in following way.

Environment variable is PATH and its value is "/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin"

Script temp.sh
=======================
echo "======"
echo $1
echo "======"
temp=$1
echo "======"
echo $temp
=======================

Invoke as

sh temp.sh $PATH

O/P is

======
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin
======
======
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin

[fishjie]

Thanks, that works when the variable is passed in as $PATH. Now what if in the script, I modified the value, and wanted to export those changes to $PATH. How would I do that? In your example the value of $PATH that gets passed in, so how would I go about exporting it back out to PATH?

In case anyone is wondering, the exercise is to write a bash script that takes in two arguments, name of environment variable, and name of value to append to environment variable if it doesn't already exist in the list. I've gotten the appending part down, I just need to figure out how to export the value once its appended. Its tricky because the environment variable itself is one of the arguments.