How do I define a shell script variable to have scope outside of the script

Question

I'm using Ubuntu Natty.

I have a shell script which I have saved to /etc/init.d/qstart. The shell script contains the following:

apt-get -y update
apt-get -y upgrade
apt-get -y install tofrodos gcc make nmap lsof expect sysstat
dbpass="mydbpassword"

However, after I execute the script, I want to test that dbpass is set and I enter echo $dbpass in the prompt. But it's empty.

How do I define a variable in my shell script so that I can access it outside of it?!

Thanks in advance.

Answer 1

You can't set variables in parent process's environment. You can only set your current process's environment or prepare an environment for your process's children.

That said, you can instruct your shell to run commands from a script in the current shell process rather than forking a new shell. You can do it like this:

source your_script.sh

or

. your_script.sh

(note the space after the dot). Since here commands inside your_script.sh are run by the current shell the changes made to the environment inside the script are retained.

However, if the shell running your script is not an ancestor of the shell in which you wish to use the environment variable then there is no way to achieve your goal using environment variables at all. For example, if you script is run at initialization by some childless shell all environment settings done there are irreversibly lost forever. In this case, use some other mechanism like a file (perhaps somewhere under /var).

If you want all instances of a given shell to have certain variables set in their environment you can use initialization scripts that most shells use. Usually, they have a system-wide and per-user initialization scripts. For example, bash uses /etc/profile as system-wide initialization script for interactive login shell and $HOME/.bash_profile (also $HOME/.bash_login and $HOME/.profile) as per-user initialization script. See this reference for bash-specific details. If you use a different shell, try its respective manual.