A common problem in the UNIX and Linux worlds is managing the shell profile. The profile is used by the shell to set basic parameters such as environment variables that all programs running under the shell would have access to. An example is the OPENMAKE_SERVER environment variable that must have as its value the URL of the KB server servlet.

Profiles tend to grow and may contain a number of different settings important to different programs. It is very common to hear about changes to the profile causing some unintended effect to one or more settings, which in turn causes some program or other to stop working. For example, if I have an OpenMake client installed on a Linux box, and then I want to use a COBOL compiler, I may need to set a number of new variables like COBDIR in my profile. A common practice would be to copy the profile from one of the developers who regularly compiles COBOL, on top of your profile. This way you ensure your compiles work. However, by copying you just overwrote all the setting you had before.

Now, of course, you wouldn’t intentionally lose all your settings you careful defined, but maybe the sys admin copied it for you, trying to be helpful. This very simplistic example is easy to handle, but with lots of settings and lots of programs depending on them, you could easily have a situation where some parameter change is not detected until something crashes in production. So, what do you do? You want to test your changes, but the profiles are usually in some shell script language and are outside the common application lifecycle processes.

It turns out Perl is ideal for this task. All you have to do (for a login-type profile) is to check the environment variables. This effectively gives you both functional and regression tests for your profile.

use Test::More;

ok( exists $ENV{COBDIR}, "COBDIR exists");

ok($ENV{COBDIR} eq '/usr/cob', "COBDIR set correctly");

Because it is so easy to write these tests (vi: yy j p dw <your change>), I like to make them pretty granular. In this example, I will know from the two tests if COBDIR is set incorrectly, or not set at all. That can tell me a lot about what caused the problem. This is an incredibly small investment to ensure your profile changes don’t cause unintended production failures.