Question

In Python, we can use “import” to import the names of another namespace into the current namespace.

Similarly, is there a notion like “namespace” in existence in UNIX shell scripting at all? If so, then does Cygwin (or an actual UNIX shell) have some command to import names from another namespace to the current namespace, as in Python? Thanks.

Note to the community members with admin priviledges: I really think this question IS a programming question instead of a “superuser” question. Please kindly elaborate on why if you disagree with that. Thanks a lot for your time.

Answer 1

There is no way to do exactly what you are asking for.

The source envFile command and it’s alternate . envFile can be very helpful.

envFile file will just be a list of environment assingments.

FrontOfficeSystem=MyFrontOffice
BackOfficeSystem=myBackOffice

When you include the command in your script to ‘source’ the envFile (any name will work), the shell reads the code as if it was directly in your main shell script. Like ‘include’ in a lot of langauges. But namespaces, … nope. See next.

More helpful : see indirect references in advanced Bash scripting, this is probably better than using eval ... (per below), but I haven’t had the opportunity to work with it.

finally, you may also benefit from eval and varname indirection, i.e.

 src=FrontOffice
 eval \$${src}System="${src} has data"

 src=BackOffice
 eval \$${src}System="${src} has data"

Not a great example, but I don’t have access to the scripts where I really went to town on this idea. It helped me genericize (sp) some code that otherwise would have had to be repeated 10 times, for each data src (I put the repeating block of code in a for loop, with the src names as the element list for the for(each), then the eval would expand ${src}System as FrontOfficeSystem, BackOfficeSystem). If you windup with spaces in your values for your src list, then all bets are off.

use set -vx in your terminal window and copy/paste above code to see how it works. It might help.

I hope this helps.

P.S. as you appear to be a new user, if you get an answer that helps you please remember to mark it as accepted, and/or give it a + (or -) as a useful answer.