Set bash variables once before using across multiple scripts

Question

Let's say I have the following two commands:

A=1 B=2 C=3 run-app1.py
A=1 B=2 C=3 run-app2.py

I'd love to dry this out so I only need to update the variables in one place (and not risk them getting out of sync). Something like:

VALUES = get-values.sh

VALUES run-app1.py
VALUES run-app2.py

How can I do this?

This question is similar to: How to write a bash script to set global environment variable?. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem. — jonrsharpe
– jonrsharpe, Commented Sep 10, 2024 at 20:49
Write a script run_with_values which will invoke the passed as argument program with the values you want as in ./run_with_values run-app1.py — Eugene Sh.
– Eugene Sh., Commented Sep 10, 2024 at 20:52

Barmar · Accepted Answer · 2024-09-10 20:51:42Z

3

Export all the variables then run the scripts:

export A=1 B=2 C=3
run-app1.py
run-app2.py

answered Sep 10, 2024 at 20:51

Barmar

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5 Comments

chepner Over a year ago

If it's an issue, you can also do all this in a single subshell (export ...; run-app1.py; run-app2.py), which limits the scope of the environment changes.

Barmar Over a year ago

Yeah. I was kind of surprised you can't do that as a prefix, like A=1 { command1; command2; } or A=1 (command1; command2)

chepner Over a year ago

If I ever knew the rationale for restricting precommand assignments to simple commands, I've forgotten it.

John Bollinger Over a year ago

Yes. The POSIX shell language associates variable assignments specifically with simple commands, as it defines those, but makes no provision for doing the same with compound commands. The Bash manual is not clear on that, but its man page follows the POSIX wording pretty closely. I don't know the rationale, if any. Possibly contributing to confusion here is that redirections can be applied both to simple commands and compound commands, but the documentation provides for those two cases separately, not generically for all commands.

Barmar Over a year ago

I'm not surprised, shell syntax is kind of a mess, probably because it evolved organically.

Philippe · Accepted Answer · 2024-09-10 22:32:48Z

1

Try this :

vars=("A=1" "B=2" "C=3")
env "${vars[@]}" run-app1.py
env "${vars[@]}" run-app2.py

answered Sep 10, 2024 at 22:32

Philippe

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