Running shell script with no environmental variables

Question

As I know, newly running shell script inherits it's environment variables. Is there a way to block this? (running shell without variable inheriting)

score 25 · Accepted Answer · answered Sep 01 '10 at 14:13

25

It seems you can prefix your script with env -i which will clear the environment before running the script:

env -i sh test.sh

From man env:

-i, --ignore-environment
              start with an empty environment

Not sure why you would want to do this though...

answered Sep 01 '10 at 14:13

vmfarms

Thanks. This worked! I need this for calling build script in IDE without influencing IDE's configuration environmental variables. But still far away to goal. This may help your curiousness! – Eonil Sep 01 '10 at 14:24
To add another use case: I am currently evaluating fish and zsh as an alternative to bash. But I'm not quite ready to promote the candidate shell as my login shell (as in `chsh ...`. If I just open a terminal window and run `zsh` or `fish` (with or without `-l` doesn't matter) it pollutes my environment with all kinds of variables from the shell I started it. Doing the trick with `env -c` solves this problem for me. I do `env -i TERM=xterm-256color $(which fish)`. – Paidhi Feb 22 '12 at 19:33
1

This is useful if you have a cron task which is failing because the environment is not properly configured and you need to test it; also a good way to test if your scripts make assumptions about environment settings. Thanks! – razzed Aug 22 '13 at 04:21
1

Another possible place this could be useful is testing some periodic jobs (such as cron jobs) to ensure there are no environmental dependencies on the script. Same thing with commands that would be run in an "Exec" resource in a puppet manifest. – TommyTheKid Dec 16 '14 at 05:58

score 2 · Answer 2 · answered Sep 01 '10 at 14:14

2

One possibility (although it looks rather ugly):

exec -c $SCRIPT will start $SCRIPT with an empty environment. (see man bash search for exec \[-cl\]).

answered Sep 01 '10 at 14:14

weeheavy

1

This worked almost equally with env -i, however, I choose to use env -i because exec stops executing rest of script. – Eonil Sep 01 '10 at 15:26

2 Answers2