Bash: change environment temporarily

Question

I am using a dev tool which supplies a script that sets environment variables. If I source the script the environment is modified for the duration of the bash secession. In order to revert the changes made by that script I need to restart the terminal. Is there a way to do it without restarting or opening new bash session?

Thanks.

Answer 1

Do it in a subshell:

$ (. /path/to/envsetup.sh; runtool)

If there's just a handful of environment changes, you can do them on the command line:

$ FOO=a BAR=b runtool # FOO and BAR will be set only for runtool

You can also use an actual subshell if you anticipate doing a number of things:

$ bash
$ : this is a subshell
$ . /path/to/envsetup.sh
$ thing1
$ thing2
$ : ...
$ exit
$ : this is the original shell

You may want to include $SHLVL in your $PS1 for the latter, so it's easier to tell that you're in a subshell. I also check for a (nonstandard) environment variable $PSYS and print it if set, as a sort of "label" for the environment.