Survival of manually edited variables

Question

I have some environmental variables set in my .profile, and thus the variables can be set automatically when I log in. In some special cases, I also need to change some settings using the command "export", just like:

export OMP_NUM_THREADS=3

When I manually edit an environmental variable, run a software which requires the variable with nohup, and then log out. Does the variable turn back at the moment I exit?

You login again and see if the variables have the value you set? O.o — muru, May 26 '16 at 03:59
It turns back to the value that I set in my .profile, but I don't know what the value is when I am not on server... — Ezekiel Kuo, May 26 '16 at 04:11

score 0 · Answer 1 · edited Apr 13 '17 at 12:24

For the program that you started with nohup, no, the variable won't be reset because you logged out (unless it's a program that watches for you logging out and then resets the variable, or some such weirdness).

Each process has its own copy of environment variables. For a process X, other processes cannot typically change X's copy of variables without X's cooperation. This is also why a script cannot change the current shell's variables unless it is sourced.

So, once you start the process, it gets a copy of OMP_NUM_THREADS. What you then do in your shell (including setting OMP_NUM_THREADS to another value, logging out, starting another shell, sacrificing to Cthulhu) won't affect X's environment variables.

Survival of manually edited variables

1 Answers1