os.system() execute command under which linux shell?

Question

I am using /bin/tcsh as my default shell.

However, the tcsh style command os.system('setenv VAR val') doesn't work for me. But os.system('export VAR=val') works.

So my question is how can I know the os.system() run command under which shell?

Answer 1

These days you should be using the Subprocess module instead of os.system(). According to the documentation there, the default shell is /bin/sh. I believe that os.system() works the same way.

Edit: I should also mention that the subprocess module allows you to set the environment available to the executing process through the env parameter.

Answer 2

os.system() just calls the system() system call ("man 3 system"). On most *nixes this means you get /bin/sh.

Note that export VAR=val is technically not standard syntax (though bash understands it, and I think ksh does too). It will not work on systems where /bin/sh is actually the Bourne shell. On those systems you need to export and set as separate commands. (This will work with bash too.)

Answer 3

If your command is a shell file, and the file is executable, and the file begins with "#!", you can pick your shell.

#!/bin/zsh
Do Some Stuff

You can write this file and then execute it with subprocess.Popen(filename,shell=True) and you'll be able to use any shell you want.

Also, be sure to read this about os.system and subprocess.Popen.