Question

I’m having trouble using mutilple subprocess calls back to back.

These 2 work fine:

subprocess.call(["gmake", "boot-tilera"], cwd="/home/ecorbett/trn_fp")
p = subprocess.Popen(["gmake", "run-tilera"], stdout=subprocess.PIPE, cwd="/home/ecorbett/trn_fp")

However, I get an error when I try to run this call directly after:

time.sleep(10)
subprocess.call(["./go2.sh"], cwd="/home/ecorbett/trn_fp/kem_ut")

I added sleep in there because I need a few seconds before I run the “./go2.sh” program. Not sure if that is the issue.

Any advice?

Answer 1

A possible reason why your shell script is working on the command-line is that the shebang line was not written correctly (or not written at all). See an example in which the script would work from a command line but not as a Python subprocess: Is this the right way to run a shell script inside Python?

If your shell script did not have a shebang line specified, it would work from command line because $SHELL is set in your environment and the script is taking that as a default. When running from a python subprocess, python does not know what it is and fails with OSError: [Errno 8] Exec format error. The subprocess.call() to gmake worked because it is a binary program and not a shell script. Using the argument shell=True gave an instruction to interpret the argument exactly as it would in a shell.

However, be careful about using shell=True in subprocess.call() as it may be insecure in some cases: subprocess Python docs.