从python调用时挂起shell脚本

Question

python pythontop.py # Hangs in test.sh. cat of urandom is not truncated at all

pythontop.py

import subprocess
subprocess.call(['test.sh'])

test.sh

RAND=`cat /dev/urandom | tr -dc 'a-zA-Z0-9'| fold -w 10 |  head -n 1`

EDIT:Folks apologies for any confusion. It turns out simply calling the shell script from python itself causes the script to hang.
UPDATE: More update. If I insert a tee before head. I get a broken pipe message. Which means head did its job. Got a line and closed the file.
cat /dev/urandom | tr -dc 'a-zA-Z0-9'| fold -w 10 | tee | head -n 1
I see the script still hung even after the broken pipe message!
UPDATE: Folks, I find this easily recreatable in linuxcontainers.org machine. I did this so that those reading this question can confirm this observation with their own experiments. Since this seems a little too hard to be true. https://linuxcontainers.org/lxd/try-it/

Answer 1

Although your code works just fine for me on my laptop, it seems to hang in a containerized environment, such as linux containers .

Changing

subprocess.call(['test.sh'])

to

subprocess.call(['/bin/bash', 'test.sh'], shell=True)

stops the script from hanging.

The subprocess documentation advises against using shell=True on arbitrary unsanitized input from untrusted sources, so you have been warned.