CODEWITHSUNDEEP
pythonbashif-statementsubprocess
pidgey
pidgey

Reputation: 245

if statement in subprocess.Popen

I'm trying to run bash code via python. Normal statements (netstat, for example) work. If functions like the one below, however, don't. What should I change in order to run the following code correctly? Thanks in advance

>>> import os
>>> import subprocess
>>> 
>>> os.setenv['a']='test'
>>> _c = 'if [ "$a" == "test" ]; then echo $a; fi'
>>> print(subprocess.Popen(_c, shell=True, stdout=subprocess.PIPE).stdout.read().decode('utf-8'))
/bin/sh: 1: [: anto: unexpected operator

Upvotes: 0

Views: 2595

Answers (1)

sal
sal

Reputation: 3593

The command you are trying to run in the subprocess is following the bash shell syntax, where the string equality test is performed via ==. Now, on Unix with shell=True, the shell defaults to /bin/sh where instead the equality test is performed via a simple =. The two options you have here are:

  1. follow sh syntax in your script
  2. explicitly call '/bin/bash' as the executable to be run by adding executable='/bin/bash' to the Popen

As for option (1), replace _c as follows and it should work fine:

import os, subprocess
m_env = os.environ
m_env['a'] = "test"
_c = 'if [ "$a" = "test" ]; then echo $a; fi'
print(subprocess.Popen(_c, shell=True, stdout=subprocess.PIPE).stdout.read().decode('utf-8'))

That prints out "test".

Upvotes: 2

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