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Currently trying to pass a parameter from my python script to a bash script I created. How can I can get user input from my python script to my bash script?

This is the code for my python script 'passingParameters.py' which I used to try and send a variable (loop) to my bash script. I have tested this python script (after I adjusted the code) by sending the output to another python script which I used to read the input.

loop = str(sys.argv[1])
subprocess.check_call( ["./test.sh", loop], shell=True)

This is the code for my bash script 'test.sh'. I have tested this script by itself to confirm that it does receive user input when I just call the bash script from the command line.

echo "This number was sent from the passParameters.py script: " $1
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1  
Pretty related: How do I pass a Python Variable to Bash? – fedorqui Aug 5 '14 at 13:44
1  
The code should work. Do you get an error? Or why do you think the parameter isn't passed? – Aaron Digulla Aug 5 '14 at 13:57
    
@AaronDigulla no error, just the value I input into the command line doesn't show up – MarkOSullivan94 Aug 5 '14 at 14:27
    
@MOS182 See my comment to crono's answer. – chepner Aug 5 '14 at 14:32

1 Answer 1

up vote 4 down vote accepted

If you use shell=True then the executable is /bin/sh, which then calls test.sh but never sees the loop variable. You can either set shell=False and add the #!/bin/sh to the shell script,

#! /bin/sh
echo "This number was sent from the passParameters.py script: " $1

and

subprocess.check_call( ["./test.sh", loop], shell=False)

or pass the variable as a string:

subprocess.check_call( ["./test.sh %s" % loop], shell=True)

shell=True is not recommended anyway.

share|improve this answer
    
+1 It's not well documented, but combining your list of arguments with shell=True will result in the following command: sh -c ./test.sh <loop>. This will still run ./test.sh, but the argument loop is passed to sh as $0 rather than to ./test.sh as $1. – chepner Aug 5 '14 at 14:31
    
Thanks for your help! This first suggestion works fine. I tried the second suggestion with shell=True and it didn't work, says invalid syntax for the % beside loop. – MarkOSullivan94 Aug 5 '14 at 14:35
    
@chepner that's what I thought might have explained why it wasn't displayed so instead of having $1 in the bash script, I tried $0 and it still didn't print out anything. – MarkOSullivan94 Aug 5 '14 at 14:38

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