How to code output of another script as an in condition in some other script

Question

I have an python script which gets input from arguments. can I place this as an condition in if statement of bash script ? If python script ends with an error (exit 1) it has to trigger another python script and if python script ends with 0 then no action required. I thought to do it via if condition in bash script. I am erroring out in the code.

#!/bin/bash

if [ "python pythonscript.py argument" == 1 ]; then
 python pythonscript2.py argument
fi

exit 0

Same argument is passed to both python scripts. argument is a string like something_Dept-envi. I get nothing when I execute above no syntax error at the same time nothing happens

#!/bin/bash

if [ "python pythonscript.py argument" == 1 ]; then
 python pythonscript2.py argument
fi

exit 0

If python script ends with an error (exit code 1), i want another python code to be executed with argument else exit o

William Pursell · Accepted Answer · 2019-04-15 14:33:38Z

1

Stop thinking of [ as an operator. It's just a command. But in this case, you don't want to use it; you just want to call your python script:

if python pythonscript.py argument; then
    echo executed when python return 0
else
    echo executed when python returns non-zero
fi

For your particular case, you just want:

if ! python pythonscript.py argument; then
    python pythonscript2.py argument
fi

This only distinguishes between an exit with zero or non-zero, and does not check for the particular non-zero value. If you want to do something different when the script exits with a 2 than it does when it exits with a 1, you can check the value of $?, but you're better off not doing that.

answered Apr 15, 2019 at 14:33

William Pursell

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3 Comments

Randy Ren Over a year ago

Hi - I will be wanted to check for exit code 2 alone. I am not bothered about exit code 1, if the python script ends with 1 I am fine with it and believe it will exit. But I wanted to check for exit code 2, wanted to trigger another script if 0 do nothing just exit. I am worried on seeing your statement 'but you're better off not doing that'. Is it tough to do it that way ? Any information will help.

William Pursell Over a year ago

You can do python pythonscript.py argument; case $? in 1) ...;; 2) ...;; *) ...;; esac, but IMO that is an anti-pattern.

Randy Ren Over a year ago

oh ok. Thanks for that info. I will try that.

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