Capture return value from python script into shell script

Question

I have a shell script inside of which I am calling a python script say new.py:

#!/usr/bin/ksh

python new.py

Now this new.py is something like -

if not os.path.exists('/tmp/filename'):
    print "file does not exist"
    sys.exit(0)

If the file does not exits then the python script returns but the shell script continue execution. I want the shell script also to stop at that point if the file does nt exits and my python script exits.

Please suggest how can I capture the return in shell script to stop its execution further.

Keith · Accepted Answer · 2013-02-13 09:58:25Z

5

You need to return something other than zero from the exit function.

if os.path.exists("/tmp/filename"):
    sys.exit(0)
else:
    sys.exit(1)

The error value is only 8 bits, so only the lower 8 bits of the integer is returned to the shell. If you supply a negative number, the lower 8 bits of the twos complement representation will be returned, which is probably not what you want. You usually don't return negative numbers.

edited Feb 13, 2013 at 9:58

answered Feb 13, 2013 at 9:49

Keith

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2 Comments

Kundan Kumar Over a year ago

I am returning sys.exit(-100) now but in shell echo $? gives 155 ...is it like this number is assigned for these kind of error and can I use it safely like if $? != 0 then exit from the shell

Alex L Over a year ago

You could also do sys.exit(int(not os.path.exists("/tmp/filename"))), if you so desired

robertklep · Accepted Answer · 2013-02-13 09:53:00Z

5

if ! python new.py
then
  echo "Script failed"
  exit
fi

This assumes that the Python script uses sys.exit(0) when your shell script should continue and sys.exit(1) (or some other non-zero value) when it should stop (it's customary to return a non-zero exit code when an error occurs).

answered Feb 13, 2013 at 9:53

robertklep

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