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I have a little test.sh script that I run from the command line ./test.sh and it will ask me for input to 2 questions that I enter, then it loops till I ctrl-c out of it.

I want to write a little python script that can run my test.sh, and enter the inputs to the script questions from variables, var1 and var2 that I set in python.

I also want to have another variable, var3, that loops for x long and runs my test.sh, and ends it then relaunches it every x minutes based on the value of var3

I wrote this code but it doesn't seem to pass the commands into my test.sh after it launches:

import os
os.system('./test.sh arg1')
time.sleep(10)
sh('input answer 1')
time.sleep(5)
sh('input answer 2')
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Read docs.python.org/3/library/subprocess.html notably about popen – Basile Starynkevitch 1 hour ago
1  
What does "then it loops" mean: it asks you 2 questions again or new input is not expected after the initial 2 questions? What does "loops for x long" mean: for x seconds or x times? – J.F. Sebastian 1 hour ago
1  
Is there some reason you don't want to do this in Python? – Tyler Crompton 51 mins ago
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2 Answers

up vote 2 down vote

Using pexpect:

import pexpect  # $ pip install pexpect

while var3:  # start ./test.sh again
    output = pexpect.run('./test.sh arg1', 
        timeout=x, 
        events={r'(?i)question 1': var1,
                r'(?i)question 2': var2, 
                pexpect.TIMEOUT: lambda _: True})  # exit after x seconds

Note: subprocess-based solution might be more complex due to buffering issues and it might require additionally pty, select modules, example.

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up vote 1 down vote 
import subprocess
p = subprocess.Popen('./test.sh arg1', stdin=subprocess.PIPE, stdout=subprocess.PIPE)

time.sleep(10)
p.stdin.write('input answer 1') #Probably adding \n is necessary
time.sleep(5)
p.stdin.write('input answer 2') #Probably adding \n is necessary

print p.stdout.readline() # To print one-line output of the shell script
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I think you mean p.stdout.readline() and p.stdin.write() ? – jdi 45 mins ago
There is no popen. It should be Popen. Also, see Q: Why not just use a pipe (popen())?. In addition your code might dead-lock if ./test.sh generates enough output (see appropriate warning in subprocess docs). – J.F. Sebastian 36 mins ago
@jdi, Thank you very much, these are errors of typing answer in Stackoverflow's editor :) – MostafaR 33 mins ago
@J.F.Sebastian Thank you very much, yes It's not a perfect solution, but I think sometimes we need easy and quick solutions. – MostafaR 32 mins ago
p.stdout.readline() will block forever if ./tesh.sh uses block-buffering for its output (default if stdout is a pipe). The reasons are explained in the link I've provided. – J.F. Sebastian 16 mins ago
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