CODEWITHSUNDEEP
pythonlinuxpython-2.7shell
R. T.
R. T.

Reputation: 23

Interactive shell program wrapper in python

I'm trying to run a shell program through python. I need to run a command, then while it's still running and waiting for input to continue, I need to take the output received by the program, and process that data as a string. Then I need to parse some data into that program, and simulate an enter pressing. What would be the best way to achieve this?

Upvotes: 2

Views: 1634

Answers (2)

wildwilhelm
wildwilhelm

Reputation: 5019

subprocess.Popen will work for this, but to read and then write and then read again you can't use communicate (because this will cause the process to end).

Instead, you'll need to work with the process's output pipe (process.stdout below). This is tricky to get right, because reading on the process's stdout is blocking, so you sort of need to know when to stop trying to read (or know how much output the process is going to produce).

In this example, the subprocess is a shell script that writes a line of output, and then echoes whatever you give it until it reads EOF.

import subprocess

COMMAND_LINE = 'echo "Hello World!" ; cat'

process = subprocess.Popen(COMMAND_LINE, shell=True,
                           stdin=subprocess.PIPE,
                           stdout=subprocess.PIPE)

s = process.stdout.readline().strip()
print(s)
s2 = process.communicate(s)[0]
print(s2)

Gives:

Hello World!
Hello World!

For more complicated cases, you might think about looking at something like pexpect.

Upvotes: 1

Iskren
Iskren

Reputation: 1341

Use subprocess.Popen to run your shell application and use communicate to interact with it.

Upvotes: 1

Related Questions