Posts tagged "processes" « SaltyCrane Blog

How to use the bash shell with Python's subprocess module instead of /bin/sh

Date: 2011-04-13 | Modified: 2011-04-16 | Tags: processes, python

By default, running subprocess.Popen with shell=True uses /bin/sh as the shell. If you want to change the shell to /bin/bash, set the executable keyword argument to /bin/bash.

Solution thanks this great article: Working with Python subprocess - Shells, Processes, Streams, Pipes, Redirects and More

import subprocess

def bash_command(cmd):
    subprocess.Popen(cmd, shell=True, executable='/bin/bash')

bash_command('a="Apples and oranges" && echo "${a/oranges/grapes}"')

Output:

Apples and grapes

For some reason, the above didn't work for my specific case, so I had to use the following instead:

import subprocess

def bash_command(cmd):
    subprocess ...

How to capture stdout in real-time with Python

Date: 2009-10-12 | Tags: notestoself, processes, python | 1 Comment

This solution is thanks to this article.

import subprocess

def myrun(cmd):
    """from http://blog.kagesenshi.org/2008/02/teeing-python-subprocesspopen-output.html
    """
    p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    stdout = []
    while True:
        line = p.stdout.readline()
        stdout.append(line)
        print line,
        if line == '' and p.poll() != None:
            break
    return ''.join(stdout)

How to get stdout and stderr using Python's subprocess module

Date: 2008-09-23 | Tags: processes, python | 5 Comments

I wrote previously about how to get stdout and stderr using os.popen4. However, per the Python documentation, using the subprocess module is preferred:

The subprocess module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. This module intends to replace several other, older modules and functions, such as:

os.system
os.spawn*
os.popen*
popen2.*
commands.*

See the subprocess module documentation for more information.

Here is how to get stdout and stderr from a program using the subprocess module:

from subprocess import Popen, PIPE, STDOUT

cmd = 'ls /etc/fstab /etc ...

How to use python and popen4 to capture stdout and stderr from a command

Date: 2007-03-12 | Tags: processes, python

You can use popen to capture stdout from a command:

import os
stdout = os.popen("dir asdkfhqweiory")
print stdout.read()

And your output will be something like:

>>> ================================ RESTART ================================
 >>> 
  Volume in drive C has no label.
  Volume Serial Number is XXXXXXXX
 
  Directory of C:\Python25
 
 
 >>>

If you wanted the error message, popen won't give it to you. To capture both stdout and stderr, use popen4:

import os

(dummy, stdout_and_stderr) = os.popen4("dir asdkfhqweiory")
print stdout_and_stderr.read()

This will give you the following output (which includes the error message):

>>> ================================ RESTART ================================
 >>> 
  Volume in drive C has no label.
  Volume Serial Number is ...

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