python subprocess output to list or file

Question

I want to run the following bash command in Python 3:

ls -l

I know that I can do the following:

from subprocess import call         


        

Answer 1

With python2.7 you can use subprocess.check_output:

ls_lines = subprocess.check_output(['ls', '-l']).splitlines()

Prior to python2.7, you need to use the lower level api, which is a bit more involved.

ls_proc = subprocess.Popen(['ls', '-l'], stdout=subprocess.PIPE)
ls_proc.wait()
# check return code
ls_lines = ls_proc.stdout.readlines()

Answer 2

from subprocess import Popen, PIPE
output = Popen(['ls', '-l'], stdout=PIPE).communicate()[0]

You can then do whatever you want with the output. See python docs for detailed documentation

Answer 3

If what you really want is to list a directory, rather use os.listdir

import os
files = os.listdir('/path/to/dir')
for file in files:
    print(file)

Answer 4

Read about Popen. the set you asked for you get with

import subprocess
proc = subprocess.Popen(['ls','-l'],stdout=subprocess.PIPE,stderr=subprocess.PIPE)
myset=set(proc.stdout)

or do something like

for x in proc.stdout : print x

and the same for stderr

you can examine the state of the process with

proc.poll() 

or wait for it to terminate with

proc.wait()

also read

read subprocess stdout line by line

Answer 5

One way to access to the information in ls -l output is to parse it. For example, csv.DictReader could be use to map each column to a field in a dictionary:

import subprocess
import csv

process = subprocess.Popen(['ls', '-l'], stdout=subprocess.PIPE)
stdout, stderr = process.communicate()

reader = csv.DictReader(stdout.decode('ascii').splitlines(),
                        delimiter=' ', skipinitialspace=True,
                        fieldnames=['permissions', 'links',
                                    'owner', 'group', 'size',
                                    'date', 'time', 'name'])

for row in reader:
    print(row)

The code above will print a dictionary for each line in ls -l output such as:

{'group': '<group_name>',
 'name': '<filename>',
 'links': '1',
 'date': '<modified_date>',
 'time': '<modified_time>',
 'owner': '<user_name>',
 'permissions': '-rw-rw-r--',
 'size': '<size>'}