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
call(['ls', '-l'])

How do I save this output to a file, or put it into lists or sets?

[-rw-r--r--]  [1] [name]  [staff]   [426] [14 Jan 21:52] [HelloWorld.class]
[-rw-r--r--@] [1] [name]  [staff]   [107] [14 Jan 21:51] [HelloWorld.java]
...
etc.

I want to be able to access particular information directly, and then add it to the set, but I do not know how many items will be listed.

Any hints, snippets, or examples would really help.

Answer 1

With >= python3.5 you can use subprocess.run :

ls_lines = subprocess.run(['ls', '-l'], stdout=PIPE).stdout.splitlines()

With >= python2.7 or >= python3.0 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

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>'}

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

People have already responded to it. Nevertheless, just in case somebody needs it

import subprocess
output_list=subprocess.check_output(['locate','*.nse']).decode('utf-8').split('\n')[:-1]

Answer 6

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

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