writing terminal output to file

Question

On my machine, I have some software which takes commands in the terminal and returns a list of values.

To run it, I have to type something like:

pdv -t filename

I am trying to run it as part of a python programme. When I run the following:

os.system('pdv -t %s' % (epoch_name))

then I get the values that I desire returned to my terminal (where epoch_name is the variable name for the filename). But when I try to write the result to a file:

os.system('pdv -t %s % "(epoch_name)" > 123.txt')

the file 123.txt is produced but it is empty.

I know that I am misplacing the " and/or ' characters, but I can't figure out where they should go.

Any help would be gratefully received!

score 9 · Answer 1 · answered Sep 06 '12 at 05:28

9

You can use subprocess.call, with the stdout keyword argument:

import subprocess

cmd = ['ls', '-l']

with open('output.txt', 'w') as out:
    return_code = subprocess.call(cmd, stdout=out)

answered Sep 06 '12 at 05:28

Warren Weckesser

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Oh I like that more than my solution. `with` rocks. +1 – tMC Sep 06 '12 at 05:33
Is that different than out=open('output.txt','w') ? – dooderson Sep 10 '14 at 18:53
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@user1311069: I used the context manager interface of the file object. See, for example, the first example here http://eigenhombre.com/2013/04/20/introduction-to-context-managers/ or here http://preshing.com/20110920/the-python-with-statement-by-example/ – Warren Weckesser Sep 10 '14 at 19:19
This worked but in the ipython notebook the terminal no longer pumps out information. Any idea why? – John M Mar 15 '15 at 00:22

score 5 · Accepted Answer · answered Sep 06 '12 at 03:50

I believe this does what you want. Argument to os.system() should be a string representing command to the OS.

os.system('pdv -t %s > 123.txt' % epoch_name)

There is subprocess module, which may worth look into if you are planning to process the output further in python.

score 4 · Answer 3 · answered Sep 06 '12 at 05:18

4

Its better to use subprocess module that os.system

import subprocess
subprocess.call(['pdv', '-t', filename, '>', dest_file_name])

answered Sep 06 '12 at 05:18

Rakesh

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tMC · Answer 4 · 2012-09-06T05:34:52.620

4

from subprocess import Popen
proc = Popen(['pdv', '-t', epoch_name], stdout = open('123.txt', 'w'))

edited Sep 06 '12 at 05:34

answered Sep 06 '12 at 05:26

tMC

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score 1 · Answer 5 · answered Sep 06 '12 at 03:36

1

See if the command script is available to you. It might do what you need.

answered Sep 06 '12 at 03:36

Jeremy J Starcher

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It is a unix/linux system command designed to capture console output of programs. – Jeremy J Starcher Sep 06 '12 at 03:45
I don't have easy access to an apple. Pull up a terminal and type `man script` and see what comes up. – Jeremy J Starcher Sep 06 '12 at 03:50

score 0 · Answer 6 · answered Jan 26 '15 at 10:27

Or you can use sys.stdout check this document from DiveIntoPython or the discussion here if it helps you out.

import sys

print 'Dive in'
saveout = sys.stdout
fsock = open('out.log', 'w')
sys.stdout = fsock
print 'This message will be logged instead of displayed'
sys.stdout = saveout
fsock.close()

writing terminal output to file

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