python - 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!

Answer 1

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)

Answer 2

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.

Answer 3

Its better to use subprocess module that os.system

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

Answer 4

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

Answer 5

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

Answer 6

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()