CODEWITHSUNDEEP
pythoncommand
Amritha
Amritha

Reputation: 815

which command equivalent in Python

I have the following code which i am using to check if the program class-dump exists on a system. The program only returns a blank.

cmd = ["which","class-dump"]
process =  subprocess.Popen(cmd, stdout=subprocess.PIPE)
print process.stdout.read()

This code always returns a blank. Technically it should work right ?

Upvotes: 1

Views: 572

Answers (5)

wberry
wberry

Reputation: 19367

This code does the same thing as the shell which command programatically, except that it does not "find" symbolic links. To support that, you can enhance the isx function.

import os.path, itertools
isx = lambda program: lambda folder: (lambda p: \
    os.access(p, os.X_OK) and os.path.isfile(p))(os.path.join(folder, program))

def which(program):
  try:
    return itertools.ifilter(isx(program), os.environ['PATH'].split(':')).next()
  except StopIteration:
    raise ValueError, 'no executable file named %s found in search path' % (program,)

Example use:

>>> which('ls')
'/bin'
>>> which('foo')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in which
ValueError: no executable file named foo found in search path

Upvotes: 0

spicavigo
spicavigo

Reputation: 4224

I tried the following on my machine and its working perfectly.

import subprocess
cmd = ["which","java"]
process =  subprocess.Popen(cmd, stdout=subprocess.PIPE)
print process.communicate()

this is the output

('/usr/bin/java\n', None)

Upvotes: 2

rplnt
rplnt

Reputation: 2409

which is a shell built-in. You need to pass shell=True to the Popen.

Upvotes: 1

C&#233;dric Julien
C&#233;dric Julien

Reputation: 80801

Hmmm, it looks like the class-dump does not exists (in the PATH used by your python interpreter)

Upvotes: 0

Geo
Geo

Reputation: 96897

Does it work if you use communicate instead? See this warning:

Warning

Use communicate() rather than .stdin.write, .stdout.read or .stderr.read to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process.

Also, is it possible that your script runs under another PATH than your shell? Dump os.environ["PATH"] and check.

Upvotes: 0

Related Questions