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new to python, i found that subprocess's check_output runs nicely on Windows but it seems to only run cmds that are in windows PATH env variable.

i can execute the following fine:

import sys
from subprocess import check_output

cmd = check_output("ipconfig", shell=True)
print(cmd.decode(sys.stdout.encoding))

and ipconfig output is displayed fine.

if i try run a specific command not in the path and try absolute path i get errors.

import sys
from subprocess import check_output

cmd = check_output("c:\\test\\test.exe", shell=True)
print(cmd.decode(sys.stdout.encoding))

Is there no way to use an absolute path reference for check_output? i was not finding any..

i even tried changing to that directory..

import sys
from subprocess import check_output
import os

os.chdir("c:\\test\\")
cmd = check_output("test.exe", shell=True)
print(cmd.decode(sys.stdout.encoding))

but i get the following error

File "C:\Python35\lib\subprocess.py", line 398, in run
    output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command 'naviseccli.exe' returned non-zero exit status 1

Process finished with exit code 1
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2
  • 1
    Apparently you managed to execute naviseccli.exe just fine, but it returned with non-zero exit status, which causes the CalledProcessError (which is the expected behaviour of check_output). Commented Apr 25, 2017 at 12:49
  • What errors do you get exactly when you do check_output("c:\\test\\test.exe", shell=True)? Commented Apr 25, 2017 at 12:50

2 Answers 2

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5

Popen offers a 'cwd' argument, that will execute in the defined directory:

import subprocess
cmd = subprocess.Popen('test.exe', stdout=subprocess.PIPE, stderr=subprocess.PIPE, cwd='C:/test', shell=True)

out, err = cmd.communicate()
print (out)

Using check_output:

subprocess.check_output('cd C:/windows && notepad.exe', shell=True)
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5 Comments

PERFECT ! thx , this got me what i wanted. i moved from .Net to python so it's such a diff world between the 2 LOL
I would expect an absolute path to an executable to always work, no matter what the current working directory is. Is this not the case in Python?
@mihca: Full path is always the best option.
Yes it works with absolute paths. But one has to use backslashes on Windows when combined with subprocess.run. Most Python API can handle forward and backward slahes (e.g. path.exsists), but apparently subprocess.run not. This was my issue.
Actually you can use forward slashes on Windows. All of the Windows API call handle them just fine. Subprocess.run works fine with forward slashes. What doesn't work is adding shell=True if your COMSPEC environment variable is set to the default cmd.exe. Powershell also accepts forward slash.
1

Please read about the documentation of CalledProcessError.

You can examine the output by catching this exception in a try ... except block and using the exception instance's output attribute.

try:
    ... ...                       # Running the command.
except CalledProcessError as cmderr:
    print (cmderr.output)         # Example of using the output.

In this way you can examine the failed command's exit status and output. I don't know what triggered the exact error, but it's unlikely a result of using the absolute path.

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