Python - Subprocess - How to call a Piped command in Windows?

echo, pipe, popen, python, subprocess

Solution

First and foremost, you don't actually need a pipe; you are just sending input. You can use subprocess.communicate for that.

Secondly, don't specify the command as a string; that's messy as soon as filenames with spaces are involved.

Thirdly, if you really wanted to execute a piped command, just call the shell. On Windows, I believe it's `cmd /c program name arguments | further stuff`.

Finally, single back slashes can be dangerous: `"\p"` is `'\\p'`, but `'\n'` is a new line. Use os.path.join() or os.sep or, if specified outside python, just a forward slash.

proc = subprocess.Popen(
    ['C:/Program Files/GNU/GnuPG/gpg.exe',
    '--batch', '--passphrase-fd', '0',
    '--output ', 'c:/docume~1/usi/locals~1/temp/tmptlbxka.txt',
    '--decrypt', 'test.txt.gpg',],
    stdin=subprocess.PIPE,
    stdout=subprocess.PIPE,
   stderr=subprocess.STDOUT,
)
stdout_value, stderr_value = proc.communicate('bosco')

Problem

How do I run this command with subprocess? I tried: ``` proc = subprocess.Popen( '''ECHO bosco|"C:\Program Files\GNU\GnuPG\gpg.exe" --batch --passphrase-fd 0 --output "c:\docume~1\usi\locals~1\temp\tmptlbxka.txt" --decrypt "test.txt.gpg"''', stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, ) stdout_value, stderr_value = proc.communicate() ``` but got: ``` Traceback (most recent call last): ... File "C:\Python24\lib\subprocess.py", line 542, in __init__ errread, errwrite) File "C:\Python24\lib\subprocess.py", line 706, in _execute_child startupinfo) WindowsError: [Errno 2] The system cannot find the file specified ``` Things I've noticed: - Running the command on the windows console works fine. - If I remove the ECHO bosco| part, it runs fine the the popen call above. So I think this problem is related to echo or |.

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