Python version: '2.6.5 (r265:79063, Oct 1 2012, 22:07:21) \n[GCC 4.4.3]'
I have this:
>>> ss = subprocess.call("ls -z", shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE) How do I get the error message now ?
This does not work:
>>> for i in subprocess.PIPE: ... print i ... Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'int' object is not iterable That combo of options doesn't work very well. Communicate() will read stdout, stderr and wait for the program to terminate.
proc = subprocess.Popen("ls -z", shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE) out, err = proc.communicate() assert proc.returncode == 0, 'i am sad' print out print err If you want to read stdout line by line as the program runs, you can create your own thread to babysit stderr or pipe stderr to stdout.
subprocess.PIPE is just a magic constant that tells the subprocess functions "create a new pipe and use it here" when you pass it. (It happens to be -1, but that's not important.) So, iterating that magic constant won't do anything useful.
shell=Trueand"ls -z"instead of["ls", "-z"]? It's not relevant to your problem, but generally, using the shell when you don't need to is a bad idea, as is passing command lines and hoping you got the escaping right so they get parsed into the list you had in mind.