In Python3 using subprocess.Popen, I would like to capture the output and command return code for this "nc -z 192.168.25.14 22" command. Here is my sample code:
#!/usr/bin/env python
import urllib.request, urllib.error, urllib.parse
import subprocess
import time
# set up null file for pipe messages
nul_f = open('/dev/null', 'w')
# try loop for clean breakout with cntl-C
try:
with open('/mnt/usbdrive/output/Urls.txt') as f:
for line in f:
data = line.split()
commands = ['nc', '-vZ', data[1], data[0]]
print(commands)
try:
ncdmp = subprocess.Popen(commands , stderr=subprocess.PIPE, stdout=subprocess.PIPE,)
except OSError:
print ("error: popen")
exit(-1) # if the subprocess call failed, there's not much point in continuing
ncdmp.wait()
if ncdmp.returncode != 0:
print(" os.wait:exit status != 0\n")
else:
print ("os.wait:", ncdmp.pid, ncdmp.returncode)
print("STDERR is ", ncdmp.stderr)
print("STDOUT is ", ncdmp.stdout)
print("STDIN is ", ncdmp.stdin)
except KeyboardInterrupt:
print('Done', i)
# clean up pipe stuff
ncdmp.terminate()
ncdmp.kill()
nul_f.close()
and an example of the output is
*Commands is ['nc', '-vZ', '192.168.25.14', '22']
os.wait:exit status != 0
STDERR is <_io.BufferedReader name=12>
STDOUT is <_io.BufferedReader name=9>
STDIN is <_io.BufferedWriter name=8>*
I'm assuming that I have an error in my code or logic, but I can not figure it out. I have used similar code for other commands like ssh and ls without issues. For this "nc" command I get the same set of output/messages regardless of whether or not there is an open port 22 at the host address.
Thanks...RDK
OK, as I did not get any useful replies to this question, I changed the code from subprocess.Popen to subprocess.run as shown below. This modification worked for my requirements as ncdup.stderr contained the information I was looking for.
commands = shlex.split("nc -vz " + "-w 5 " + data[1] + " " + data[0])
try:
ncdmp = subprocess.run(commands , capture_output=True)
except OSError:
print ("error: popen")
exit(-1)
err_line = str(ncdmp.stderr)