2

I am using subprosess to ping a server, but I want to receive the full response. In the past I have used os to ping but this only returned 1 or 0.

The code that I am using is:

import subprocess
p = subprocess.Popen(['ping', '8.8.8.8'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = p.communicate()
print out

I would like if if the response that I would see if I had ran it from the terminal was visible. Please note that I am using -c and not -n because I am using linux as the OS.

I am confused as to why this does't work because when I ran similar code, it printed out the expected response:

import subprocess
p = subprocess.Popen(['ls', '-a'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = p.communicate()
print out

The code above printed out the list of files and folders in the directory which the python script was saved in, so the code that I am using seems to be correct.

My question is, how can I have the response from pinging a server assigned to a variable that I can then print out like I can when I run ls.

jfs
  • 399,953
  • 195
  • 994
  • 1,670
Kian Cross
  • 1,818
  • 2
  • 21
  • 41

2 Answers2

3

The default ping is a continuous process; it doesn't stop until you interrupt it, e.g. with ctrl-C. Of course, with subprocess, ctrl-C is not possible.

subprocess.communicate will buffer all the output in memory until the program ends (that is, never); you could use it in fact to create an out-of-memory error ;-).

If you just like a few pings, or even 1 ping, use the -c option to ping:

p = subprocess.Popen(['ping', '-c1', '8.8.8.8'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)

If you'd like continuous polling, you could wrap this in a while loop inside Python.

  • it is incorrect. It is possible to [emulate Ctrl+C with subprocess](http://stackoverflow.com/a/28387508/4279) – jfs Feb 07 '15 at 21:18
  • @J.F.Sebastian Neat; though I guess it's not directly the most obvious way to do this. –  Feb 08 '15 at 03:01
1

.communicate() waits for the child process to finish. ping with the given arguments does not exit unless you explicitly stop it e.g., send it Ctrl+C.

Here're varous methods to stop reading process output in Python without hang.

If want to see the output while the process is still running; see Python: read streaming input from subprocess.communicate()

Community
  • 1
  • 1
jfs
  • 399,953
  • 195
  • 994
  • 1,670