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I would like to capture some characters following a word in a string. For example, 

Pinging 10.1.1.1 with 32 bytes of data:

Reply from 10.1.1.1: bytes=32 time=39ms TTL=253

Reply from 10.1.1.1: bytes=32 time=17ms TTL=253

Reply from 10.1.1.1: bytes=32 time=17ms TTL=253 

Reply from 10.1.1.1: bytes=32 time=17ms TTL=253

Ping statistics for 10.1.1.1:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds:
    Minimum = 17ms, Maximum = 39ms, Average = 22ms

I would like to get characters following time= but stopping the space before TTL for the first instance of time=

I know I can do a split to time= and get the characters which follow but I don't know how to have it stop before the TTL (the number could be more than 2 digits for instance, so just getting the 4 which follow isn't an option)

Perhaps regex would also be an option? I've seen something like (?:time=).* would get the first instance but, again, i'm uncertain how to specify it to stop after the ms.

Edit - Added final code now that it is working. Thanks for all the help!

import os
import subprocess
import re

#Define Target
hostname = raw_input("Enter IP: ") 

#Run ping and return output to stdout.
#subprocess.Popen runs cmdline ping, pipes the output to stdout. .stdout.read() then reads that stream data and assigns it to the ping_response variable
ping_response = subprocess.Popen(["ping", hostname, "-n", '1'], stdout=subprocess.PIPE).stdout.read()

word = "Received = 1"



latency = 1

p = re.compile(ur'(?<=time)\S+')
x = re.findall(p, ping_response)

if word in ping_response:
print "Online with latency of "+x[0]

else:
print "Offline"

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4
  • how are you running the ping? Commented May 1, 2015 at 17:56
  • @PadraicCunningham I added the code I am using to the question. Thanks! Commented May 1, 2015 at 18:01
  • @PadraicCunningham Yes. Commented May 1, 2015 at 18:14
  • Ok, was going to say you could grep the output, since it is windows an easier way would be to simply use check_output Commented May 1, 2015 at 18:14

3 Answers 3

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4

Try this RegEx

(?<=time=)\S+

This should do it with re.findall for you.

See demo here

import re
p = re.compile(ur'(?<=time=)\S+')
test_str = u"\n\n Pinging 10.1.1.1 with 32 bytes of data:\n\n Reply from 10.1.1.1: bytes=32 time=39ms TTL=253\n\n Reply from 10.1.1.1: bytes=32 time=17ms TTL=253\n\n Reply from 10.1.1.1: bytes=32 time=17ms TTL=253\n\n Reply from 10.1.1.1: bytes=32 time=17ms TTL=253\n\n Ping statistics for 10.1.1.1: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 17ms, Maximum = 39ms, Average = 22ms\n"     
re.findall(p, test_str)
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6 Comments

@BhargavRao hi!!!!!!!!!! yups!!!! long trip :P........ stackoverflow.com/questions/29988595/… see dis!!!!!!! brilliant answer by Anti happala.......There's always something to learn from SO !!!!!!!!
If I have my sample string (the one starting with "Pinging") in a variable called ping_response, for the line where you start [test_str = u"\n\n ..."] would I just put [test_str = u ping_response] ?
How do I then output that data? I have {p = re.compile(ur'(?<=time=)\S+') re.findall(p, ping_response) if word in ping_response: print "Online with latency of %s" % ?????}
@Abraxas use x=re.findall(p, test_str) x will be list of all times
@Abraxas (?<=time[<=])\S+
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1

Use a regexp but keep it simple: Instead of lookaheads/lookbehinds, do it the old-fashioned way with capturing groups:

>>> times = re.findall(r"time=(.*?) ", pingdata)
>>> times
['39ms', '17ms', '17ms', '17ms']

Explanation: .*? is a non-greedy regular expression, so it will stop as soon as a space matches after the parens. That matches exactly what you want. re.findall() with a capturing expression will return what matches inside the parens, not the entire match.

If you only want the first match (as you say in your question, I now notice), take times[0] or use re.search instead, which returns the first match (but as a match object, so you extract the captured group).

>>> m = re.search(r"time=(.*?) ", pingdata)
>>> m.group(1)
'39ms'
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8 Comments

As I am very new to this could I verify that 'pingdata' is the variable my string of the ping response is and then clarify how I would present this number in my response (ie: [print "Online with latency of %s" % latency] would latency = m.group(1)?
Yes, pingdata is a string containing the entire ping response. m.group(1) is also a string, so you can use it as you suggest (or simply "Online with latency "+m.group(1))
You are welcome. PS. If you're just getting started, I suggest upgrading to python 3. It's very mature and well-supported by now, there's no reason to work with python 2 unless you have no choice for some reason.
I am a little bit of the way in to Zed Shaw's book "Learn Python the Hard Way" and he actually said the opposite but I am glad to hear a differing opinion. I'm just hoping to become competent with some scripting and programming to aid in my sysadmin work. I'll definitely be taking a look! Thanks again
When was the book written? It took a while for various third-party libraries to convert to python 3, but the dust has settled pretty well by now. Already there are plenty of things in python 3 that python 2 lacks. And if you expect to be doing anything with non-English text, you should absolutely, definitely switch.
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test = 'Reply from 10.1.1.1: bytes=32 time=39ms TTL=253'
test.split()[4].split('=')[1]

Step by step:

test.split()
['Reply', 'from', '10.1.1.1:', 'bytes=32', 'time=39ms', 'TTL=253']
test.split()[4].split('=')
'time=39ms'
test.split()[4].split('=')
['time', '39ms']
test.split()[4].split('=')[1]
'39ms'

Output:

#1 '39ms'

Another test:

test = 'Reply from 10.1.1.1: bytes=32 time=38833434343434349ms TTL=253'
test.split()[4].split('=')[1]
'38833434343434349ms'
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7 Comments

I don't think this would work, the time value could be something like 2940ms or 374ms so it's not always going to be 5 characters
It will work. .split()[4] gets the 5th element of the list that was created after you split the string. It can be on length n
Ohh, okay, that makes sense, i didn't realize it was splitting the string by spaces and looking at each substring as an element. Thanks!
what about the other lines in the output?
@PadraicCunningham -This is Assuming the OP is using only a single string at a time.
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