Copy packet loss value in terminal into python

[xiaozai]

i have the following code to ping a computer and copy the packet loss value from the ping result

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 import os 
            hostname = "192.168.0.255"
            packetloss = os.system ("ping -c 5 " + hostname+ " | grep -oP '\d+(?=% packet loss')") 
            print (packetloss, 'is packet loss value')  

The result that i get if 100% packet loss is

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100
           (0, 'is packet loss value')

and if there is no packet loss

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0
          (0, 'is packet loss value')

How can i make the above value the same? it always detect 0 on packet loss value.

[rpdom]

os.system just returns the exit code of the command, which will be 0 (success) in this case. You should probably be using subprocess instead of os.system, but you could try os.popen for now

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import os
hostname = "192.168.0.255"
packetloss = os.popen ("ping -c 5 " + hostname+ " | grep -oP '\d+(?=% packet loss)' ").read()
print (packetloss, 'is packet loss value')  

[xiaozai]

change to os.popen. give me errors. "grep: write error: Broken pipe". i try to change to subprocess later

[rpdom]

change to os.popen. give me errors. "grep: write error: Broken pipe". i try to change to subprocess later

Funny, the code I posted above (now I fixed the indentation from your original), works for me

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$ python testprog
('100\n', 'is packet loss value')

[xiaozai]

my bad. there is typing error on my side. thank you for the code. work nicely

[xiaozai]

just notice something. how can i eliminate "\n" from the packet loss value?

[rpdom]

One way is to use rstrip()

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import os
hostname = "192.168.0.255"
packetloss = os.popen ("ping -c 5 " + hostname+ " | grep -oP '\d+(?=% packet loss)' ").read().rstrip()
print (packetloss, 'is packet loss value')

The '\n' is the Linux "newline" character and a simple internet search for "Python remove trailing newline" came up with loads of examples.

[xiaozai]

is there gonna be an error if use this command instead?

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print(packetloss.rstrip(), 'loss value')

[rpdom]

is there gonna be an error if use this command instead?

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print(packetloss.rstrip(), 'loss value')

Try it and find out?

You might even want to try

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print packetloss.rstrip() + ' loss value'

[xiaozai]

already try it. hoping there are no error if i keep using this code. thanks alot

[xiaozai]

Im confuse a little bit. i add another code:

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if packetloss <= 10:
                   print(packetloss, 'is packet loss value')
                   print('this is below 10')
elif packetloss >= 11:
                   print(packetloss, 'is packet loss value')
                   print('this is above 11') 
else:
                   print('invalid number')

However every time i run the code, it always detect above 11 even though the loss value is 0. is there any coding error i have done?

[elParaguayo]

My guess is that you are comparing a string value for packetloss with an integer.

Convert your string to an integer first.

Edit: this should illustrate the problem.

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In [1]: packetloss = "0"

In [2]: packetloss <= 10
Out[2]: False

In [3]: packetloss >= 11
Out[3]: True

In [4]: packetloss = 0

In [5]: packetloss <= 10
Out[5]: True

In [6]: packetloss >= 11
Out[6]: False