LinuxQuestions.org - [SOLVED] Piping twice the ping command

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Piping twice the ping command

I am trying to pipe the output from ping twice but I do not get any output in the end.

For example if I pipe ping once as such below there is no problem.

>ping 127.0.0.1 | grep ttl
64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=0.060 ms
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.065 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.052 ms
64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=0.067 ms

Now trouble starts when I try to pipe this output once more like this:

>ping 127.0.0.1 | grep ttl | awk '{print $7}'

This does not return anything.

Does anyone have an explanation? Is it something to do with eof of stdout?

How can I work this around to get the expected result? I am basically trying to extract the time value to stdout.

Are you sure, because it works for me:

Code:

bash-3.1$ ping -c 5 127.0.0.1 | grep ttl | awk '{ print $7 }'

time=0.036

time=0.036

time=0.036

time=0.041

time=0.035

The output is buffered and the pipe does not return anything until the buffer is flushed or the command is terminated, as in H_TeXMeX_H's example. You can try:

Code:

ping 127.0.0.1 | grep --line-buffered ttl | awk '{print $7}'

It works for me as well once the "-c 5" added.

However I want to avoid this option since in this case I am only getting the result once the 5 pings are done.

I need to see the result as it is pinging. A sort of real time monitoring.

Edit. That's the --line-buffered option that I needed. Cheers