Popen - How can I read data before CTRL+C command is issued

[maffaz]

Cannot be done, you say ? This was done on Ubuntu

Output:
In [23]: ping_proc = subprocess.Popen(['ping', 'google.com'], 
    ...:                              stdout=subprocess.PIPE, stdin=subprocess.PIPE, 
    ...:                              stderr=subprocess.STDOUT, universal_newlines=True)

In [24]: for line_no, line in enumerate(ping_proc.stdout):
    ...:     print(line,)
    ...:     if line_no == 10:
    ...:         print('Killing process')
    ...:         ping_proc.kill()
    ...:         break
    ...:     
64 bytes from lhr25s10-in-f14.1e100.net (216.58.198.174): icmp_seq=3 ttl=50 time=66.0 ms

64 bytes from lhr25s10-in-f14.1e100.net (216.58.198.174): icmp_seq=4 ttl=50 time=66.1 ms

64 bytes from lhr25s10-in-f14.1e100.net (216.58.198.174): icmp_seq=5 ttl=50 time=66.3 ms

64 bytes from lhr25s10-in-f14.1e100.net (216.58.198.174): icmp_seq=6 ttl=50 time=66.0 ms

64 bytes from lhr25s10-in-f14.1e100.net (216.58.198.174): icmp_seq=7 ttl=50 time=66.2 ms

64 bytes from lhr25s10-in-f14.1e100.net (216.58.198.174): icmp_seq=8 ttl=50 time=66.1 ms

64 bytes from lhr25s10-in-f14.1e100.net (216.58.198.174): icmp_seq=9 ttl=50 time=66.1 ms

64 bytes from lhr25s10-in-f14.1e100.net (216.58.198.174): icmp_seq=10 ttl=50 time=66.2 ms

Killing process

I redirect stderr to stdout - some processes use stderr instead of stdout, so suppressing the former is a bad idea

I tried the above code.

With ping it worked as expected and with the tool I am using I got nothing until I pressed CTRL+C again.

any ideas are appreciated as I am pretty much out!!

[volcano63]

With ping it worked as expected and with the tool I am using I got nothing until I pressed CTRL+C again.

any ideas are appreciated as I am pretty much out!!

Maybe, try send_signal with CTRL_C_EVENT. I cannot suggest anything more - very strange behavior of the app.

[maffaz]

With ping it worked as expected and with the tool I am using I got nothing until I pressed CTRL+C again.

any ideas are appreciated as I am pretty much out!!

Maybe, try send_signal with CTRL_C_EVENT. I cannot suggest anything more - very strange behavior of the app.

When I say CTRL+C i meant kill(self.proc.pid, signal.CTRL_C_EVENT) :).

Yes I have tried everything.. I am programming it into a PyQt App and I have also gone through all of their Qprocess commands as well.

It is nice to have a second opinion so thank you very much.

I think I will have to go to the C developer and ask him to recode it to send it via STDOUT or ERR or anywhere!!

I will hopefully have an answer once I can catch him and I will post here to satisfy anyone's curiosities!

[maffaz]

for anyone that is interested. I have found the problem but it is not Python Related, Rather the C implementation of the tool..

The problem here is probably, that the output of your CLI program is block buffered, since the output file descriptor is not associated with a terminal. You claim, that it works with "ping" instead of your cli program, so it definitively has to be an issue with the subprocess itself.

Since you programmed the cli program yourself, make sure that it does not buffer the output (i.e. put an fflush() after each line which is printed.

You can read the discussion here..

https://stackoverflow.com/questions/5103...1#51078297