[Tutor] popen()ed file object hangs on close() -- why?

[Doug Stanfield]

I don't know what platform you're on but I'd do something like (untested
code):

class PingPipe(CommandPipe):
     def __init__(self, command=ping, command_options='-c 1',
command_args=host, regexp=ping_re):
         CommandPipe.__init__(self, command, command_options, command_args,
regexp)

Notice the command_options='-c 1'.  This limits you to one ping and if thats
not what you're trying to do, adjust the number.

Apologies in advance for the probable line length mangling of my mailer.

-Doug-
> -----Original Message-----
> From: Evgeny Roubinchtein [mailto:eroubinc@u.washington.edu]
> Sent: Wednesday, July 28, 1999 5:34 PM
> To: tutor@python.org
> Subject: [Tutor] popen()ed file object hangs on close() -- why?
> 
> 
> So, I have written a very simple script to filter the output 
> of a command.  
> Right now it is just the ping command, but I think I can add more. The
> problem is the script hangs.  I realize that the ping command is
> still writing data when I try to close the pipe.  If I knew 
> it's PID, I 
> could try killing it, but I how do I get its PID?  (short of an
> equivalent of 'ps ax | grep ping' ) Here is the script:
> It hangs under both Linux and FreeBSD, in case that matters.
> 
> I know I am doing sthg stupid, I just wish I knew what...
> 
> Any help is greatly appreciated
> 
> ---%<-----
> 
> #! /usr/local/bin/python 
> 
> import re, os, string, sys
> 
> ping = '/bin/ping'
> host = '127.0.0.1'
> ping_re = r'\s+time=(?P<numbers>\d+\.\d*)\s+ms'
> 
> class CommandPipe:
>     def __init__(self, command, command_options, 
> command_args, regexp):
>         self.prog = string.join((command, command_options, 
> command_args), ' ')
>         self.re_obj = re.compile(regexp)
>         self.line = ''
>     def run(self):
>         command_pipe = os.popen(self.prog)
>         maxcount = 5  # this can be adjusted
>         for i in range(maxcount):
>             line = command_pipe.readline()
>             if not line:
>                 break
>             line = string.strip(line)
>             m = self.re_obj.search(line)
>             if m:
>                 for group in m.groups():
>                     print group,
>                 print # a blank line
>         sys.stdout.flush()
>         command_pipe.close()  # the script hangs here
>         return
>         
> 
>                 
> class PingPipe(CommandPipe):
>     def __init__(self, command=ping, command_options='', 
> command_args=host,
>                  regexp=ping_re):
>         CommandPipe.__init__(self, command, command_options, 
> command_args,
>                              regexp)
>         
> def test():
>     p = PingPipe()
>     p.run()
> 
> 
> if __name__=='__main__':
>     test()
>     sys.exit(0)
> 
> 
> 
> --
> Evgeny Roubinchtein, eroubinc@u.washington.edu
> ...................
> SDD: Scratch Disk and Die
> 
> 
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