[Canberra-pm] How to exit a hung pipe to a shell command [SEC=UNCLASSIFIED]

[John.Hockaday at ga.gov.au]

Hi All,

I have a PERL pipe that calls a c++ binary called
"/public/data/asddgate/isite/current/bin/zping".  It tries to ping an
external zserver using the hostname and port parameters.  If the ping works
it returns something like:

Z39.50 server at www.ga.gov.au on port 6668 is alive.

 and then exits the pipe.

Sometimes it can't zping because the zserver is down or the zping command is
not allowed through a firewall so the pipe hangs for 224 seconds.  

There is an option of -t NN which sets how long to wait for a response from
the zserver and I set this to 60 seconds (zping -t 60) but this doesn't seem
to work when the pipe hangs.

I have tried to overcome this by using a combination of PERL while and sleep
but I just can't seem to get it to work.  Here is a snippet of my code:

#################################################################
#!/opt/csw/bin/perl
###################
# sleep for 60 seconds or zping
###################
  $hostname = shift;
  $port = shift;

  $zping_cmd = '/public/data/asddgate/isite/current/bin/zping';
  my ($alive);

  open (ZPING, "$zping_cmd -t 60 $hostname $port 2>&1 |")
    or die "Cannot open zping: $!";
  while (($results = <ZPING>) || (sleep(60) != 60) ) {
    print "$results\n";
    if ($results =~ m/is alive/) {
      $alive = 1;
      print "$results\n";
      last;
    }
  }
  print "closing ZPING and alive = $alive\n";
  close ZPING;
#################################################################

Am I doing this correctly or is there some other way to break this pipe after
waiting for a set time and still continue with the code?  I tried alarm but
it exits the script and I want to keep on processing.

Thanks.


 John Hockaday
 Geoscience Australia
 GPO Box 378
 Canberra ACT 2601
 (02) 6249 9735
 http://www.ga.gov.au/ 
 john.hockaday\@ga.gov.au