It was a mistake on my side . Semaphores are regulating the write access . I've included the sample code. Thanks for the replies wise ones.
#! /usr/bin/perl -w use strict ; use Socket; use IO::Handle; use IPC::Semaphore ; pipe(PARENTREAD, PARENTWRITE); PARENTWRITE->autoflush(1); my $sem=semget(&IPC_PRIVATE, 1, &IPC_CREAT | 0666) || die "semget: $!\ +n"; warn "semid= $sem\n"; semsign($sem); sub IPC_PRIVATE {0}; sub IPC_RMID {10}; sub IPC_CREAT {0001000}; sub GETVAL {5}; sub semwait { my $sem=shift; semop($sem, pack("s3", 0, -1, 0)) || die "semw: $!\n"; } sub semsign { my $sem=shift; semop($sem, pack("s3", 0, +1, 0)) || die "sems: $!\n"; } sub main () { my $msg ; print "I'm in the parent now \n"; for (my $count = 1 ; $count < 25 ; $count++ ) { my $child_pid = forker(); print "The child process had pid of $child_pid \n"; } my $count = 1 ; open (FH, '>>' , 'test.txt'); while ($msg = <PARENTREAD> ) { if ($msg =~ /PID/) { $count++ ; print "Increasing the count to $count \n"; print FH "$msg"; if($count == 24 ) { last ; } } } } sub forker() { #print " Child is forking \n" ; my $child_pid ; my $panic_monitor_pid ; if(!defined($child_pid = fork())) { print " Forking of child failed \n"; die "Dying abruptly\n"; }elsif($child_pid > 0) { print "In parent \n"; return $child_pid ; }else { #print "In child now \n The child had pid $$" ; $panic_monitor_pid = grandchild(); #print " The grand child has pid of $panic_monitor_pid \n"; exit ; } } sub grandchild () { my $child_pid ; my $panic_monitor_pid ; if(!defined($child_pid = fork())) { print " Forking of child failed \n"; die "Dying abruptly\n"; }elsif($child_pid > 0) { #print "In parent \n"; return $child_pid ; }else { semwait($sem); print PARENTWRITE "In the grandchild \n"; print PARENTWRITE "PID : The child had pid $$\n" ; semsign($sem); #$panic_monitor_pid = panic_monitor(); #print " The grand child has pid of $panic_monitor_pid \n"; exit ; } } main();
In reply to Re^2: Regulating write access to pipes using semaphores
by girishatreya2005
in thread Regulating write access to pipes using semaphores
by girishatreya2005
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