Setting up a Daemon

• The FAM daemon cannot actually execute a command.
• Frequently want to set up a daemon process to do the monitoring:

#!/usr/bin/perl -w
use strict;
use SGI::FAM;
my $monitor_file = '/some/interesting/file';
my $pid_file = '/var/run/some.pid';
my $pid = fork();
if ($pid) {
    # new pid number to log
    open(PID_LOG, "> $pid_file") || die "open($pid_file): $!";
    print PID_LOG "$pid\n";
    close(PID_LOG);
    print "Started with pid = $pid \n";
    exit(1);
}
else {
    # In the child process
    $pid = $$;
    # open log file and pipe stdout and stderr to it
    open(LOG, "| /usr/bin/logger -t $proc_name") || exit ;
    select(LOG);
    $| = 1;
    select(STDOUT);
    print LOG "\n", '=' x 78, "\nStarting $proc_name at: " .
              localtime(), "  Process ID: $pid\n\n";
    close(STDOUT);
    open(STDOUT, ">&LOG") || exit;
    close(STDERR);
    open(STDERR, ">&LOG") || exit;
    my $fam = new SGI::FAM;
    $fam->monitor($monitor_file);
    while (1) {
        my $event = $fam->next_event;  # blocks here
        print "Heh! $monitor_file has changed\n";
    }
}