向perl脚本发送HUP信号只有第一次成功 - Chinaunix

use strict;
use IO::File;
use POSIX;
my $pid_file='/home/perl.pid';
my $quit=0;
$SIG{TERM} = $SIG{INT} =\&do_term;
$SIG{HUP} = \&DoHup;
if (-e $pid_file) {
open PIDFILE,"<$pid_file" or die "$!\n";
my $pid=<PIDFILE>;
close PIDFILE;
die "Server already running with pid $pid" if kill 0 => $pid;
warn "Removing old PID file for $0";
die "Can't unlink PID file $pid_file" unless (-w $pid_file && unlink $pid_file);
}
open NEWPID,">$pid_file" or die "Can't create pid file:$!";
my $pid= daemon();
print NEWPID "$pid\n";
close NEWPID;
open LOGA," >>/home/test.log ";
syswrite LOGA,"$quit\n";
my $count;
while (!$quit) {
$count++;
syswrite LOGA,"hello a $count\n";
sleep 1;
}
sub daemon{
die "can't fork!" unless defined (my $child = fork);
exit 0 if $child;
setsid();
print "Server start with pid $\n";
open(STDIN,"</dev/null");
open(STDOUT,">/dev/null");
open(STDERR,">&STDOUT");
chdir '/';
umask(0);
$ENV{PATH} = '/bin:/sbin/:/usr/bin:/usr/sbin';
return $;
}
sub do_term{
unlink $pid_file;
$quit++;
}
sub DoHup{
warn "received SIGHUP,prepare to reload...\n";
unlink $pid_file;
exec '/usr/bin/perl','/home/daemon.pl';
}

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Signals are tricky beasts. When you exec to restart your program, the reborn version inherits a set of blocked signals from its parent. Inside a signal handler, that signal is blocked. So if your signal handler simply called exec right away, the new process would have SIGHUP blocked. You could only restart your program once!

my $signals = POSIX::SigSet->new(SIGHUP,SIGTERM,SIGINT);
sigprocmask(SIG_UNBLOCK,$signals);

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use POSIX qw(:signal_h sigprocmask);
my $SELF = "/path/to/my/program";
my @ARGS = @ARGV; # save for later
$SIG{HUP} = \&phoenix;
# your program
sub phoenix {
# make signals harmless
for my $nal (qw[ALRM CHLD HUP INT PIPE TERM]) {
$SIG{$nal} = sub { };
}
# reenable them
my $s = POSIX::SigSet->new;
my $t = POSIX::SigSet->new;
sigprocmask(SIG_BLOCK, $s, $t);
# and restart
print "Restarting\n";
exec $SELF => @ARGS;
die "Couldn't exec $SELF => @ARGS\n";
}

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