Perl (SSH to remote host, Issues the command and close the session without waiting it to finish…)

Question

Script goes to the remote server and runs a shell script "snap.sh" using Net::SSH::Perl. This shell script takes almost 10mins to end, and my perl program waits until it gets output. I want to run the shell script on the remote sever and the program should close the SSH session without waiting for the script to finishes on the remote server.

my $ssh = Net::SSH::Perl->new($host, protocol =>2);
$ssh->login($username, $password);
my $cmd="./bin/snap.sh";
my($stdout, $stderr, $exit) = $ssh->cmd($cmd);

Answer 1

Lookup the nohup command. Here is quick post to get you started . For completeness here is what should work in your case...

my $cmd="nohup ./bin/snap.sh &";

Answer 2

Untested, but can't you just do what ssh -f does?

my $ssh = Net::SSH::Perl->new($host, protocol =>2);
$ssh->login($username, $password);
defined (my $pid = fork) or die "fork: $!";
if ($pid) {
    close $ssh->sock;
    undef $ssh;
} else {
    my $cmd="./bin/snap.sh";
    my($stdout, $stderr, $exit) = $ssh->cmd($cmd);
    POSIX::_exit($exit);
}

Answer 3

To run a background job on a remote host, you also need to dissociate from any controlling ttys on the local machine. Try a command like:

my $cmd = "./bin/snap.sh < /dev/null > /dev/null 2>&1 &";

I think using nohup is optional.

Answer 4

I use Net::OpenSSH for this. It has a spawn method that does exactly what you're looking for.

  my %conn = map { $_ => Net::OpenSSH->new($_) } @hosts;
  my @pid;
  for my $host (@hosts) {
      open my($fh), '>', "/tmp/out-$host.txt"
        or die "unable to create file: $!";
      push @pid, $conn{$host}->spawn({stdout_fh => $fh}, $cmd);
  }

  waitpid($_, 0) for @pid;