Re^3: use sysread to read non-blocking filehandle

[x12345]

If I just use once sysread to try, it is still empty. Here is the code, what is wrong in the code?

my $cmd = '/opt/rssh/bin/ssh';
my $machine = "remote_machine";

open(my $fh, "-|", "$cmd $machine \"hostname;sleep 5;uptime\" 2>&1") o
+r die "cannot open fh";

my $flags = fcntl($fh, F_GETFL, 0) or die "\ncan't get flags for the p
+ipe: $!\n";
fcntl($fh, F_SETFL, $flags | O_NONBLOCK) or die "\ncan't set flags: $!
+\n";

my $out = $fh;
my $bytes_read = -1;
my $blocksize = 1024;
my $result = "";
my $buf;

$bytes_read = sysread($out, $buf, $blocksize);

print "\nl buf content is:\n $buf \n";
close $out;

[Corion]

Maybe you want to learn what "nonblocking" really means?

In short, "nonblocking" means that the sysread call will return immediately and tell you how many bytes were read at this time. If your filehandle has nothing to read, it will not block. Blocking means "wait until data is avilable".