perlquestion
x12345
<p>
Hello, the experts:
<br>
According to someone's code, I try to reproduce the
following: open a filehandle to run a command in remote linux machine, set it to non-blocking filehand, then use a sysread loop to read the results from the filehandle. It does't work. Could you help me check what is wrong in my code :</p>
<code>
my $cmd = '/opt/rssh/bin/ssh';
my $machine = "remote_machine";
open(my $fh, "-|", "$cmd $machine \"hostname;uptime\" 2>&1") or die "cannot open fh";
my $flags = fcntl($fh, F_GETFL, 0) or die "\ncan't get flags for the pipe: $!\n";
fcntl($fh, F_SETFL, $flags | O_NONBLOCK) or die "\ncan't set flags: $!\n";
my $out = $fh;
my $bytes_read = -1;
my $blocksize = 1024;
my $result = "";
while ($bytes_read) {
my $buf;
$bytes_read = sysread($out, $buf, $blocksize);
if (defined($bytes_read)) {
if ($bytes_read == 0) {
close($out);
last;
} else {
print "\nbuf content\n";
$result.= $buf;
}
}else {
if ($! == EAGAIN()) {
print "\nEAGAIN is set\n";
last;
} else {
last;
}
}
}
print "\nresult is: $result \n";
</code>
The result is:
<code>
EAGAIN is set
result is:
</code>
But if I replace the "while ($bytes_read) " with the while (<$fl>) as the following, I can get the result.
<br>
<code>
my $cmd = '/opt/rssh/bin/ssh';
my $machine = "remote_machine";
open(my $fh, "-|", "$cmd $machine \"hostname;uptime\" 2>&1") or die "cannot open fh";
#my $flags = fcntl($fh, F_GETFL, 0) or die "\ncan't get flags for the pipe: $!\n";
#fcntl($fh, F_SETFL, $flags | O_NONBLOCK) or die "\ncan't set flags: $!\n";
my @result ;
while (<$fh>) {
# chomp;
push @result,$_;
}
print "\nresult is: @result \n";
</code>
<br>The result is
<code>
result is: ccwsge0553
13:40:10 up 4 days, 2 min, 0 users, load average: 0.08, 0.03, 0.01
</code>
What is wrong in my code with non-blocking/sysread? Thanks in advance!