Remote Tailing Using ssh2_fetch_stream - php

Question

I am trying to do remote tailing using phpseclib. I manged to do this using the following code:
<?php
include('Net/SSH2.php');
include('Crypt/RSA.php');
$server = $_POST['server'];
$ssh = new Net_SSH2($server);
$key = new Crypt_RSA();
$key->loadKey(file_get_contents('/home/{username}/.ssh/id_rsa'));
if (!$ssh->login('{username}', $key)) {
exit('Login Failed');
}
$tail="tail -n 1 {some lof file}";
while ($ssh->isConnected()) {
$ssh->exec(
$tail, function ($str) {
echo $str;
echo "<br>";
flush();
ob_flush();
}
);
}
?>
The problem with the code above is that it logs duplicate entries and I was told that it will not read the log file fast enough if we had to change our log file debug level. It was recommended that I look at ssh2_fetch_stream. I tried this but am honestly very confused. This is my code at the moment:
<?php
include('Net/SSH2.php');
include('Crypt/RSA.php');
$host = $_POST['server'];
$username = "{username}";
$publicKey = "/home/{username}/.ssh/id_rsa.pub";
$privateKey = "/home/{username}/.ssh/id_rsa";
$log = "{some log file}";
$conn = ssh2_connect($host);
if (ssh2_auth_pubkey_file($conn, $username, $publicKey, $privateKey)){
$stream = ssh2_exec($conn, 'tail -n 1 {some log file}');
$stream_out = ssh2_fetch_stream($stream, SSH2_STREAM_STDIO);
if (ob_get_level() == 0)
ob_start();
while ($stream_out) {
$line = fgets($stream_out);
echo $line.'<br />';
ob_flush();
flush();
sleep(1);
}
fclose($stream_out);
ob_end_flush();
}
?>
The above code only prints one line since I am not sure how to do the loop since I can't use "while ($ssh->isConnected())" anymore. I think it is looping but not looping what it is supposed to. Unfortunately because of this I can't test if this would read the log file fast enough.
Any help or pointers will be very much appreciated. I hope this solution will work because I am not allowed to install anything on the remote server who's log file I am supposed to tail.

Answer 1

I was told that it will not read the log file fast enough if we had to
change our log file debug level
Whoever told you that is wrong. phpseclib reads what the SSH server sends, which is exactly what libssh2 (or any SSH client for that matter) does.
The problem with the code above is that it logs duplicate entries
That would make sense. tail -n 1 filename shows you the last entry in the log file. If there's a ten minute gap between entries being made and, in that ten minute, you run that command 100 times then you'll see 100 duplicate entries.
My recommendation: do this (with phpseclib):
$ssh->setTimeout(0);
$tail = 'tail -f /path/to/logfile';
$ssh->exec(
$tail, function ($str) {
echo $str;
echo "<br>";
flush();
ob_flush();
}
);
ie. no while loop, no running the same command a zillion times, etc. Just one command, ran once and into perpetuity.