Read an SSH Channel with a Byte Threshold

See more SSH Examples

Demonstrates the Chilkat Ssh.ChannelReadAndPoll2 method, which works like ChannelReadAndPoll but also returns once newly processed data brings the total buffered data to or above a byte threshold. The arguments are the channel number, the poll timeout, and the threshold.

The integer return value is -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or channel close was processed, or — when greater than 0 — the total bytes currently buffered for the channel (not the bytes newly received by this call).

<?php

include("chilkat.php");

$success = false;

//  Demonstrates the Ssh.ChannelReadAndPoll2 method, which works like ChannelReadAndPoll but also
//  returns once the total buffered data reaches or exceeds a byte threshold.  The 1st argument is
//  the channel number, the 2nd is the poll timeout, and the 3rd is the byte threshold.

$ssh = new CkSsh();

$sshPort = 22;
$success = $ssh->Connect('ssh.example.com',$sshPort);
if ($success == false) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
$password = 'mySshPassword';

$success = $ssh->AuthenticatePw('mySshLogin',$password);
if ($success == false) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

$channelNum = $ssh->OpenSessionChannel();
if ($channelNum < 0) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

//  Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
//  raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
//  echo typed commands back, and skips interactive login scripts.  The output is therefore
//  clean and easily parseable -- but because no prompt is ever sent, code must not wait for
//  one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
$success = $ssh->SendReqShell($channelNum);
if ($success == false) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

$success = $ssh->ChannelSendString($channelNum,'cat /var/log/syslog\n','utf-8');
if ($success == false) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

//  Return when output goes quiet for 500ms, or once about 64KB has been buffered.  The
//  threshold is not a hard buffer limit -- a whole SSH packet may push the total above it.
$pollTimeoutMs = 500;
$maxNumBytes = 65536;
//  The return value is: -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or
//  channel close was processed, or the total number of buffered bytes when greater than 0.
$result = $ssh->ChannelReadAndPoll2($channelNum,$pollTimeoutMs,$maxNumBytes);
if ($result == -1) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

if ($result == -2) {
    print 'No channel data arrived before the timeout.' . "\n";
}

if ($result == 0) {
    print 'EOF or channel close was processed.  Buffered data may still remain.' . "\n";
}

if ($result > 0) {
    print 'Total bytes buffered: ' . $result . "\n";
}

$output = $ssh->getReceivedText($channelNum,'utf-8');
if ($ssh->get_LastMethodSuccess() == false) {
    print $ssh->lastErrorText() . "\n";
    exit;
}

print $output . "\n";

$ssh->Disconnect();

?>