Perl

Release an SSH Channel's Local Resources

Demonstrates the Chilkat Ssh.ChannelRelease method, which releases Chilkat's retained local resources for a channel after all output and exit information has been retrieved. The only argument is the channel number.

Background: Chilkat retains a channel's buffered output and exit information after the channel closes, so you can still read a command's final output. That retention costs memory, and a long-running program that opens many channels should release each one when finished with it. Note this is not a channel-closing method — it sends neither EOF nor CLOSE. Retrieve everything you need first, because releasing discards it.

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use strict;
use warnings;
use Chilkat2;

# Demonstrates the Ssh.ChannelRelease method, which releases Chilkat's retained local resources
# for a channel after all output and exit information has been retrieved.  The only argument is
# the channel number.

my $ssh = Chilkat2::Ssh->new;

my $sshPort = 22;
my $success = $ssh->Connect('ssh.example.com', $sshPort);
if (!$success) {
    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.
my $password = 'mySshPassword';

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

# Open a session channel.  A negative return value indicates failure.
my $channelNum = $ssh->OpenSessionChannel();
if ($channelNum < 0) {
    print $ssh->LastErrorText, "\n";
    exit;
}

$success = $ssh->SendReqExec($channelNum, 'uname -a');
if (!$success) {
    print $ssh->LastErrorText, "\n";
    exit;
}

# IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
# it, this call waits forever if the server never sends channel close.
$ssh->ReadTimeoutMs(15000);

# Retrieve everything of interest before releasing the channel.
$success = $ssh->ChannelReceiveToClose($channelNum);
if (!$success) {
    print $ssh->LastErrorText, "\n";
    exit;
}

my $output = $ssh->GetReceivedText($channelNum, 'utf-8');
if (!$ssh->LastMethodSuccess) {
    print $ssh->LastErrorText, "\n";
    exit;
}

print $output, "\n";

# Release the retained local resources.  This does not send EOF or CLOSE.
$ssh->ChannelRelease($channelNum);

$ssh->Disconnect();