Perl

SSH Exec (Execute Command Line)

Demonstrates running a single command on an SSH server with an exec request and retrieving its output. The example connects, authenticates, opens a session channel, sends the command, reads until the server closes the channel, and then checks the exit status.

Background: exec is the workhorse of SSH automation: it runs one command and the server closes the channel when the command exits, which is a definitive end-of-output signal. No PTY is involved, so the shell runs non-interactively — no prompt, no echoed input, no ANSI escape codes — giving clean, parseable output. Remember that an accepted exec request only means the request was accepted; the command's own success is reported through the channel exit status. Command syntax depends on the remote shell, which is the user's default shell on Linux/UNIX and usually CMD.EXE on Windows SSH servers.

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use strict;
use warnings;
use Chilkat2;

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

# Demonstrates running a single command on an SSH server with an exec request and retrieving
# its output.  An exec request runs one command and the server closes the channel when it
# finishes -- no PTY and no shell prompt are involved, so the output is clean and parseable.

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

# The hostname may be a hostname or an IP address.
my $hostname = 'ssh.example.com';
my $port = 22;
my $success = $ssh->Connect($hostname, $port);
if (!$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.  Several session channels may be open at once on one connection.
my $channelNum = $ssh->OpenSessionChannel();
if ($channelNum < 0) {
    print $ssh->LastErrorText, "\n";
    exit;
}

# The command syntax depends on the remote system's shell.  On Linux/UNIX it is typically the
# user's default shell; on Windows SSH servers it is usually CMD.EXE.
#   Linux/UNIX:  "ls -l /tmp"        or  "cd /etc; ls -la"
#   Windows:     "dir"               or  "\"cd \\temp&&dir\""
$success = $ssh->SendReqExec($channelNum, 'ls -l /tmp');
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);

# Read the output until the server sends channel close, which happens when the command exits.
$success = $ssh->ChannelReceiveToClose($channelNum);
if (!$success) {
    print $ssh->LastErrorText, "\n";
    exit;
}

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

print $cmdOutput, "\n";

# An accepted exec request does not mean the command succeeded.  Check the exit status.
if ($ssh->ChannelReceivedExitStatus($channelNum)) {
    print 'Exit status: ', $ssh->GetChannelExitStatus($channelNum), "\n";
}

$ssh->Disconnect();