PowerShell

Set an Environment Variable on an SSH Channel

Demonstrates the Chilkat Ssh.SendReqSetEnv method, which asks the server to set an environment variable for a session channel. The arguments are the channel number, the variable name, and its value. Send these requests before the exec, shell, or subsystem request.

Background: This is the clean way to pass configuration to a remote command without embedding it in the command line. Be aware that many SSH servers restrict which variables clients may set (OpenSSH's AcceptEnv), so a request can be silently ignored or rejected — do not rely on it without verifying the server's policy.

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Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

$success = $false

#  Demonstrates the Ssh.SendReqSetEnv method, which asks the server to set an environment
#  variable for a session channel.  The 1st argument is the channel number, the 2nd is the
#  variable name, and the 3rd is its value.  Send it before the exec, shell, or subsystem
#  request.

$ssh = New-Object Chilkat.Ssh

$sshPort = 22
$success = $ssh.Connect("ssh.example.com",$sshPort)
if ($success -eq $false) {
    $($ssh.LastErrorText)
    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 -eq $false) {
    $($ssh.LastErrorText)
    exit
}

#  Open a session channel.  A negative return value indicates failure.
$channelNum = $ssh.OpenSessionChannel()
if ($channelNum -lt 0) {
    $($ssh.LastErrorText)
    exit
}

#  Set environment variables for the channel.  Multiple variables may be requested.
$success = $ssh.SendReqSetEnv($channelNum,"LANG","en_US.UTF-8")
if ($success -eq $false) {
    $($ssh.LastErrorText)
    exit
}

$success = $ssh.SendReqSetEnv($channelNum,"MY_APP_MODE","production")
if ($success -eq $false) {
    $($ssh.LastErrorText)
    exit
}

#  Now run the command, which sees the requested environment.
$success = $ssh.SendReqExec($channelNum,"echo $MY_APP_MODE")
if ($success -eq $false) {
    $($ssh.LastErrorText)
    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

$success = $ssh.ChannelReceiveToClose($channelNum)
if ($success -eq $false) {
    $($ssh.LastErrorText)
    exit
}

$output = $ssh.GetReceivedText($channelNum,"utf-8")
if ($ssh.LastMethodSuccess -eq $false) {
    $($ssh.LastErrorText)
    exit
}

$($output)

$ssh.Disconnect()