Tcl

Get the Exit Status of a Remote SSH Command

Demonstrates the Chilkat Ssh.GetChannelExitStatus method, which returns the remote process exit status for a channel. The only argument is the channel number. Call it only after ChannelReceivedExitStatus returns true.

Background: The exit status is how you learn whether a remote command actually succeeded — recall that a successful exec request only means the request was accepted. By Unix convention 0 means success and any nonzero value indicates a failure. Retrieve it promptly after the receive operation and before calling unrelated SSH methods or releasing the channel, since the completed channel record can be discarded.

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Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the Ssh.GetChannelExitStatus method, which returns the remote process exit
#  status for a channel.  The only argument is the channel number.  Call it only after
#  ChannelReceivedExitStatus returns 1.

set ssh [new_CkSsh]

set sshPort 22
set success [CkSsh_Connect $ssh "ssh.example.com" $sshPort]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    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.
set password "mySshPassword"

set success [CkSsh_AuthenticatePw $ssh "mySshLogin" $password]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

set channelNum [CkSsh_OpenSessionChannel $ssh]
if {$channelNum < 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

set success [CkSsh_SendReqExec $ssh $channelNum "grep -q root /etc/passwd"]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    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.
CkSsh_put_ReadTimeoutMs $ssh 15000

set success [CkSsh_ChannelReceiveToClose $ssh $channelNum]
if {$success == 0} then {
    puts [CkSsh_lastErrorText $ssh]
    delete_CkSsh $ssh
    exit
}

#  Retrieve the exit status immediately, before calling unrelated SSH methods or releasing the
#  channel, because the completed channel record can be discarded.
if {CkSsh_ChannelReceivedExitStatus $ssh $channelNum} then {
    set exitStatus [CkSsh_GetChannelExitStatus $ssh $channelNum]
    puts "Exit status: $exitStatus"

    #  By convention, 0 means the remote command succeeded.
    if {$exitStatus == 0} then {
        puts "The remote command succeeded."
    }     else {
        puts "The remote command reported a failure."
    }

}

CkSsh_Disconnect $ssh

delete_CkSsh $ssh