Lianja

SSH Remote Shell with Multiple Commands

Demonstrates running several commands one after another in a single remote shell session, retrieving each command's output separately. No PTY is requested, so each command is followed by an echoed marker that signals where its output ends.

Background: Interleaving commands and reads in one shell requires a way to know where each command's output stops. An interactive session would use the shell prompt, but without a PTY the shell is non-interactive and never prints one — so the dependable technique is to append echo SOME_MARKER to each command and read up to that marker. Retrieving the text also clears the receive buffer, which matters here: if a marker were left buffered, the next receive would match it immediately and return the wrong output.

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llSuccess = .F.

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

//  Demonstrates running several commands one after another in a single remote shell session,
//  retrieving each command's output separately.
//  
//  No PTY is requested, so the shell runs non-interactively and never prints a command prompt.
//  Because there is no prompt to synchronize on, each command is followed by an "echo" of a
//  unique marker, and the output is read up to that marker.

loSsh = createobject("CkSsh")

lcHostname = "ssh.example.com"
lnPort = 22
llSuccess = loSsh.Connect(lcHostname,lnPort)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

//  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.
lcPassword = "mySshPassword"

llSuccess = loSsh.AuthenticatePw("mySshLogin",lcPassword)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lnChannelNum = loSsh.OpenSessionChannel()
if (lnChannelNum < 0) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

//  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.
llSuccess = loSsh.SendReqShell(lnChannelNum)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

//  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
//  which means no limit -- without it, this call waits forever if the received data never
//  contains a match.
loSsh.ReadTimeoutMs = 15000

llCaseSensitive = .T.

//  ---- 1st command: change directory ----
llSuccess = loSsh.ChannelSendString(lnChannelNum,"cd /tmp; echo END_OF_CMD_1" + Chr(10),"utf-8")
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

llSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"END_OF_CMD_1","utf-8",llCaseSensitive)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

//  Retrieving the text also clears the receive buffer, which matters: if the next marker were
//  left in the buffer, the following receive would match immediately.
lcCmdOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
if (loSsh.LastMethodSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

? lcCmdOutput

//  ---- 2nd command: directory listing ----
llSuccess = loSsh.ChannelSendString(lnChannelNum,"ls; echo END_OF_CMD_2" + Chr(10),"utf-8")
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

llSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"END_OF_CMD_2","utf-8",llCaseSensitive)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lcCmdOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
if (loSsh.LastMethodSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

? lcCmdOutput

//  ---- 3rd command: long listing, then finish the session ----
llSuccess = loSsh.ChannelSendString(lnChannelNum,"ls -l" + Chr(10),"utf-8")
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

//  No more input will be sent.
llSuccess = loSsh.ChannelSendEof(lnChannelNum)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

llSuccess = loSsh.ChannelReceiveToClose(lnChannelNum)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lcCmdOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
if (loSsh.LastMethodSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

? lcCmdOutput

loSsh.Disconnect()


release loSsh