Visual FoxPro

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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LOCAL lnSuccess
LOCAL loSsh
LOCAL lcHostname
LOCAL lnPort
LOCAL lcPassword
LOCAL lnChannelNum
LOCAL lnCaseSensitive
LOCAL lcCmdOutput

lnSuccess = 0

*  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('Chilkat.Ssh')

lcHostname = "ssh.example.com"
lnPort = 22
lnSuccess = loSsh.Connect(lcHostname,lnPort)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
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"

lnSuccess = loSsh.AuthenticatePw("mySshLogin",lcPassword)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lnChannelNum = loSsh.OpenSessionChannel()
IF (lnChannelNum < 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
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.
lnSuccess = loSsh.SendReqShell(lnChannelNum)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
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

lnCaseSensitive = 1

*  ---- 1st command: change directory ----
lnSuccess = loSsh.ChannelSendString(lnChannelNum,"cd /tmp; echo END_OF_CMD_1" + CHR(10),"utf-8")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"END_OF_CMD_1","utf-8",lnCaseSensitive)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
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 = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

? lcCmdOutput

*  ---- 2nd command: directory listing ----
lnSuccess = loSsh.ChannelSendString(lnChannelNum,"ls; echo END_OF_CMD_2" + CHR(10),"utf-8")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"END_OF_CMD_2","utf-8",lnCaseSensitive)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lcCmdOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
IF (loSsh.LastMethodSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

? lcCmdOutput

*  ---- 3rd command: long listing, then finish the session ----
lnSuccess = loSsh.ChannelSendString(lnChannelNum,"ls -l" + CHR(10),"utf-8")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

*  No more input will be sent.
lnSuccess = loSsh.ChannelSendEof(lnChannelNum)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lnSuccess = loSsh.ChannelReceiveToClose(lnChannelNum)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lcCmdOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
IF (loSsh.LastMethodSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

? lcCmdOutput

loSsh.Disconnect()

RELEASE loSsh