Visual FoxPro

Check Whether the Last SFTP Read Failed

Demonstrates the Chilkat SFtp.LastReadFailed method, which returns whether the most recent read for a handle failed. The only argument is the handle. A normal end-of-file is not a failure.

Background: A chunked read loop needs to tell three outcomes apart: more data, a clean end-of-file, and an actual error such as a dropped connection or a revoked handle. LastReadFailed isolates the error case — it is false on a normal EOF read (which succeeds with zero bytes) and true for an empty, malformed, or already-closed handle — so the loop can stop cleanly on EOF but bail out with an error message on a genuine failure.

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LOCAL lnSuccess
LOCAL loSftp
LOCAL lnPort
LOCAL lcPassword
LOCAL lcHandle
LOCAL lnReading
LOCAL lnChunkSize
LOCAL loBd

lnSuccess = 0

*  Demonstrates the SFtp.LastReadFailed method, which returns whether the most recent read for a
*  handle failed.  The only argument is the handle.  A normal end-of-file is NOT a failure.

loSftp = CreateObject('Chilkat.SFtp')

*  Connect, authenticate, and initialize the SFTP subsystem.
lnPort = 22
lnSuccess = loSftp.Connect("sftp.example.com",lnPort)
IF (lnSuccess = 0) THEN
    ? loSftp.LastErrorText
    RELEASE loSftp
    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 = loSftp.AuthenticatePw("mySshLogin",lcPassword)
IF (lnSuccess = 0) THEN
    ? loSftp.LastErrorText
    RELEASE loSftp
    CANCEL
ENDIF

lnSuccess = loSftp.InitializeSftp()
IF (lnSuccess = 0) THEN
    ? loSftp.LastErrorText
    RELEASE loSftp
    CANCEL
ENDIF

lcHandle = loSftp.OpenFile("subdir/data.txt","readOnly","openExisting")
IF (loSftp.LastMethodSuccess = 0) THEN
    ? loSftp.LastErrorText
    RELEASE loSftp
    CANCEL
ENDIF

lnReading = 1
lnChunkSize = 4096
loBd = CreateObject('Chilkat.BinData')
DO WHILE lnReading
    lnSuccess = loSftp.ReadFileBd(lcHandle,lnChunkSize,loBd)

    *  Distinguish an actual read failure from a normal EOF.  On EOF the read succeeds, returns
    *  zero bytes, and LastReadFailed is 0.
    IF (loSftp.LastReadFailed(lcHandle)) THEN
        ? "Read failed: " + loSftp.LastErrorText
        RELEASE loSftp
        RELEASE loBd
        CANCEL
    ENDIF

    lnReading = NOT loSftp.Eof(lcHandle)
ENDDO

lnSuccess = loSftp.CloseHandle(lcHandle)
IF (lnSuccess = 0) THEN
    ? loSftp.LastErrorText
    RELEASE loSftp
    RELEASE loBd
    CANCEL
ENDIF

? "Read " + STR(loBd.NumBytes) + " bytes with no read failures."

loSftp.Disconnect()

RELEASE loSftp
RELEASE loBd