Node.js

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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function chilkatExample() {

    var success = false;

    //  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.

    var sftp = new chilkat.SFtp();

    //  Connect, authenticate, and initialize the SFTP subsystem.
    var port = 22;
    success = sftp.Connect("sftp.example.com",port);
    if (success == false) {
        console.log(sftp.LastErrorText);
        return;
    }

    //  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.
    var password = "mySshPassword";

    success = sftp.AuthenticatePw("mySshLogin",password);
    if (success == false) {
        console.log(sftp.LastErrorText);
        return;
    }

    success = sftp.InitializeSftp();
    if (success == false) {
        console.log(sftp.LastErrorText);
        return;
    }

    var handle = sftp.OpenFile("subdir/data.txt","readOnly","openExisting");
    if (sftp.LastMethodSuccess == false) {
        console.log(sftp.LastErrorText);
        return;
    }

    var reading = true;
    var chunkSize = 4096;
    var bd = new chilkat.BinData();
    while (reading) {
        success = sftp.ReadFileBd(handle,chunkSize,bd);

        //  Distinguish an actual read failure from a normal EOF.  On EOF the read succeeds, returns
        //  zero bytes, and LastReadFailed is false.
        if (sftp.LastReadFailed(handle)) {
            console.log("Read failed: " + sftp.LastErrorText);
            return;
        }

        reading = !sftp.Eof(handle);
    }

    success = sftp.CloseHandle(handle);
    if (success == false) {
        console.log(sftp.LastErrorText);
        return;
    }

    console.log("Read " + bd.NumBytes + " bytes with no read failures.");

    sftp.Disconnect();

}

chilkatExample();