Dart

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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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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.

  final sftp = CkSFtp();

  // Connect, authenticate, and initialize the SFTP subsystem.
  final port = 22;
  try {
    sftp.connect('sftp.example.com', port);
  } on ChilkatException catch (e) {
    print(e.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.
  final password = 'mySshPassword';

  try {
    sftp.authenticatePw('mySshLogin', password);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    sftp.initializeSftp();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final String handle;
  try {
    handle = sftp.openFile('subdir/data.txt', 'readOnly', 'openExisting');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  var reading = true;
  final chunkSize = 4096;
  final bd = CkBinData();
  while (reading) {
    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)) {
      print('Read failed: ${sftp.lastErrorText}');
      return;
    }

    reading = !sftp.eof(handle);
  }

  try {
    sftp.closeHandle(handle);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Read ${bd.numBytes} bytes with no read failures.');

  sftp.disconnect();
}