Dart

Read Text from a Remote SFTP File (Sequential)

Demonstrates the Chilkat SFtp.ReadFileText method, which reads up to a number of bytes from the current position of an open handle and decodes them to text. The arguments are the handle, the maximum number of bytes, and the charset. This example reads in chunks until end-of-file.

Background: Reading a file in bounded chunks keeps memory use predictable regardless of file size, which is why the loop reads a fixed amount and repeats until Eof. A subtlety worth knowing: the byte limit is applied to the encoded bytes, so a chunk boundary could in principle fall in the middle of a multibyte character — accumulating the pieces and decoding the whole avoids any such issue in practice here since the text is reassembled in a StringBuilder.

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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // Demonstrates the SFtp.ReadFileText method, which reads up to a number of bytes from the current
  // position of an open handle and decodes them to text.  The 1st argument is the handle, the 2nd
  // is the maximum number of bytes, and the 3rd is the charset.

  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;
  }

  // Open the remote file for reading.
  final String handle;
  try {
    handle = sftp.openFile('subdir/notes.txt', 'readOnly', 'openExisting');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Read the file in chunks until end-of-file, accumulating the text.
  final sbContent = CkStringBuilder();
  final chunkSize = 4096;
  var reading = true;
  while (reading) {
    final chunk = sftp.readFileText(handle, chunkSize, 'utf-8');
    if (sftp.lastReadFailed(handle)) {
      print(sftp.lastErrorText);
      return;
    }

    sbContent.append(chunk);

    // Stop once the end of the file has been reached.
    reading = !sftp.eof(handle);
  }

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

  print(sbContent.getAsString());

  sftp.disconnect();
}