Dart

Check if a Remote File or Directory Exists

Demonstrates the Chilkat SFtp.FileExists method, which checks a remote path and returns an integer describing what is there. The first argument is the remote path and the second (followLinks) selects whether a symbolic link is followed to its target. The return value is -1 on error, 0 if nothing exists, 1 for a file, 2 for a directory, 3 for a symbolic link, and higher values for special entry types.

Background: This returns more than a yes/no because "does it exist" usually comes with "and is it the kind of thing I expect" — a job that means to write a file should notice if a directory already occupies the path. The followLinks flag decides whether a symbolic link is reported as a link (3, only when not following) or transparently resolved to its target's type. Always handle the -1 case: it means the check itself failed, which is different from the path not existing.

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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // Demonstrates the SFtp.FileExists method, which checks a remote path and returns an integer
  // describing what is there.  The 1st argument is the remote path and the 2nd (followLinks)
  // selects whether a symbolic link is followed to its target.

  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;
  }

  // When followLinks is true, a symbolic link is followed and the target's type is returned.
  final followLinks = true;
  final result = sftp.fileExists('subdir/report.pdf', followLinks);

  // Interpret the return value.
  if (result == -1) {
    print(sftp.lastErrorText);
    return;
  }

  if (result == 0) {
    print('The path does not exist.');
  }

  if (result == 1) {
    print('A regular file exists.');
  }

  if (result == 2) {
    print('A directory exists.');
  }

  // Other possible values: 3 = symbolic link (only when followLinks is false), 4 = special
  // entry, 5 = unknown, 6 = socket, 7 = character device, 8 = block device, 9 = FIFO.

  sftp.disconnect();
}