Java

Create a Hard Link on an SFTP Server

Demonstrates the Chilkat SFtp.HardLink method, which creates a hard link to an existing remote file. The first argument is the existing file and the second is the new link path. It uses the OpenSSH hardlink@openssh.com extension and succeeds only when the server supports it.

Background: A hard link is a second name for the same file data, not a pointer to a path: both names are equal, the data persists until the last name is removed, and there is no "original" to break. Unlike a symbolic link it cannot span filesystems and cannot target a directory. Because it depends on a non-standard OpenSSH extension, expect it to fail against servers that do not implement it.

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Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    //  Demonstrates the SFtp.HardLink method, which creates a hard link to an existing remote file.
    //  The 1st argument is the existing file and the 2nd is the new link path.

    CkSFtp sftp = new CkSFtp();

    //  Connect, authenticate, and initialize the SFTP subsystem.
    int port = 22;
    success = sftp.Connect("sftp.example.com",port);
    if (success == false) {
        System.out.println(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.
    String password = "mySshPassword";

    success = sftp.AuthenticatePw("mySshLogin",password);
    if (success == false) {
        System.out.println(sftp.lastErrorText());
        return;
        }

    success = sftp.InitializeSftp();
    if (success == false) {
        System.out.println(sftp.lastErrorText());
        return;
        }

    //  Create a hard link.  This uses the OpenSSH hardlink@openssh.com extension and succeeds only
    //  when the server supports it.
    success = sftp.HardLink("subdir/data.bin","subdir/data_backup.bin");
    if (success == false) {
        System.out.println(sftp.lastErrorText());
        return;
        }

    System.out.println("Hard link created.");

    sftp.Disconnect();
  }
}