Objective-C

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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Objective-C

#import <CkoSFtp.h>
#import <NSString.h>

BOOL success = NO;

//  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.

CkoSFtp *sftp = [[CkoSFtp alloc] init];

//  Connect, authenticate, and initialize the SFTP subsystem.
int port = 22;
success = [sftp Connect: @"sftp.example.com" port: [NSNumber numberWithInt: port]];
if (success == NO) {
    NSLog(@"%@",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.
NSString *password = @"mySshPassword";

success = [sftp AuthenticatePw: @"mySshLogin" password: password];
if (success == NO) {
    NSLog(@"%@",sftp.LastErrorText);
    return;
}

success = [sftp InitializeSftp];
if (success == NO) {
    NSLog(@"%@",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" newPath: @"subdir/data_backup.bin"];
if (success == NO) {
    NSLog(@"%@",sftp.LastErrorText);
    return;
}

NSLog(@"%@",@"Hard link created.");

[sftp Disconnect];