lchown()

Updated: October 26, 2022

Change the user ID and group ID of a file or symbolic link

Synopsis:

#include <sys/types.h>
#include <unistd.h>

int lchown( const char * path, 
           uid_t owner, 
           gid_t group );

Arguments:

path
The name of the file whose ownership you want to change.
owner
The user ID of the new owner, or -1 if you don't want to change the owner.
group
The group ID of the new owner, or -1 if you don't want to change the group.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The lchown() function changes the user ID and group ID of the file specified by path to be the numeric values contained in owner and group, respectively. It's similar to chown(), except in the case where the named file is a symbolic link. In this case, lchown() changes the ownership of the symbolic link file itself, while chown() changes the ownership of the file or directory to which the symbolic link refers.

Returns:

0
Success.
-1
An error occurred (errno is set).

Errors:

EACCES
Search permission is denied on a component of the path prefix.
ELOOP
Too many levels of symbolic links or prefixes.
ENAMETOOLONG
The length of the path string exceeds PATH_MAX, or a pathname component is longer than NAME_MAX.
ENOENT
A component of the path prefix doesn't exist, or the path argument points to an empty string.
ENOSYS
The lchown() function isn't implemented for the filesystem underlying the path specified in path.
ENOTDIR
A component of the path prefix isn't a directory.
EPERM
The effective user ID doesn't match the owner of the file, or the calling process doesn't have appropriate privileges.
EROFS
The named file resides on a read-only filesystem.

Examples:

/*
 * Change the ownership of a list of files
 * to the current user/group
 */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>

int main( int argc, char **argv )
  {
    int i;
    int ecode = 0;

    for( i = 1; i < argc; i++ ) {
      if( lchown( argv[i], getuid(), getgid() ) == -1 ) {
        perror( argv[i] );
        ecode++;
      }
    }
    return( ecode );
  }

Classification:

POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes