lchown()

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.

group

The group ID of the new owner.

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.

Only processes with an effective user ID equal to the user ID of the file or with appropriate privileges (for example, the superuser) may change the ownership of a file.

In QNX Neutrino, the _POSIX_CHOWN_RESTRICTED flag is enforced. This means that only the superuser may change the ownership of a file. The group of a file may be changed by the superuser, or also by a process with the effective user ID equal to the user ID of the file, if (and only if) owner is equal to the user ID of the file and group is equal to the effective group ID of the calling process.

If the path argument refers to a regular file, the set-user-ID (S_ISUID) and set-group-ID (S_ISGID) bits of the file mode are cleared, if the function is successful.

If lchown() succeeds, the st_ctime field of the file is marked for update.

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 arguments points to an empty string.

ENOSYS

The lchown() function isn't implemented for the filesystem specified in path.

ENOTDIR

A component of the path prefix isn't a directory.

EPERM

The effective user ID does not match the owner of the file, or the calling process does not 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 XSI

See also:

chmod(), chown(), errno, fchown(), fstat(), open(), stat()