fchown()

change the user ID and group ID of a file

Synopsis:

#include <sys/types.h>
#include <unistd.h>
int fchown( int fd, uid_t owner, gid_t group );

Description:

The fchown() function changes the user ID and group ID of the file referenced by fd to be the numeric values contained in owner and group, respectively.

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

In QNX4.1 or later, the _POSIX_CHOWN_RESTRICTED flag is enforced. This means that only the super user may change the ownership of a file. The group of a file may be changed by the super user, 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 fd 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 fchown() succeeds, the st_ctime field of the file is marked for update.

Returns:

0

Success

-1

An error occurred. errno is set to indicate the error.

Errors:

EBADF

Invalid file descriptor.

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 file system.

Examples:

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

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

    for( i = 1; i < argc; i++ ) {
      if( ( fd = open( argv[i], O_RDONLY ) ) == -1 ) {
        perror( argv[i] );
        ecode++;
      }
      else if( fchown( fd, getuid(), getgid() ) == -1 ) {
        perror( argv[i] );
        ecode++;
      }

      close( fd );
    }
    return( ecode );
  }

Classification:

POSIX 1003.1

See also:

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