CHOWN(2)                      System Calls Manual                     CHOWN(2)

NAME
     chown, fchown, lchown, fchownat – change owner and group of a file

SYNOPSIS
     #include <unistd.h>

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

     int
     fchown(int fildes, uid_t owner, gid_t group);

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

     int
     fchownat(int fd, const char *path, uid_t owner, gid_t group, int flag);

DESCRIPTION
     The owner ID and group ID of the file named by path or referenced by
     fildes is changed as specified by the arguments owner and group.  The
     owner of a file may change the group to a group of which he or she is a
     member, but the change owner capability is restricted to the super-user.

     The chown() system call clears the set-user-id and set-group-id bits on
     the file.  The chown() system call follows symbolic links to operate on
     the target of the link rather than the link itself.

     The fchown() system call is particularly useful when used in conjunction
     with the file locking primitives (see flock(2)).

     The lchown() system call is similar to chown() but does not follow
     symbolic links.

     The fchownat() system call is equivalent to the chown() and lchown()
     except in the case where path specifies a relative path.  In this case
     the file to be changed is determined relative to the directory associated
     with the file descriptor fd instead of the current working directory.

     Values for flag are constructed by a bitwise-inclusive OR of flags from
     the following list, defined in <fcntl.h>:

     AT_SYMLINK_NOFOLLOW
             If path names a symbolic link, ownership of the symbolic link is
             changed.

     AT_SYMLINK_NOFOLLOW_ANY
             If path names a symbolic link, ownership of the symbolic link is
             changed.  If any any other symbolic link is encountered it is not
             followed and an error is returned instead.

     If fchownat() is passed the special value AT_FDCWD in the fd parameter,
     the current working directory is used and the behavior is identical to a
     call to chown() or lchown() respectively, depending on whether or not the
     AT_SYMLINK_NOFOLLOW bit is set in the flag argument.

     One of the owner or group id's may be left unchanged by specifying it as
     -1.

RETURN VALUES
     Upon successful completion, the value 0 is returned; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS
     The chown() and lchown() system calls will fail if:

     [EACCES]           Search permission is denied for a component of the
                        path prefix.

     [EFAULT]           The path argument points outside the process's
                        allocated address space.

     [ELOOP]            Too many symbolic links are encountered in translating
                        the pathname.  This is taken to be indicative of a
                        looping symbolic link.

     [ELOOP]            If AT_SYMLINK_NOFOLLOW_ANY is passed a symbolic link
                        was encountered in translating the pathname.

     [ENAMETOOLONG]     A component of a pathname exceeded 255 characters, or
                        an entire path name exceeded 1023 characters.

     [ENOENT]           A component of path does not exist.

     [ENOTDIR]          A component of the path prefix is not a directory.

     The fchown() system call will fail if:

     [EBADF]            The fildes argument does not refer to a valid
                        descriptor.

     [EINVAL]           The fildes argument refers to a socket, not a file.

     Any of these calls will fail if:

     [EINTR]            Its execution is interrupted by a signal.

     [EIO]              An I/O error occurs while reading from or writing to
                        the file system.

     [EPERM]            The effective user ID does not match the owner of the
                        file and the calling process does not have appropriate
                        (i.e., root) privileges.

     [EROFS]            The named file resides on a read-only file system.

     In addition to the errors specified for chown() and lchown(), the
     fchownat() system call may fail if:

     [EBADF]            The path argument does not specify an absolute path
                        and the fd argument is neither AT_FDCWD nor a valid
                        file descriptor open for searching.

     [EINVAL]           The value of the flag argument is not valid.

     [ENOTDIR]          The path argument is not an absolute path and fd is
                        neither AT_FDCWD nor a file descriptor associated with
                        a directory.

SEE ALSO
     chgrp(1), chmod(2), flock(2), chown(8)

STANDARDS
     The chown() system call is expected to conform to IEEE Std 1003.1-1990
     (“POSIX.1”).  The fchownat() system call is expected to conform to
     POSIX.1-2008 .

HISTORY
     The chown() function appeared in Version 7 AT&T UNIX.  The fchown()
     system call appeared in 4.2BSD.

     The chown() and fchown() system calls were changed to follow symbolic
     links in 4.4BSD.  The lchown() system call was added in FreeBSD 3.0 to
     compensate for the loss of functionality.

     The fchownat() system call appeared in OS X 10.10

macOS 15.2                      April 19, 1994                      macOS 15.2