CHOWN(2)

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

LIBRARY
libc

SYNOPSIS
#include <unistd.h>
int
chown(const char *path, uid_t owner, gid_t group);
int
fchown(int fd, uid_t owner, gid_t group);
int
lchown(const char *path, uid_t owner, gid_t group);
int
fchownat(int dirfd, const char *path, uid_t owner, gid_t group, int flags);

DESCRIPTION
The owner ID and group ID of the file named by path or referenced by fd 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.

Chown() clears the set-user-id and set-group-id bits on the file to prevent accidental or mischievous creation of set-user-id and set-group-id programs if not executed by the super-user. chown() follows symbolic links to operate on the target of the link rather than the link itself.

Fchown() is particularly useful when used in conjunction with the file locking primitives (see flock(2)).

Lchown() is similar to chown() but does not follow symbolic links.

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

The fchownat() function is equivalent to the chown() or lchown() functions except in the case where the path specifies a relative path. In this case the file to be opened is determined relative to the directory associated with the file descriptor dirfd instead of the current working directory. If fchownat() is passed the special value AT_FDCWD in the dirfd parameter, the current working directory is used and the behavior is identical to a call to chown() or lchown().

The values for the flags 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, the mode of the symbolic link is changed.

RETURN VALUES

ERRORS
Chown(), lchown() and fchownat() will fail and the file will be unchanged if:

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

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

[ENOENT]
    The named file does not exist.

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

[ELOOP]
    Too many symbolic links were encountered in translating the pathname.

[EPERM]
    The effective user ID is not the super-user.

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

[EFAULT]
    Path points outside the process's allocated address space.

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

Fchown() will fail if:

[EBADF]
    fd does not refer to a valid descriptor.

[EINVAL]
    fd refers to a socket, not a file.

[EPERM]
    The effective user ID is not the super-user.

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

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

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

STANDARDS
The chown() function call is expected to conform to p1003.1-90.

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

The chown() function was changed to follow symbolic links in 4.4BSD. The lchown() function was added in FreeBSD 3.0 to compensate for the loss of functionality.

The fchownat() system call appeared in DragonFly 2.3.