CHOWN(2) BSD System Calls Manual CHOWN(2)NAME
chown, lchown, fchown — change owner and group of a file
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <unistd.h>
int
chown(const char *path, uid_t owner, gid_t group);
int
lchown(const char *path, uid_t owner, gid_t group);
int
fchown(int fd, uid_t owner, gid_t group);
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.
When called to change the owner of a file, chown(), lchown() and fchown()
clear the set-user-id (S_ISUID) bit on the file. When a called to change
the group of a file, chown(), lchown() and fchown() clear the set-group-
id (S_ISGID) bit on the file. These actions are taken to prevent acci‐
dental or mischievous creation of set-user-id and set-group-id programs.
lchown() is like chown() except in the case where the named file is a
symbolic link, in which case lchown() changes the owner and group of the
link, while chown() changes the owner and group of the file the link ref‐
erences.
fchown() is particularly useful when used in conjunction with the file
locking primitives (see flock(2)).
One of the owner or group id's may be left unchanged by specifying it as
(uid_t)-1 or (gid_t)-1 respectively.
RETURN VALUES
Zero is returned if the operation was successful; -1 is returned if an
error occurs, with a more specific error code being placed in the global
variable errno.
ERRORSchown() and lchown() will fail and the file will be unchanged if:
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} charac‐
ters, or an entire path name exceeded {PATH_MAX} char‐
acters.
[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 translat‐
ing 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 ALSOchgrp(1), chmod(2), flock(2), symlink(7), chown(8)STANDARDS
The chown() function deviates from the semantics defined in ISO/IEC
9945-1:1990 (“POSIX.1”), which specifies that, unless the caller is the
super-user, both the set-user-id and set-group-id bits on a file shall be
cleared, regardless of the file attribute changed. The lchown() and
fchown() functions, as defined by X/Open Portability Guide Issue 4,
Version 2 (“XPG4.2”), provide the same semantics.
To retain conformance to these standards, compatibility interfaces are
provided by the POSIX Compatibility Library (libposix, -lposix) as fol‐
lows:
· The chown() function conforms to ISO/IEC 9945-1:1990 (“POSIX.1”) and
X/Open Portability Guide Issue 4, Version 2 (“XPG4.2”).
· The lchown() and fchown() functions conform to X/Open Portability
Guide Issue 4, Version 2 (“XPG4.2”).
HISTORY
The fchown() function call appeared in 4.2BSD.
The chown() and fchown() functions were changed to follow symbolic links
in 4.4BSD. The lchown() function call appeared in NetBSD 1.3.
BSD April 19, 1994 BSD
