NAME
chown
, lchown
,
fchownat
, fchown
—
change owner and group of a file or
link
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);
#include <fcntl.h>
#include <unistd.h>
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 (or link) 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 superuser.By default,
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.
This behaviour can be overridden by setting the
sysctl(8)
variable fs.posix.setuid to zero.
lchown
()
operates similarly to how chown
() operated on older
systems, and does not follow symbolic links. It allows the owner and group
of a symbolic link to be set.
The
fchownat
()
function is equivalent to either the chown
() or
lchown
() function depending on the value of
flag (see below), except that where
path specifies a relative path, the file whose
ownership is changed is determined relative to the directory associated with
file descriptor fd instead of the current working
directory.
If
fchownat
()
is passed the special value AT_FDCWD
(defined in
<fcntl.h>
) in the
fd parameter, the current working directory is used
and the behavior is identical to a call to chown
()
or lchown
(), depending on whether or not the
AT_SYMLINK_NOFOLLOW
bit is set in
flag.
The flag argument is the bitwise OR of zero or more of the following values:
AT_SYMLINK_NOFOLLOW
- If path names a symbolic link, then the ownership of the symbolic link is changed.
fchown
()
is particularly useful when used in conjunction with the file locking
primitives (see flock(2)).
One of the owner or group IDs 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
chown
(), lchown
(),
and fchownat
() will fail and the file or link will
be unchanged if:
- [
ENOTDIR
] - A component of the path prefix is not a directory.
- [
ENAMETOOLONG
] - A component of a pathname exceeded
NAME_MAX
characters, or an entire pathname (including the terminating NUL) exceededPATH_MAX
bytes. - [
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 superuser.
- [
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.
Additionally, fchownat
() will fail if:
- [
EINVAL
] - The value of the flag argument was neither zero nor
AT_SYMLINK_NOFOLLOW
. - [
EBADF
] - The path argument specifies a relative path and the
fd argument is neither
AT_FDCWD
nor a valid file descriptor. - [
ENOTDIR
] - The path argument specifies a relative path and the fd argument is a valid file descriptor but it does not reference a directory.
- [
EACCES
] - The path argument specifies a relative path but search permission is denied for the directory which the fd file descriptor references.
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 superuser.
- [
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
STANDARDS
The chown
(),
fchown
(), fchownat
(), and
lchown
() functions are expected to conform to
IEEE Std 1003.1-2008 (“POSIX.1”).
HISTORY
The chown
() system call first appeared in
Version 1 AT&T UNIX. Since
Version 6 AT&T UNIX it supports changing
the group as well, and in Version 7 AT&T
UNIX group was made a separate argument.
The fchown
() system call first appeared in
4.1cBSD.
The chown
() and
fchown
() system calls were changed to follow
symbolic links in 4.4BSD; therefore, and for
compatibility with AT&T System V
Release 4 UNIX, the lchown
() system
call was added to OpenBSD 2.1.
The fchownat
() system call has been
available since OpenBSD 5.0.