lchown(2)
NAME
chown, lchown, fchown, fchownat - change owner and group of
a file
SYNOPSIS
#include <unistd.h>
#include <sys/types.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 fildes, uid_t owner, gid_t group);
int fchownat(int fildes, const char *path, uid_t owner,
gid_t group, int flag);
DESCRIPTION
The chown() function sets the owner ID and group ID of the
file specified by path or referenced by the open file
descriptor fildes to owner and group respectively. If owner
or group is specified as -1, chown() does not change the
corresponding ID of the file.
The lchown() function sets the owner ID and group ID of the
named file in the same manner as chown(), unless the named
file is a symbolic link. In this case, lchown() changes the
ownership of the symbolic link file itself, while chown()
changes the ownership of the file or directory to which the
symbolic link refers.
The fchownat() function sets the owner ID and group ID of
the named file in the same manner as chown(). If, however,
the path argument is relative, the path is resolved relative
to the fildes argument rather than the current working
directory. If the fildes argument has the special value
FDCWD, the path path resolution reverts back to current
working directory relative. If the flag argument is set to
SYMLNK, the function behaves like lchown() with respect to
symbolic links. If the path argument is absolute, the fildes
argument is ignored. If the path argument is a null
pointer, the function behaves like fchown().
If chown(), lchown(), fchown(), or fchownat() is invoked by
a process other than super-user, the set-user-ID and set-
group-ID bits of the file mode, S_ISUID and S_ISGID respec-
tively, are cleared (see chmod(2)).
The operating system provides a configuration option,
{_POSIX_CHOWN_RESTRICTED}, to restrict ownership changes for
the chown(), lchown(), and fchown() functions. When
{_POSIX_CHOWN_RESTRICTED} is not in effect, either the
effective user ID of the process must match the owner of the
file or the process must be the super-user to change the
ownership of a file. When {_POSIX_CHOWN_RESTRICTED} is in
effect (the default behavior), the chown(), lchown(), and
fchown() functions, for users other than super-user, prevent
the owner of the file from changing the owner ID of the
file and restrict the change of the group of the file to the
list of supplementary group IDs. To set this configuration
option, include the following line in /etc/system:
set rstchown = 1
To disable this option, include the following line in
/etc/system:
set rstchown = 0
See system(4) and fpathconf(2).
Upon successful completion, chown(), fchown() and lchown()
mark for update the st_ctime field of the file.
RETURN VALUES
Upon successful completion, 0 is returned. Otherwise, -1 is
returned, the owner and group of the named file remain
unchanged, and errno is set to indicate the error.
ERRORS
The chown(), lchown(), and fchownat()functions will fail if:
EACCES
Search permission is denied on a component of the path
prefix of path.
EFAULT
The path argument points to an illegal address and for
fchownat(), the file descriptor has the value
AT_FDCWD.
EINTR A signal was caught during the execution of the
chown() or lchown() function.
EINVAL
The group or owner argument is out of range.
EIO An I/O error occurred while reading from or writing to
the file system.
ELOOP Too many symbolic links were encountered in translat-
ing path.
ENAMETOOLONG
The length of the path argument exceeds {PATH_MAX}, or
the length of a path component exceeds {NAME_MAX}
while {_POSIX_NO_TRUNC} is in effect.
ENOLINK
The path argument points to a remote machine and the
link to that machine is no longer active.
ENOENT
Either a component of the path prefix or the file
referred to by path does not exist or is a null path-
name.
ENOTDIR
A component of the path prefix of path is not a direc-
tory, or the path supplied to fchownat() is relative
and the file descriptor provided does not refer to a
valid directory.
EPERM The effective user ID does not match the owner of the
file or the process is not the super-user and
_POSIX_CHOWN_RESTRICTED indicates that such privilege
is required.
EROFS The named file resides on a read-only file system.
The fchown() and fchownat() functions will fail if:
EBADF For fchown() the fildes argument is not an open file
descriptor and.
EBADF For fchownat(), the path argument is not absolute and
the fildes argument is not AT_FDCWD or an open file
descriptor.
EIO An I/O error occurred while reading from or writing to
the file system.
EINTR A signal was caught during execution of the function.
ENOLINK
The fildes argument points to a remote machine and the
link to that machine is no longer active.
EINVAL
The group or owner argument is out of range.
EPERM The effective user ID does not match the owner of the
file, or the process is not the super-user and
_POSIX_CHOWN_RESTRICTED indicates that such privilege
is required.
EROFS The named file referred to by fildes resides on a
read-only file system.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| ___________________________|_____________________________|__
| Interface Stability | chown() is Standard|
| | fchownat() is Evolving |
| ____________________________|_____________________________|_
| MT-Level | chown() and fchownat() are|
| | Async-Signal-Safe |
|_____________________________|_____________________________|
SEE ALSO
chgrp(1), chown(1), chmod(2), fpathconf(2), system(4),
attributes (5)
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