CHOWN
NAME
chown, fchown, lchown - change ownership of a file
SYNOPSIS
#include <sys/types.h>
#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);
DESCRIPTION
The owner of the file specified by
path
or by
fd
is changed. Only the super-user may change the owner of a file. The owner
of a file may change the group of the file to any group of which that owner
is a member. The super-user may change the group arbitrarily.
If the
owner
or
group
is specified as -1, then that ID is not changed.
When the owner or group of an executable file are changed by a non-super-user,
the S_ISUID and S_ISGID mode bits are cleared. POSIX does not specify whether
this also should happen when root does the
chown;
the Linux behaviour depends on the kernel version.
In case of a non-group-executable file (with clear S_IXGRP bit)
the S_ISGID bit indicates mandatory locking, and is not cleared
by a
chown.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and
errno
is set appropriately.
ERRORS
Depending on the file system, other errors can be returned. The more
general errors for
chown
are listed below:
- EPERM
-
The effective UID does not match the owner of the file, and is not zero; or
the
owner
or
group
were specified incorrectly.
- EROFS
-
The named file resides on a read-only file system.
- EFAULT
-
path
points outside your accessible address space.
- ENAMETOOLONG
-
path
is too long.
- ENOENT
-
The file does not exist.
- ENOMEM
-
Insufficient kernel memory was available.
- ENOTDIR
-
A component of the path prefix is not a directory.
- EACCES
-
Search permission is denied on a component of the path prefix.
- ELOOP
-
Too many symbolic links were encountered in resolving
path.
The general errors for
fchown
are listed below:
- EBADF
-
The descriptor is not valid.
- ENOENT
-
See above.
- EPERM
-
See above.
- EROFS
-
See above.
- EIO
-
A low-level I/O error occurred while modifying the inode.
NOTES
In versions of Linux prior to 2.1.81 (and distinct from 2.1.46),
chown
did not follow symbolic links.
Since Linux 2.1.81,
chown
does follow symbolic links, and there is a new system call
lchown
that does not follow symbolic links.
Since Linux 2.1.86, this new call (that has the same semantics
as the old
chown)
has got the same syscall number, and
chown
got the newly introduced number.
The prototype for
fchown
is only available if
__USE_BSD
is defined.
CONFORMING TO
The
chown
call conforms to SVr4, SVID, POSIX, X/OPEN. The 4.4BSD version can only be
used by the superuser (that is, ordinary users cannot give away files).
SVr4 documents EINVAL, EINTR, ENOLINK and EMULTIHOP returns, but no
ENOMEM. POSIX.1 does not document ENOMEM or ELOOP error conditions.
The
fchown
call conforms to 4.4BSD and SVr4.
SVr4 documents additional EINVAL, EIO, EINTR, and ENOLINK error conditions.
RESTRICTIONS
The chown() semantics are deliberately violated on NFS file systems
which have UID mapping enabled. Additionally, the semantics of all system
calls which access the file contents are violated, because chown()
may cause immediate access revocation on already open files. Client side
caching may lead to a delay between the time where ownership have
been changed to allow access for a user and the time where the file can
actually be accessed by the user on other clients.
SEE ALSO
chmod(2),
flock(2)