chown, fchown, lchown — change ownership of a file
#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) ; |
These system calls change the owner and group of the file
specified by path
or
by fd
. Only a
privileged process (Linux: one with the CAP_CHOWN
capability) 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. A
privileged process (Linux: with CAP_CHOWN
) 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-superuser, 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
().
On success, zero is returned. On error, −1 is
returned, and errno
is set
appropriately.
Depending on the file system, other errors can be
returned. The more general errors for chown
() are listed below.
Search permission is denied on a component of the path prefix. (See also path_resolution(7).)
path
points
outside your accessible address space.
Too many symbolic links were encountered in
resolving path
.
path
is too
long.
The file does not exist.
Insufficient kernel memory was available.
A component of the path prefix is not a directory.
The calling process did not have the required permissions (see above) to change owner and/or group.
The named file resides on a read-only file system.
The general errors for fchown
() are listed below:
The descriptor is not valid.
A low-level I/O error occurred while modifying the inode.
See above.
See above.
See above.
4.4BSD, SVr4, POSIX.1-2001.
The 4.4BSD version can only be used by the superuser (that is, ordinary users cannot give away files).
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.
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 _BSD_SOURCE
is defined.
chmod(2), fchownat(2), flock(2), path_resolution(7)
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