CHOWN(2) System Calls CHOWN(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 AT_FDCWD, the 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
that does not have {PRIV_FILE_SETID} asserted in its effective set, the
set-user-ID and set-group-ID bits of the file mode, S_ISUID and S_ISGID
respectively, are cleared (see chmod(2)). Additional restrictions apply
when changing the ownership to uid 0.


The operating system defines several privileges to override restrictions
on the chown() family of functions. When the {PRIV_FILE_CHOWN} privilege
is asserted in the effective set of the current process, there are no
restrictions except in the special circumstances of changing ownership to
or from uid 0. When the {PRIV_FILE_CHOWN_SELF} privilege is asserted,
ownership changes are restricted to the files of which the ownership
matches the effective user ID of the current process. If neither
privilege is asserted in the effective set of the calling process,
ownership changes are limited to changes of the group of the file to the
list of supplementary group IDs and the effective group ID.


The operating system provides a configuration option,
{_POSIX_CHOWN_RESTRICTED}, to control the default behavior of processes
and the behavior of the NFS server. If {_POSIX_CHOWN_RESTRICTED} is not
in effect, the privilege {PRIV_FILE_CHOWN_SELF} is asserted in the
inheritable set of all processes unless overridden by policy.conf(4) or
user_attr(4). 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


All of these functions will fail if:

EPERM
The effective user ID does not match the owner of the file and
the {PRIV_FILE_CHOWN} privilege is not asserted in the effective
set of the calling process, or the {PRIV_FILE_CHOWN_SELF}
privilege is not asserted in the effective set of the calling
process.


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 translating
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 pathname.


ENOTDIR
A component of the path prefix of path is not a
directory, or the path supplied to fchownat() is relative
and the file descriptor provided does not refer to a
valid directory.


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.

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.


EROFS
The named file referred to by fildes resides on a read-only
file system.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | See below. |
+--------------------+-----------------+
|MT-Level | See below. |
+--------------------+-----------------+


The chown(), fchown(), and lchown() functions are Standard. The
fchownat() function is Evolving.


The chown() and fchownat() functions are Async-Signal-Safe.

SEE ALSO


chgrp(1), chown(1), chmod(2), fpathconf(2), system(4), attributes(5),
standards(5)


October 9, 2008 CHOWN(2)