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() and fchown() functions set 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() and fchown() do 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
(does not start with a "/"), 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
AT_SYMLINK_NOFOLLOW, 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 {B_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(5) or user_attr(5).
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(5) and fpathconf(2).

Upon successful completion, chown(), fchown(), lchown(), and fchownat()
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 chown() and fchownat() functions will fail if:

EBADF For fchown(), the fildes argument is not an open file
descriptor.

For fchownat(), the path argument is not absolute and
the fildes argument is neither AT_FDCWD, nor 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.

INTERFACE STABILITY


Committed

MT-LEVEL
Async-Signal-Safe

SEE ALSO


chgrp(1), chown(1), chmod(2), fpathconf(2), system(5), attributes(7),
standards(7)

OmniOS March 13, 2021 OmniOS