System Calls chown(2)
NAME
chown, lchown, fchown, fchownat - change owner and group of
a file
SYNOPSIS
#include
#include
int chown(const char *path, uidt owner, gidt group);
int lchown(const char *path, uidt owner, gidt group);
int fchown(int fildes, uidt owner, gidt group);
int fchownat(int fildes, const char *path, uidt owner,
gidt 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
ATFDCWD, the path resolution reverts back to current work-
ing 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 {PRIVFILESETID} asserted in
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System Calls chown(2)
its effective set, the set-user-ID and set-group-ID bits of
the file mode, SISUID and SISGID 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
{PRIVFILECHOWN} 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 {PRIVFILECHOWNSELF} 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,
{POSIXCHOWNRESTRICTED}, to control the default behavior
of processes and the behavior of the NFS server. If
{POSIXCHOWNRESTRICTED} is not in effect, the privilege
{PRIVFILECHOWNSELF} is asserted in the inheritable set of
all processes unless overridden by policy.conf(4) or
userattr(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 stctime 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.
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System Calls chown(2)
ERORS
All of these functions will fail if:
EPERM The effective user ID does not match the owner of
the file and the {PRIVFILECHOWN} privilege is not
asserted in the effective set of the calling pro-
cess, or the {PRIVFILECHOWNSELF} privilege is
not asserted in the effective set of the calling
process.
The chown(), lchown(), and fchownat() functions will fail
if:
EACES 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 ATFDCWD.
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.
ELOP Too many symbolic links were encountered in
translating path.
ENAMETOLONG The length of the path argument exceeds
{PATHMAX}, or the length of a path com-
ponent exceeds {NAMEMAX} while
{POSIXNOTRUNC} 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
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System Calls chown(2)
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 descrip-
tor 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 ATFDCWD or an
open file descriptor.
EIO An I/O error occurred while reading from or writ-
ing to the file system.
EINTR A signal was caught during execution of the func-
tion.
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.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
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System Calls chown(2)
ATRIBUTE TYPE ATRIBUTE 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)
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