chown(2) chown(2)
NAME [Toc] [Back]
chown(), fchown(), lchown() - change owner and group of a file
SYNOPSIS [Toc] [Back]
#include <unistd.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);
DESCRIPTION [Toc] [Back]
The chown() system call changes the user and group ownership of a
file. path points to the path name of a file. chown() sets the owner
ID and group ID of the file to the numeric values contained in owner
and group respectively. A value of UID_NO_CHANGE or GID_NO_CHANGE can
be specified in owner or group to leave unchanged the file's owner ID
or group ID, respectively. Note that owner and group should be less
than UID_MAX (see limits(5)).
Only processes with an effective user ID equal to the file owner or a
user having appropriate privileges can change the ownership of a file.
If privilege groups are supported, the owner of a file can change the
ownership only as a member of a privilege group allowing CHOWN, as set
up by the setprivgrp command (see setprivgrp(1M)). All users get the
CHOWN privilege by default.
The group ownership of a file can be changed to any group in the
current process's access list or to the real or effective group ID of
the current process. If privilege groups are supported and the user
has the CHOWN privilege, the file can be given to any group.
If chown() is invoked on a regular file by anyone other than the
superuser, the set-user-ID and set-group-ID bits of the file mode are
cleared. Whether chown() preserves or clears these bits on files of
other types is implementation dependent.
If the path given to chown() contains a symbolic link as the last
element, this link is traversed and path name resolution continues.
chown() changes the owner and group of the symbolic link's target,
rather than the owner and group of the link.
The fchown() system call functions exactly like chown(), except that
it operates on a file descriptor instead of a path name. fildes is a
file descriptor.
The lchown() system call sets the owner ID and group ID of the named
file just as chown() does, except in the case where the named file is
a symbolic link. In this case, lchown() changes the owner and group
of the symbolic link file itself.
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chown(2) chown(2)
Access Control Lists - HFS File Systems Only [Toc] [Back]
A user can allow or deny specific individuals and groups access to a
file by using the file's access control list (see acl(5)). When using
chown() in conjunction with HFS ACLs, if the new owner and/or group
does not have an optional ACL entry corresponding to user.% and/or
%.group in the file's access control list, the file's access
permission bits remain unchanged. However, if the new owner and/or
group is already designated by an optional ACL entry of user.% and/or
%.group, chown() sets the file's permission bits (and the three basic
ACL entries) to the permissions contained in that entry.
Access Control Lists - JFS File Systems Only [Toc] [Back]
A user can allow or deny specific individuals and groups access to a
file by using the file's access control list (see aclv(5)). When
using chown() in conjunction with JFS ACLs, if the new owner and/or
group of a file have optional ACL entries corresponding to
user:uid:perm and/or group:gid:perm in the file's access control list,
those entries remain in the ACL but no longer have any effect, being
superseded by the file's user::perm and/or group::perm entries.
RETURN VALUE [Toc] [Back]
chown() and fchown() return the following values:
0 Successful completion.
-1 Failure. The owner and group of the file remain unchanged.
errno is set to indicate the error.
ERRORS [Toc] [Back]
If chown() or lchown() fails, errno is set to one of the following
values:
[EACCES] Search permission is denied on a component of the
path prefix.
[EFAULT] path points outside the allocated address space of
the process. The reliable detection of this error
is implementation dependent.
[ELOOP] Too many symbolic links were encountered in
translating path.
[ENAMETOOLONG] A component of path exceeds NAME_MAX bytes while
_POSIX_NO_TRUNC is in effect, or path exceeds
PATH_MAX bytes.
[ENOENT] The file named by path does not exist.
[ENOTDIR] A component of the path prefix is not a directory.
[EINVAL] Either owner or group is greater than or equal to
UID_MAX, or is an illegal negative value.
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chown(2) chown(2)
[EPERM] The effective user ID is not a user having
appropriate privileges and one or more of the
following conditions exist:
+ The effective user ID does not match the owner
of the file.
+ When changing the owner of the file, the owner
of the file is not a member of a privilege
group allowing the CHOWN privilege.
+ When changing the group of the file, the owner
of the file is not a member of a privilege
group allowing the CHOWN privilege and the
group number is not in the current process's
access list.
[EROFS] The named file resides on a read-only file system.
If fchown() fails, errno is set to one of the following values:
[EBADF] fildes is not a valid file descriptor.
[EINVAL] Either owner or group is greater than or equal to
UID_MAX, or is an illegal negative value.
[EPERM] The effective user ID is not a user having
appropriate privileges and one or more of the
following conditions exist:
+ The effective user ID does not match the owner
of the file.
+ When changing the owner of the file, the owner
of the file is not a member of a privilege
group allowing the CHOWN privilege.
+ When changing the group of the file, the owner
of the file is not a member of a privilege
group allowing the CHOWN privilege and the
group number is not in the current process's
access list.
[EROFS] The named file resides on a read-only file system.
AUTHOR [Toc] [Back]
chown() was developed by AT&T.
fchown() was developed by the University of California, Berkeley.
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chown(2) chown(2)
SEE ALSO [Toc] [Back]
chown(1), setprivgrp(1M), chmod(2), setacl(2), acl(5), aclv(5),
limits(5).
STANDARDS CONFORMANCE [Toc] [Back]
chown(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1
fchown(): AES, SVID3
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