chown() - Unix, Linux System Call
chown, fchown, lchown - change ownership of a file
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.
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
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.
path points outside your accessible address space.
Too many symbolic links were encountered in resolving
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.
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.
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.