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.\"     @(#)chown.2	8.4 (Berkeley) 4/19/94
.\"
.Dd April 19, 1994
.Dt CHOWN 2
.Os BSD 4
.Sh NAME
.Nm chown ,
.Nm fchown
.Nd change owner and group of a file
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fn chown "const char *path" "uid_t owner" "gid_t group"
.Ft int
.Fn fchown "int fd" "uid_t owner" "gid_t group"
.Sh DESCRIPTION
The owner ID and group ID of the file
named by
.Fa path
or referenced by
.Fa fd
is changed as specified by the arguments
.Fa owner
and 
.Fa group .
The owner of a file may change the
.Fa group
to a group of which
he or she is a member,
but the change
.Fa owner
capability is restricted to the super-user.
.Pp
.Fn Chown
clears the set-user-id and set-group-id bits
on the file
to prevent accidental or mischievous creation of
set-user-id and set-group-id programs if not executed
by the super-user.
.Pp
.Fn Fchown
is particularly useful when used in conjunction
with the file locking primitives (see
.Xr flock 2 ) .
.Pp
One of the owner or group id's
may be left unchanged by specifying it as -1.
.Sh RETURN VALUES
Zero is returned if the operation was successful;
-1 is returned if an error occurs, with a more specific
error code being placed in the global variable
.Va errno .
.Sh ERRORS
.Fn Chown
will fail and the file will be unchanged if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er EINVAL
The pathname contains a character with the high-order bit set.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 characters.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EPERM
The effective user ID is not the super-user.
.It Bq Er EROFS
The named file resides on a read-only file system.
.It Bq Er EFAULT
.Fa Path
points outside the process's allocated address space.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Pp
.Fn Fchown
will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
.Fa Fd
does not refer to a valid descriptor.
.It Bq Er EINVAL
.Fa Fd
refers to a socket, not a file.
.It Bq Er EPERM
The effective user ID is not the super-user.
.It Bq Er EROFS
The named file resides on a read-only file system.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr chown 8 ,
.Xr chgrp 1 ,
.Xr chmod 2 ,
.Xr flock 2
.Sh STANDARDS
.Fn Chown
is expected to conform to IEEE Std 1003.1-1988
.Pq Dq Tn POSIX .
.Sh HISTORY
The
.Fn fchown
function call
appeared in
.Bx 4.2 .
.Pp
The
.Fn chown
and
.Fn fchown
functions were changed to follow symbolic links in
.Bx 4.4 .