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.\"     @(#)chown.2	8.4 (Berkeley) 4/19/94
.\"
.Dd $Mdocdate: May 31 2007 $
.Dt CHOWN 2
.Os
.Sh NAME
.Nm chown ,
.Nm lchown ,
.Nm fchown
.Nd change owner and group of a file or link
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <unistd.h>
.Ft int
.Fn chown "const char *path" "uid_t owner" "gid_t group"
.Ft int
.Fn lchown "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 (or link) 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 superuser.
.Pp
By default,
.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.
This behaviour can be overridden by setting the
.Xr sysctl 8
variable
.Va fs.posix.setuid
to zero.
.Pp
.Fn lchown
operates similarly to how
.Fn chown
operated on older systems, and does not follow symbolic links.
It allows the owner and group of a symbolic link to be set.
.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 IDs
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
or
.Fn lchown
will fail and the file or link 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 ENAMETOOLONG
A component of a pathname exceeded
.Dv {NAME_MAX}
characters, or an entire path name exceeded
.Dv {PATH_MAX}
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 superuser.
.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 superuser.
.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 chgrp 1 ,
.Xr chmod 2 ,
.Xr flock 2 ,
.Xr chown 8
.Sh STANDARDS
The
.Fn chown
function is expected to conform to
.St -p1003.1-88 .
.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 .
.Pp
The
.Fn lchown
function was added to
.Ox
due to the above.