.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "CHOWN" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" chown 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
chown \- change the file ownership
.SH SYNOPSIS
.LP
\fBchown\fP \fB[\fP\fB-hR\fP\fB]\fP \fIowner\fP\fB[\fP\fB:\fP\fIgroup\fP\fB]\fP
\fIfile\fP \fB...
.br
.sp
chown -R\fP \fB[\fP\fB-H | -L | -P\fP \fB]\fP \fIowner\fP\fB[\fP\fB:\fP\fIgroup\fP\fB]\fP
\fIfile\fP \fB...
.br
\fP
.SH DESCRIPTION
.LP
The \fIchown\fP utility shall set the user ID of the file named by
each \fIfile\fP operand to the user ID specified by the
\fIowner\fP operand.
.LP
For each \fIfile\fP operand, or, if the \fB-R\fP option is used, each
file encountered while walking the directory trees
specified by the \fIfile\fP operands, the \fIchown\fP utility shall
perform actions equivalent to the \fIchown\fP() function defined in
the System Interfaces volume of IEEE\ Std\ 1003.1-2001,
called with the following arguments:
.IP " 1." 4
The \fIfile\fP operand shall be used as the \fIpath\fP argument.
.LP
.IP " 2." 4
The user ID indicated by the \fIowner\fP portion of the first operand
shall be used as the \fIowner\fP argument.
.LP
.IP " 3." 4
If the \fIgroup\fP portion of the first operand is given, the group
ID indicated by it shall be used as the \fIgroup\fP
argument; otherwise, the group ownership shall not be changed.
.LP
.LP
Unless \fIchown\fP is invoked by a process with appropriate privileges,
the set-user-ID and set-group-ID bits of a regular file
shall be cleared upon successful completion; the set-user-ID and set-group-ID
bits of other file types may be cleared.
.SH OPTIONS
.LP
The \fIchown\fP utility shall conform to the Base Definitions volume
of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
.LP
The following options shall be supported by the implementation:
.TP 7
\fB-h\fP
If the system supports user IDs for symbolic links, for each \fIfile\fP
operand that names a file of type symbolic link,
\fIchown\fP shall attempt to set the user ID of the symbolic link.
If the system supports group IDs for symbolic links, and a
group ID was specified, for each \fIfile\fP operand that names a file
of type symbolic link, \fIchown\fP shall attempt to set the
group ID of the symbolic link. If the system does not support user
or group IDs for symbolic links, for each \fIfile\fP operand
that names a file of type symbolic link, \fIchown\fP shall do nothing
more with the current file and shall go on to any remaining
files.
.TP 7
\fB-H\fP
If the \fB-R\fP option is specified and a symbolic link referencing
a file of type directory is specified on the command line,
\fIchown\fP shall change the user ID (and group ID, if specified)
of the directory referenced by the symbolic link and all files
in the file hierarchy below it.
.TP 7
\fB-L\fP
If the \fB-R\fP option is specified and a symbolic link referencing
a file of type directory is specified on the command line
or encountered during the traversal of a file hierarchy, \fIchown\fP
shall change the user ID (and group ID, if specified) of the
directory referenced by the symbolic link and all files in the file
hierarchy below it.
.TP 7
\fB-P\fP
If the \fB-R\fP option is specified and a symbolic link is specified
on the command line or encountered during the traversal
of a file hierarchy, \fIchown\fP shall change the owner ID (and group
ID, if specified) of the symbolic link if the system
supports this operation. The \fIchown\fP utility shall not follow
the symbolic link to any other part of the file hierarchy.
.TP 7
\fB-R\fP
Recursively change file user and group IDs. For each \fIfile\fP operand
that names a directory, \fIchown\fP shall change the
user ID (and group ID, if specified) of the directory and all files
in the file hierarchy below it. Unless a \fB-H\fP, \fB-L\fP,
or \fB-P\fP option is specified, it is unspecified which of these
options will be used as the default.
.sp
.LP
Specifying more than one of the mutually-exclusive options \fB-H\fP,
\fB-L\fP, and \fB-P\fP shall not be considered an error.
The last option specified shall determine the behavior of the utility.
.SH OPERANDS
.LP
The following operands shall be supported:
.TP 7
\fIowner\fP\fB[\fP:\fIgroup\fP\fB]\fP
A user ID and optional group ID to be assigned to \fIfile\fP. The
\fIowner\fP portion of this operand shall be a user name
from the user database or a numeric user ID. Either specifies a user
ID which shall be given to each file named by one of the
\fIfile\fP operands. If a numeric \fIowner\fP operand exists in the
user database as a user name, the user ID number associated
with that user name shall be used as the user ID. Similarly, if the
\fIgroup\fP portion of this operand is present, it shall be a
group name from the group database or a numeric group ID. Either specifies
a group ID which shall be given to each file. If a
numeric group operand exists in the group database as a group name,
the group ID number associated with that group name shall be
used as the group ID.
.TP 7
\fIfile\fP
A pathname of a file whose user ID is to be modified.
.sp
.SH STDIN
.LP
Not used.
.SH INPUT FILES
.LP
None.
.SH ENVIRONMENT VARIABLES
.LP
The following environment variables shall affect the execution of
\fIchown\fP:
.TP 7
\fILANG\fP
Provide a default value for the internationalization variables that
are unset or null. (See the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
for
the precedence of internationalization variables used to determine
the values of locale categories.)
.TP 7
\fILC_ALL\fP
If set to a non-empty string value, override the values of all the
other internationalization variables.
.TP 7
\fILC_CTYPE\fP
Determine the locale for the interpretation of sequences of bytes
of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments).
.TP 7
\fILC_MESSAGES\fP
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
.TP 7
\fINLSPATH\fP
Determine the location of message catalogs for the processing of \fILC_MESSAGES
\&.\fP 
.sp
.SH ASYNCHRONOUS EVENTS
.LP
Default.
.SH STDOUT
.LP
Not used.
.SH STDERR
.LP
The standard error shall be used only for diagnostic messages.
.SH OUTPUT FILES
.LP
None.
.SH EXTENDED DESCRIPTION
.LP
None.
.SH EXIT STATUS
.LP
The following exit values shall be returned:
.TP 7
\ 0
The utility executed successfully and all requested changes were made.
.TP 7
>0
An error occurred.
.sp
.SH CONSEQUENCES OF ERRORS
.LP
Default.
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
Only the owner of a file or the user with appropriate privileges may
change the owner or group of a file.
.LP
Some implementations restrict the use of \fIchown\fP to a user with
appropriate privileges.
.SH EXAMPLES
.LP
None.
.SH RATIONALE
.LP
The System V and BSD versions use different exit status codes. Some
implementations used the exit status as a count of the
number of errors that occurred; this practice is unworkable since
it can overflow the range of valid exit status values. These are
masked by specifying only 0 and >0 as exit values.
.LP
The functionality of \fIchown\fP is described substantially through
references to functions in the System Interfaces volume of
IEEE\ Std\ 1003.1-2001. In this way, there is no duplication of effort
required for describing the interactions of
permissions, multiple groups, and so on.
.LP
The 4.3 BSD method of specifying both owner and group was included
in this volume of IEEE\ Std\ 1003.1-2001 because:
.IP " *" 3
There are cases where the desired end condition could not be achieved
using the \fIchgrp\fP and \fIchown\fP (that only changed the user
ID) utilities. (If the current owner is not
a member of the desired group and the desired owner is not a member
of the current group, the \fIchown\fP() function could fail unless
both owner and group are changed at the same time.)
.LP
.IP " *" 3
Even if they could be changed independently, in cases where both are
being changed, there is a 100% performance penalty caused
by being forced to invoke both utilities.
.LP
.LP
The BSD syntax \fIuser\fP[. \fIgroup\fP] was changed to \fIuser\fP[:
\fIgroup\fP] in this volume of
IEEE\ Std\ 1003.1-2001 because the period is a valid character in
login names (as specified by the Base Definitions volume
of IEEE\ Std\ 1003.1-2001, login names consist of characters in the
portable filename character set). The colon character
was chosen as the replacement for the period character because it
would never be allowed as a character in a user name or group
name on historical implementations.
.LP
The \fB-R\fP option is considered by some observers as an undesirable
departure from the historical UNIX system tools approach;
since a tool, \fIfind\fP, already exists to recurse over directories,
there seemed to be no
good reason to require other tools to have to duplicate that functionality.
However, the \fB-R\fP option was deemed an important
user convenience, is far more efficient than forking a separate process
for each element of the directory hierarchy, and is in
widespread historical use.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIchmod\fP, \fIchgrp\fP, the System Interfaces volume of
IEEE\ Std\ 1003.1-2001, \fIchown\fP()
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .