NAME
chown - change the file ownership
SYNOPSIS
chown [-hR] owner[:group] file ...
chown -R [-H | -L | -P ] owner[:group] file ...
DESCRIPTION
The chown utility shall set the user ID of the file named by each file
operand to the user ID specified by the owner operand.
For each file operand, or, if the -R option is used, each file
encountered while walking the directory trees specified by the file
operands, the chown utility shall perform actions equivalent to the
chown() function defined in the System Interfaces volume of
IEEE Std 1003.1-2001, called with the following arguments:
1. The file operand shall be used as the path argument.
2. The user ID indicated by the owner portion of the first operand
shall be used as the owner argument.
3. If the group portion of the first operand is given, the group ID
indicated by it shall be used as the group argument; otherwise, the
group ownership shall not be changed.
Unless chown 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.
OPTIONS
The chown utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported by the implementation:
-h If the system supports user IDs for symbolic links, for each
file operand that names a file of type symbolic link, chown
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 file operand that names a file of type
symbolic link, chown 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 file operand that names a file of
type symbolic link, chown shall do nothing more with the current
file and shall go on to any remaining files.
-H If the -R option is specified and a symbolic link referencing a
file of type directory is specified on the command line, chown
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.
-L If the -R 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, chown
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.
-P If the -R option is specified and a symbolic link is specified
on the command line or encountered during the traversal of a
file hierarchy, chown shall change the owner ID (and group ID,
if specified) of the symbolic link if the system supports this
operation. The chown utility shall not follow the symbolic link
to any other part of the file hierarchy.
-R Recursively change file user and group IDs. For each file
operand that names a directory, chown shall change the user ID
(and group ID, if specified) of the directory and all files in
the file hierarchy below it. Unless a -H, -L, or -P option is
specified, it is unspecified which of these options will be used
as the default.
Specifying more than one of the mutually-exclusive options -H, -L, and
-P shall not be considered an error. The last option specified shall
determine the behavior of the utility.
OPERANDS
The following operands shall be supported:
owner[:group]
A user ID and optional group ID to be assigned to file. The
owner 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 file operands.
If a numeric owner 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 group 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.
file A pathname of a file whose user ID is to be modified.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of
chown:
LANG 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.)
LC_ALL If set to a non-empty string value, override the values of all
the other internationalization variables.
LC_CTYPE
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).
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard error.
NLSPATH
Determine the location of message catalogs for the processing of
LC_MESSAGES .
ASYNCHRONOUS EVENTS
Default.
STDOUT
Not used.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 The utility executed successfully and all requested changes were
made.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
Only the owner of a file or the user with appropriate privileges may
change the owner or group of a file.
Some implementations restrict the use of chown to a user with
appropriate privileges.
EXAMPLES
None.
RATIONALE
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.
The functionality of chown 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.
The 4.3 BSD method of specifying both owner and group was included in
this volume of IEEE Std 1003.1-2001 because:
* There are cases where the desired end condition could not be
achieved using the chgrp and chown (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 chown() function could fail unless both owner and group are
changed at the same time.)
* 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.
The BSD syntax user[. group] was changed to user[: group] 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.
The -R option is considered by some observers as an undesirable
departure from the historical UNIX system tools approach; since a tool,
find, 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 -R 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.
FUTURE DIRECTIONS
None.
SEE ALSO
chmod , chgrp , the System Interfaces volume of IEEE Std 1003.1-2001,
chown()
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 .