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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 .