CHOWN(1P) POSIX Programmer's Manual CHOWN(1P)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.
NAMEchown — change the file ownership
SYNOPSISchown [−h] owner[:group] file...
chown −R [−H|−L|−P] owner[:group] file...
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 encoun‐
tered while walking the directory trees specified by the file operands,
the chown utility shall perform actions equivalent to the chown() func‐
tion defined in the System Interfaces volume of POSIX.1‐2008, 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.
The chown utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported by the implementation:
−h 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 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.
−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 speci‐
fied 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. The chown util‐
ity 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 op‐
erand 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.
The following operands shall be supported:
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 data‐
base 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.
The following environment variables shall affect the execution of
LANG Provide a default value for the internationalization vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables 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).
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard
NLSPATH Determine the location of message catalogs for the processing
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
0 The utility executed successfully and all requested changes were
>0 An error occurred.
CONSEQUENCES OF ERRORS
The following sections are informative.
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 appropri‐
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 refer‐
ences to functions in the System Interfaces volume of POSIX.1‐2008. 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 POSIX.1‐2008 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 POSIX.1‐2008 because the <period> is a valid character in login
names (as specified by the Base Definitions volume of POSIX.1‐2008,
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 depar‐
ture 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 function‐
ality. However, the −R option was deemed an important user conve‐
nience, is far more efficient than forking a separate process for each
element of the directory hierarchy, and is in widespread historical
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1‐2008, chown()COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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
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