[apple/xnu.git] / bsd / man / man2 / setxattr.2

.\"
.\" Copyright (c) 2004 Apple Computer, Inc. All rights reserved.
.\"
.\" @APPLE_LICENSE_HEADER_START@
.\"
.\" This file contains Original Code and/or Modifications of Original Code
.\" as defined in and that are subject to the Apple Public Source License
.\" Version 2.0 (the 'License'). You may not use this file except in
.\" compliance with the License. Please obtain a copy of the License at
.\" http://www.opensource.apple.com/apsl/ and read it before using this
.\" file.
.\"
.\" The Original Code and all software distributed under the License are
.\" distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
.\" EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
.\" INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
.\" FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
.\" Please see the License for the specific language governing rights and
.\" limitations under the License.
.\"
.\" @APPLE_LICENSE_HEADER_END@
.\"
.Dd Oct 19, 2004
.Dt SETXATTR 2
.Os "Mac OS X"
.Sh NAME
.Nm setxattr,
.Nm fsetxattr
.Nd set an extended attribute value
.Sh SYNOPSIS
.Fd #include <sys/xattr.h>
.Ft int
.Fn setxattr "const char *path" "const char *name" "void *value" "size_t size" "u_int32_t position" "int options"
.Ft int
.Fn fsetxattr "int fd" "const char *name" "void *value" "size_t size" "u_int32_t position" "int options"
.Sh DESCRIPTION
Extended attributes extend the basic attributes associated with files and
directories in the file system.  They are stored as name:data pairs
associated with file system objects (files, directories, symlinks, etc).
.Pp
.Fn setxattr
associates
.Fa name
and
.Fa data
together as an attribute of
.Fa path .
.Pp
An extended attribute's
.Fa name
is a simple NULL-terminated UTF-8 string.
.Fa Value
is a pointer to a data buffer of
.Fa size
bytes containing textual or binary data to be associated with the
extended attribute.
.Fa Position
specifies the offset within the extended attribute.  In the current
implementation, only the resource fork extended attribute makes use of
this argument.  For all others,
.Fa position
is reserved and should be
set to zero.
.Pp
.Fa options
controls how the attribute is set:
.Pp
.Bl -tag -width XATTR_NOFOLLOW
.It Dv XATTR_NOFOLLOW
do not follow symbolic links.
.Fn setxattr
normally sets attributes on the target of
.Fa path
if it is a symbolic link.
With this option,
.Fn setxattr
will act on the link itself.
.It Dv XATTR_CREATE
fail if the named attribute already exists.
.It Dv XATTR_REPLACE
fail if the named attribute does not exist.  Failure to specify
.Dv XATTR_REPLACE
or
.Dv XATTR_CREATE
allows creation and replacement.
.El
.Pp
.Fn fsetxattr
is identical to
.Fn setxattr ,
except that it sets an extended attribute on an open file referenced by
file descriptor
.Fa fd .
.Sh NOTES
On some filesystems, such as
.Dv HFS+ ,
setting the extended attribute
.Dv com.apple.ResourceFork
will update the modification time (``mtime'') of
the file.
.Pp
Due to historical reasons, the
.Dv XATTR_FINDERINFO_NAME
(defined to be 
.Dq com.apple.FinderInfo )
extended attribute must be 32 bytes; see the
.Dv ATTR_CMN_FNDRINFO
section in
.Xr getattrlist 2 .
.Pp
The maximum supported size of extended attribute can be found out using 
.Xr pathconf 2 
with _PC_XATTR_SIZE_BITS option.  
.Sh RETURN VALUES
On success, 0 is returned.  On failure, -1 is returned and the global
variable
.Va errno
is set as follows.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EEXIST
.Fa options
contains
.Em XATTR_CREATE
and the named attribute already exists.
.It Bq Er ENOATTR
.Fa options
is set to
.Em XATTR_REPLACE
and the named attribute does not exist.
.It Bq Er ENOTSUP
The file system does not support extended attributes or has them disabled.
.It Bq Er EROFS
The file system is mounted read-only.
.It Bq Er ERANGE
The data size of the attribute is out of range (some attributes have size
restrictions).
.It Bq Er EPERM
.\" EFTYPE could be more specific but isn't POSIX
Attributes cannot be associated with this type of object.  For example,
attributes are not allowed for resource forks.
.It Bq Er EINVAL
.Fa name
or
.Fa options
is invalid.
.Fa name
must be valid UTF-8 and
.Fa options
must make sense.
.It Bq Er ENOTDIR
A component of
.Fa path
is not a directory.
.It Bq Er ENAMETOOLONG
.Fa name
exceeded
.Dv XATTR_MAXNAMELEN
UTF-8 bytes, or a component of
.Fa path
exceeded
.Dv NAME_MAX
characters, or the entire
.Fa path
exceeded
.Dv PATH_MAX
characters.
.It Bq Er EACCES
Search permission is denied for a component of
.Fa path
or permission to set the attribute is denied.
.It Bq Er ELOOP
Too many symbolic links were encountered resolving
.Fa path .
.It Bq Er EFAULT
.Fa path
or
.Fa name
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.It Bq Er E2BIG
The data size of the extended attribute is too large.
.It Bq Er ENOSPC
Not enough space left on the file system.
.El
.Sh SEE ALSO
.Xr getxattr 2 ,
.Xr listxattr 2 ,
.Xr removexattr 2 ,
.Xr pathconf 2
.Sh HISTORY
.Fn setxattr
and
.Fn fsetxattr
first appeared in Mac OS X 10.4.
Commit	Line	Data
91447636 A	1	.\"
	2	.\" Copyright (c) 2004 Apple Computer, Inc. All rights reserved.
	3	.\"
6601e61a	4	.\" @APPLE_LICENSE_HEADER_START@
91447636	5	.\"
8f6c56a5 A	6	.\" This file contains Original Code and/or Modifications of Original Code
	7	.\" as defined in and that are subject to the Apple Public Source License
	8	.\" Version 2.0 (the 'License'). You may not use this file except in
	9	.\" compliance with the License. Please obtain a copy of the License at
	10	.\" http://www.opensource.apple.com/apsl/ and read it before using this
91447636 A	11	.\" file.
91447636 A	12	.\"
8f6c56a5 A	13	.\" The Original Code and all software distributed under the License are
	14	.\" distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	15	.\" EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	16	.\" INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	17	.\" FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
	18	.\" Please see the License for the specific language governing rights and
91447636 A	19	.\" limitations under the License.
91447636 A	20	.\"
6601e61a	21	.\" @APPLE_LICENSE_HEADER_END@
91447636 A	22	.\"
	23	.Dd Oct 19, 2004
	24	.Dt SETXATTR 2
	25	.Os "Mac OS X"
	26	.Sh NAME
	27	.Nm setxattr,
	28	.Nm fsetxattr
	29	.Nd set an extended attribute value
	30	.Sh SYNOPSIS
	31	.Fd #include <sys/xattr.h>
	32	.Ft int
	33	.Fn setxattr "const char path" "const char name" "void *value" "size_t size" "u_int32_t position" "int options"
	34	.Ft int
	35	.Fn fsetxattr "int fd" "const char name" "void value" "size_t size" "u_int32_t position" "int options"
	36	.Sh DESCRIPTION
	37	Extended attributes extend the basic attributes associated with files and
	38	directories in the file system. They are stored as name:data pairs
	39	associated with file system objects (files, directories, symlinks, etc).
	40	.Pp
	41	.Fn setxattr
	42	associates
	43	.Fa name
	44	and
	45	.Fa data
	46	together as an attribute of
	47	.Fa path .
	48	.Pp
	49	An extended attribute's
	50	.Fa name
	51	is a simple NULL-terminated UTF-8 string.
	52	.Fa Value
	53	is a pointer to a data buffer of
	54	.Fa size
	55	bytes containing textual or binary data to be associated with the
	56	extended attribute.
	57	.Fa Position
	58	specifies the offset within the extended attribute. In the current
	59	implementation, only the resource fork extended attribute makes use of
	60	this argument. For all others,
	61	.Fa position
	62	is reserved and should be
	63	set to zero.
	64	.Pp
	65	.Fa options
	66	controls how the attribute is set:
	67	.Pp
	68	.Bl -tag -width XATTR_NOFOLLOW
	69	.It Dv XATTR_NOFOLLOW
	70	do not follow symbolic links.
	71	.Fn setxattr
	72	normally sets attributes on the target of
	73	.Fa path
	74	if it is a symbolic link.
	75	With this option,
	76	.Fn setxattr
	77	will act on the link itself.
	78	.It Dv XATTR_CREATE
	79	fail if the named attribute already exists.
	80	.It Dv XATTR_REPLACE
	81	fail if the named attribute does not exist. Failure to specify
	82	.Dv XATTR_REPLACE
	83	or
	84	.Dv XATTR_CREATE
	85	allows creation and replacement.
86	.El
87	.Pp
88	.Fn fsetxattr
89	is identical to
90	.Fn setxattr ,
91	except that it sets an extended attribute on an open file referenced by
92	file descriptor
93	.Fa fd .
39236c6e	94	.Sh NOTES
6d2010ae A	95	On some filesystems, such as
	96	.Dv HFS+ ,
	97	setting the extended attribute
	98	.Dv com.apple.ResourceFork
	99	will update the modification time (``mtime'') of
	100	the file.
39236c6e A	101	.Pp
	102	Due to historical reasons, the
	103	.Dv XATTR_FINDERINFO_NAME
	104	(defined to be
	105	.Dq com.apple.FinderInfo )
	106	extended attribute must be 32 bytes; see the
	107	.Dv ATTR_CMN_FNDRINFO
	108	section in
	109	.Xr getattrlist 2 .
	110	.Pp
	111	The maximum supported size of extended attribute can be found out using
	112	.Xr pathconf 2
	113	with _PC_XATTR_SIZE_BITS option.
91447636 A	114	.Sh RETURN VALUES
	115	On success, 0 is returned. On failure, -1 is returned and the global
	116	variable
	117	.Va errno
	118	is set as follows.
	119	.Sh ERRORS
	120	.Bl -tag -width Er
	121	.It Bq Er EEXIST
	122	.Fa options
	123	contains
	124	.Em XATTR_CREATE
	125	and the named attribute already exists.
	126	.It Bq Er ENOATTR
	127	.Fa options
	128	is set to
	129	.Em XATTR_REPLACE
	130	and the named attribute does not exist.
	131	.It Bq Er ENOTSUP
	132	The file system does not support extended attributes or has them disabled.
	133	.It Bq Er EROFS
	134	The file system is mounted read-only.
	135	.It Bq Er ERANGE
	136	The data size of the attribute is out of range (some attributes have size
	137	restrictions).
	138	.It Bq Er EPERM
	139	.\" EFTYPE could be more specific but isn't POSIX
	140	Attributes cannot be associated with this type of object. For example,
	141	attributes are not allowed for resource forks.
	142	.It Bq Er EINVAL
	143	.Fa name
	144	or
	145	.Fa options
	146	is invalid.
	147	.Fa name
	148	must be valid UTF-8 and
	149	.Fa options
	150	must make sense.
	151	.It Bq Er ENOTDIR
	152	A component of
	153	.Fa path
	154	is not a directory.
	155	.It Bq Er ENAMETOOLONG
	156	.Fa name
	157	exceeded
	158	.Dv XATTR_MAXNAMELEN
	159	UTF-8 bytes, or a component of
	160	.Fa path
	161	exceeded
	162	.Dv NAME_MAX
	163	characters, or the entire
	164	.Fa path
	165	exceeded
	166	.Dv PATH_MAX
	167	characters.
	168	.It Bq Er EACCES
	169	Search permission is denied for a component of
	170	.Fa path
	171	or permission to set the attribute is denied.
	172	.It Bq Er ELOOP
	173	Too many symbolic links were encountered resolving
	174	.Fa path .
	175	.It Bq Er EFAULT
	176	.Fa path
	177	or
178	.Fa name
179	points to an invalid address.
180	.It Bq Er EIO
181	An I/O error occurred while reading from or writing to the file system.
182	.It Bq Er E2BIG
183	The data size of the extended attribute is too large.
184	.It Bq Er ENOSPC
185	Not enough space left on the file system.
186	.El
187	.Sh SEE ALSO
188	.Xr getxattr 2 ,
2d21ac55	189	.Xr listxattr 2 ,
39236c6e A	190	.Xr removexattr 2 ,
39236c6e A	191	.Xr pathconf 2
91447636 A	192	.Sh HISTORY
	193	.Fn setxattr
	194	and
	195	.Fn fsetxattr
	196	first appeared in Mac OS X 10.4.