1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
|
.\"
.\" Extended attributes system calls manual pages
.\"
.\" Copyright (C) Andreas Gruenbacher, February 2001
.\" Copyright (C) Silicon Graphics Inc, September 2001
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.TH GETXATTR 2 2001-12-01 "Linux" "Linux Programmer's Manual"
.SH NAME
getxattr, lgetxattr, fgetxattr \- retrieve an extended attribute value
.SH SYNOPSIS
.fam C
.nf
.B #include <sys/types.h>
.B #include <attr/xattr.h>
.sp
.BI "ssize_t getxattr(const char\ *" path ", const char\ *" name ,
.BI " void\ *" value ", size_t " size );
.BI "ssize_t lgetxattr(const char\ *" path ", const char\ *" name ,
.BI " void\ *" value ", size_t " size );
.BI "ssize_t fgetxattr(int " fd ", const char\ *" name ,
.BI " void\ *" value ", size_t " size );
.fi
.fam T
.SH DESCRIPTION
Extended attributes are
.IR name :\c
.I value
pairs associated with inodes (files, directories, symbolic links, etc.).
They are extensions to the normal attributes which are associated
with all inodes in the system (i.e., the
.BR stat (2)
data).
A complete overview of extended attributes concepts can be found in
.BR attr (5).
.PP
.BR getxattr ()
retrieves the
.I value
of the extended attribute identified by
.I name
and associated with the given
.I path
in the file system.
The length of the attribute
.I value
is returned.
.PP
.BR lgetxattr ()
is identical to
.BR getxattr (),
except in the case of a symbolic link, where the link itself is
interrogated, not the file that it refers to.
.PP
.BR fgetxattr ()
is identical to
.BR getxattr (),
only the open file referred to by
.I fd
(as returned by
.BR open (2))
is interrogated in place of
.IR path .
.PP
An extended attribute
.I name
is a simple null-terminated string.
The name includes a namespace prefix; there may be several, disjoint
namespaces associated with an individual inode.
The value of an extended attribute is a chunk of arbitrary textual or
binary data of specified length.
.PP
An empty buffer of
.I size
zero can be passed into these calls to return the current size of the
named extended attribute, which can be used to estimate the size of a
buffer which is sufficiently large to hold the value associated with
the extended attribute.
.PP
The interface is designed to allow guessing of initial buffer
sizes, and to enlarge buffers when the return value indicates
that the buffer provided was too small.
.SH RETURN VALUE
On success, a positive number is returned indicating the size of the
extended attribute value.
On failure, \-1 is returned and
.I errno
is set appropriately.
.PP
If the named attribute does not exist, or the process has no access to
this attribute,
.I errno
is set to
.BR ENOATTR .
.PP
If the
.I size
of the
.I value
buffer is too small to hold the result,
.I errno
is set to
.BR ERANGE .
.PP
If extended attributes are not supported by the file system, or are disabled,
.I errno
is set to
.BR ENOTSUP .
.PP
The errors documented for the
.BR stat (2)
system call are also applicable here.
.SH VERSIONS
These system calls have been available on Linux since kernel 2.4;
glibc support is provided since version 2.3.
.SH "CONFORMING TO"
These system calls are Linux-specific.
.\" .SH AUTHORS
.\" Andreas Gruenbacher,
.\" .RI < a.gruenbacher@computer.org >
.\" and the SGI XFS development team,
.\" .RI < linux-xfs@oss.sgi.com >.
.\" Please send any bug reports or comments to these addresses.
.SH SEE ALSO
.BR getfattr (1),
.BR setfattr (1),
.BR listxattr (2),
.BR open (2),
.BR removexattr (2),
.BR setxattr (2),
.BR stat (2),
.BR attr (5),
.BR symlink (7)
.SH COLOPHON
This page is part of release 3.27 of the Linux
.I man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
|
