.\" Copyright (C) Andreas Gruenbacher, February 2001
.\" Copyright (C) Silicon Graphics Inc, September 2001
.\"
.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
.\" 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, see
.\" <http://www.gnu.org/licenses/>.
.\" %%%LICENSE_END
.\"
.TH LISTXATTR 2 2013-04-09 "Linux" "Linux Programmer's Manual"
.SH NAME
listxattr, llistxattr, flistxattr \- list extended attribute names
.SH SYNOPSIS
.fam C
.nf
.B #include <sys/types.h>
.B #include <attr/xattr.h>
.sp
.BI "ssize_t listxattr(const char\ *" path ", char\ *" list \
", size_t " size );
.BI "ssize_t llistxattr(const char\ *" path ", char\ *" list \
", size_t " size );
.BI "ssize_t flistxattr(int " fd ", char\ *" list ", size_t " size );
.fi
.fam T
.SH DESCRIPTION
Extended attributes are name: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 listxattr ()
retrieves the list
of extended attribute names associated with the given
.I path
in the filesystem.
The retrieved list is placed in
.IR list ,
a caller-allocated buffer whose size (in bytes) is specified in the argument
.IR size .
The list is the set of (null-terminated) names, one after the other.
Names of extended attributes to which the calling process does not
have access may be omitted from the list.
The length of the attribute name
.I list
is returned.
.PP
.BR llistxattr ()
is identical to
.BR listxattr (),
except in the case of a symbolic link, where the list of names of
extended attributes associated with the link itself is retrieved,
not the file that it refers to.
.PP
.BR flistxattr ()
is identical to
.BR listxattr (),
only the open file referred to by
.I fd
(as returned by
.BR open (2))
is interrogated in place of
.IR path .
.PP
A single 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.
.PP
An empty buffer of
.I size
zero can be passed into these calls to return the current size of the
list of extended attribute names, which can be used to estimate the
size of a buffer which is sufficiently large to hold the list of names.
.SS Example
The
.I list
of names is returned as an unordered array of null-terminated character
strings (attribute names are separated by null bytes (\(aq\\0\(aq)), like this:
.fam C
.RS
.nf

user.name1\\0system.name1\\0user.name2\\0
.fi
.RE
.fam T
.P
Filesystems like ext2, ext3 and XFS which implement POSIX ACLs using
extended attributes, might return a
.I list
like this:
.fam C
.RS
.nf

system.posix_acl_access\\0system.posix_acl_default\\0
.fi
.RE
.fam T
.SH RETURN VALUE
On success, a nonnegative number is returned indicating the size of the
extended attribute name list.
On failure, \-1 is returned and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B ENOTSUP
Extended attributes are not supported by the filesystem, or are disabled.
.TP
.B ERANGE
The
.I size
of the
.I list
buffer is too small to hold the result.
.PP
In addition, the errors documented in
.BR stat (2)
can also occur.
.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 getxattr (2),
.BR open (2),
.BR removexattr (2),
.BR setxattr (2),
.BR stat (2),
.BR attr (5),
.BR symlink (7)