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.\"
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.\" Extended attributes system calls manual pages
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.\"
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.\" (C) Andreas Gruenbacher, February 2001
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.\" (C) Silicon Graphics Inc, September 2001
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.\"
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, write to the Free
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.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
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.\" USA.
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.\"
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.TH LISTXATTR 2 "Extended Attributes" "Dec 2001" "Linux Programmer's Manual"
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.SH NAME
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listxattr, llistxattr, flistxattr \- list extended attribute names
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.SH SYNOPSIS
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.fam C
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.nf
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.B #include <sys/types.h>
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.B #include <attr/xattr.h>
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.sp
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.BI "ssize_t listxattr (const char\ *" path ",
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.BI "\t\t\t\t char\ *" list ", size_t " size );
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.BI "ssize_t llistxattr (const char\ *" path ",
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.BI "\t\t\t\t char\ *" list ", size_t " size );
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.BI "ssize_t flistxattr (int " filedes ",
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.BI "\t\t\t\t char\ *" list ", size_t " size );
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.fi
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.fam T
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.SH DESCRIPTION
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Extended attributes are name:value
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pairs associated with inodes (files, directories, symlinks, etc).
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They are extensions to the normal attributes which are associated
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with all inodes in the system (i.e. the
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.BR stat (2)
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data).
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A complete overview of extended attributes concepts can be found in
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.BR attr (5).
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.PP
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2005-10-19 06:54:38 +00:00
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.BR listxattr ()
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retrieves the
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.I list
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of extended attribute names associated with the given
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.I path
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in the filesystem.
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The list is the set of (null-terminated) names, one after the other.
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Names of extended attributes to which the calling process does not
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have access may be omitted from the list.
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The length of the attribute name
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.I list
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is returned.
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.PP
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2005-10-19 06:54:38 +00:00
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.BR llistxattr ()
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is identical to
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.BR listxattr (),
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except in the case of a symbolic link, where the list of names of
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extended attributes associated with the link itself is retrieved,
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not the file that it refers to.
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.PP
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2005-10-19 06:54:38 +00:00
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.BR flistxattr ()
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is identical to
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.BR listxattr (),
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only the open file pointed to by
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.I filedes
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(as returned by
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.BR open (2))
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is interrogated in place of
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.IR path .
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.PP
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A single extended attribute
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.I name
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is a simple null-terminated string.
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The name includes a namespace prefix; there may be several, disjoint
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namespaces associated with an individual inode.
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.PP
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An empty buffer of
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.I size
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zero can be passed into these calls to return the current size of the
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list of extended attribute names, which can be used to estimate the
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size of a buffer which is sufficiently large to hold the list of names.
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.SH EXAMPLES
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The
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.I list
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of names is returned as an unordered array of null-terminated character
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strings (attribute names are separated by null bytes ('\\0')), like this:
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.fam C
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.RS
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.nf
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user.name1\\0system.name1\\0user.name2\\0
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.fi
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.RE
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.fam T
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.P
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Filesystems like ext2, ext3 and XFS which implement POSIX ACLs using
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extended attributes, might return a
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.I list
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like this:
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.fam C
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.RS
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.nf
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system.posix_acl_access\\0system.posix_acl_default\\0
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.fi
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.RE
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.fam T
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.SH RETURN VALUE
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On success, a positive number is returned indicating the size of the
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extended attribute name list.
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On failure, \-1 is returned and
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.I errno
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is set appropriately.
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.PP
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If the
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.I size
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of the
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.I list
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buffer is too small to hold the result,
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.I errno
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is set to ERANGE.
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.PP
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If extended attributes are not supported by the filesystem, or are disabled,
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.I errno
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is set to ENOTSUP.
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.PP
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The errors documented for the
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.BR stat (2)
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system call are also applicable here.
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.SH AUTHORS
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Andreas Gruenbacher,
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.RI < a.gruenbacher@computer.org >
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and the SGI XFS development team,
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.RI < linux-xfs@oss.sgi.com >.
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Please send any bug reports or comments to these addresses.
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.SH SEE ALSO
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.BR getfattr (1),
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.BR setfattr (1),
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.BR getxattr (2),
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.BR open (2),
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.BR removexattr (2),
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.BR setxattr (2),
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.BR stat (2),
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.BR attr (5)
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