246 lines
6.0 KiB
HTML
246 lines
6.0 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of GETXATTR</TITLE>
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</HEAD><BODY>
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<H1>GETXATTR</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2019-03-06<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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getxattr, lgetxattr, fgetxattr - retrieve an extended attribute value
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/sys/types.h">sys/types.h</A>></B>
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<B>#include <<A HREF="file:///usr/include/sys/xattr.h">sys/xattr.h</A>></B>
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<B>ssize_t getxattr(const char *</B><I>path</I><B>, const char *</B><I>name</I><B>,</B>
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<B> void *</B><I>value</I><B>, size_t </B><I>size</I><B>);</B>
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<B>ssize_t lgetxattr(const char *</B><I>path</I><B>, const char *</B><I>name</I><B>,</B>
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<B> void *</B><I>value</I><B>, size_t </B><I>size</I><B>);</B>
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<B>ssize_t fgetxattr(int </B><I>fd</I><B>, const char *</B><I>name</I><B>,</B>
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<B> void *</B><I>value</I><B>, size_t </B><I>size</I><B>);</B>
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</PRE>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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Extended attributes are
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<I>name</I>:<I>value</I>
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pairs associated with inodes (files, directories, symbolic links, 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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<B><A HREF="/cgi-bin/man/man2html?2+stat">stat</A></B>(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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<B><A HREF="/cgi-bin/man/man2html?7+xattr">xattr</A></B>(7).
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<P>
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<B>getxattr</B>()
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retrieves the value of the extended attribute identified by
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<I>name</I>
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and associated with the given
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<I>path</I>
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in the filesystem.
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The attribute value is placed in the buffer pointed to by
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<I>value</I>;
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<I>size</I>
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specifies the size of that buffer.
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The return value of the call is the number of bytes placed in
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<I>value</I>.
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<P>
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<B>lgetxattr</B>()
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is identical to
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<B>getxattr</B>(),
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except in the case of a symbolic link, where the link itself is
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interrogated, not the file that it refers to.
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<P>
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<B>fgetxattr</B>()
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is identical to
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<B>getxattr</B>(),
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only the open file referred to by
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<I>fd</I>
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(as returned by
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2))
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is interrogated in place of
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<I>path</I>.
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<P>
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An extended attribute
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<I>name</I>
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is a 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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The value of an extended attribute is a chunk of arbitrary textual or
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binary data that was assigned using
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<B><A HREF="/cgi-bin/man/man2html?2+setxattr">setxattr</A></B>(2).
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<P>
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If
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<I>size</I>
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is specified as zero, these calls return the current size of the
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named extended attribute (and leave
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<I>value</I>
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unchanged).
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This can be used to determine the size of the buffer that
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should be supplied in a subsequent call.
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(But, bear in mind that there is a possibility that the
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attribute value may change between the two calls,
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so that it is still necessary to check the return status
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from the second call.)
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success, these calls return a nonnegative value which is
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the size (in bytes) of the extended attribute value.
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On failure, -1 is returned and
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<I>errno</I>
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is set appropriately.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="1"><B>E2BIG</B>
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<DD>
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The size of the attribute value is larger than the maximum size allowed; the
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attribute cannot be retrieved.
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This can happen on filesystems that support
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very large attribute values such as NFSv4, for example.
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<DT id="2"><B>ENODATA</B>
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<DD>
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The named attribute does not exist, or the process has no access to
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this attribute.
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<DT id="3"><B>ENOTSUP</B>
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<DD>
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Extended attributes are not supported by the filesystem, or are disabled.
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<DT id="4"><B>ERANGE</B>
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<DD>
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The
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<I>size</I>
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of the
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<I>value</I>
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buffer is too small to hold the result.
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</DL>
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<P>
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In addition, the errors documented in
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<B><A HREF="/cgi-bin/man/man2html?2+stat">stat</A></B>(2)
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can also occur.
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<A NAME="lbAG"> </A>
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<H2>VERSIONS</H2>
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These system calls have been available on Linux since kernel 2.4;
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glibc support is provided since version 2.3.
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<A NAME="lbAH"> </A>
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<H2>CONFORMING TO</H2>
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These system calls are Linux-specific.
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<A NAME="lbAI"> </A>
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<H2>EXAMPLE</H2>
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See
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<B><A HREF="/cgi-bin/man/man2html?2+listxattr">listxattr</A></B>(2).
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<A NAME="lbAJ"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+getfattr">getfattr</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+setfattr">setfattr</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?2+listxattr">listxattr</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+removexattr">removexattr</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+setxattr">setxattr</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+stat">stat</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?7+symlink">symlink</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+xattr">xattr</A></B>(7)
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<A NAME="lbAK"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="5"><A HREF="#lbAB">NAME</A><DD>
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<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="8"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="9"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="10"><A HREF="#lbAG">VERSIONS</A><DD>
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<DT id="11"><A HREF="#lbAH">CONFORMING TO</A><DD>
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<DT id="12"><A HREF="#lbAI">EXAMPLE</A><DD>
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<DT id="13"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="14"><A HREF="#lbAK">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:32 GMT, March 31, 2021
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</BODY>
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</HTML>
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