262 lines
6.2 KiB
HTML
262 lines
6.2 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 UNAME</TITLE>
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</HEAD><BODY>
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<H1>UNAME</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2019-10-10<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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uname - get name and information about current kernel
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/sys/utsname.h">sys/utsname.h</A>></B>
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<P>
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<B>int uname(struct utsname *</B><I>buf</I><B>);</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>uname</B>()
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returns system information in the structure pointed to by
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<I>buf</I>.
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The
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<I>utsname</I>
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struct is defined in
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<I><<A HREF="file:///usr/include/sys/utsname.h">sys/utsname.h</A>></I>:
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<P>
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struct utsname {
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<BR> char sysname[]; /* Operating system name (e.g., "Linux") */
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<BR> char nodename[]; /* Name within "some implementation-defined
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<BR> network" */
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<BR> char release[]; /* Operating system release (e.g., "2.6.28") */
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<BR> char version[]; /* Operating system version */
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<BR> char machine[]; /* Hardware identifier */
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#ifdef _GNU_SOURCE
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<BR> char domainname[]; /* NIS or YP domain name */
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#endif
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};
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<P>
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The length of the arrays in a
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<I>struct utsname</I>
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is unspecified (see NOTES);
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the fields are terminated by a null byte ('\0').
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success, zero is returned.
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On error, -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>EFAULT</B>
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<DD>
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<I>buf</I>
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is not valid.
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</DL>
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<A NAME="lbAG"> </A>
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<H2>CONFORMING TO</H2>
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POSIX.1-2001, POSIX.1-2008, SVr4.
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There is no
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<B>uname</B>()
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call in 4.3BSD.
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<P>
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The
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<I>domainname</I>
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member (the NIS or YP domain name) is a GNU extension.
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<A NAME="lbAH"> </A>
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<H2>NOTES</H2>
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This is a system call, and the operating system presumably knows
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its name, release and version.
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It also knows what hardware it runs on.
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So, four of the fields of the struct are meaningful.
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On the other hand, the field
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<I>nodename</I>
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is meaningless:
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it gives the name of the present machine in some undefined
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network, but typically machines are in more than one network
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and have several names.
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Moreover, the kernel has no way of knowing
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about such things, so it has to be told what to answer here.
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The same holds for the additional
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<I>domainname</I>
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field.
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<P>
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To this end, Linux uses the system calls
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<B><A HREF="/cgi-bin/man/man2html?2+sethostname">sethostname</A></B>(2)
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and
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<B><A HREF="/cgi-bin/man/man2html?2+setdomainname">setdomainname</A></B>(2).
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Note that there is no standard that says that the hostname set by
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<B><A HREF="/cgi-bin/man/man2html?2+sethostname">sethostname</A></B>(2)
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is the same string as the
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<I>nodename</I>
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field of the struct returned by
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<B>uname</B>()
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(indeed, some systems allow a 256-byte hostname and an 8-byte nodename),
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but this is true on Linux.
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The same holds for
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<B><A HREF="/cgi-bin/man/man2html?2+setdomainname">setdomainname</A></B>(2)
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and the
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<I>domainname</I>
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field.
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<P>
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The length of the fields in the struct varies.
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Some operating systems
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or libraries use a hardcoded 9 or 33 or 65 or 257.
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Other systems use
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<B>SYS_NMLN</B>
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or
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<B>_SYS_NMLN</B>
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or
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<B>UTSLEN</B>
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or
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<B>_UTSNAME_LENGTH</B>.
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Clearly, it is a bad
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idea to use any of these constants; just use sizeof(...).
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Often 257 is chosen in order to have room for an internet hostname.
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<P>
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Part of the utsname information is also accessible via
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<I>/proc/sys/kernel/</I>{<I>ostype</I>,
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<I>hostname</I>,
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<I>osrelease</I>,
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<I>version</I>,
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<I>domainname</I>}.
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<A NAME="lbAI"> </A>
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<H3>C library/kernel differences</H3>
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<P>
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Over time, increases in the size of the
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<I>utsname</I>
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structure have led to three successive versions of
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<B>uname</B>():
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<I>sys_olduname</I>()
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(slot
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<I>__NR_oldolduname</I>),
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<I>sys_uname</I>()
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(slot
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<I>__NR_olduname</I>),
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and
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<I>sys_newuname</I>()
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(slot
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<I>__NR_uname)</I>.
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The first one
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used length 9 for all fields;
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the second
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used 65;
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the third also uses 65 but adds the
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<I>domainname</I>
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field.
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The glibc
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<B>uname</B>()
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wrapper function hides these details from applications,
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invoking the most recent version of the system call provided by the kernel.
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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+uname">uname</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?2+getdomainname">getdomainname</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+gethostname">gethostname</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?7+uts_namespaces">uts_namespaces</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="2"><A HREF="#lbAB">NAME</A><DD>
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<DT id="3"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="4"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="5"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="6"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="7"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="8"><A HREF="#lbAH">NOTES</A><DD>
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<DL>
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<DT id="9"><A HREF="#lbAI">C library/kernel differences</A><DD>
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</DL>
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<DT id="10"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="11"><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: 00:05:35 GMT, March 31, 2021
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</BODY>
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