112 lines
2.2 KiB
HTML
112 lines
2.2 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 NULL</TITLE>
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</HEAD><BODY>
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<H1>NULL</H1>
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Section: Linux Programmer's Manual (4)<BR>Updated: 2015-07-23<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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null, zero - data sink
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<A NAME="lbAC"> </A>
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<H2>DESCRIPTION</H2>
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Data written to the
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<I>/dev/null</I>
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and
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<I>/dev/zero</I>
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special files is discarded.
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<P>
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Reads from
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<I>/dev/null</I>
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always return end of file (i.e.,
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<B><A HREF="/cgi-bin/man/man2html?2+read">read</A></B>(2)
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returns 0), whereas reads from
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<I>/dev/zero</I>
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always return bytes containing zero ('\0' characters).
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<P>
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These devices are typically created by:
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<P>
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mknod -m 666 /dev/null c 1 3
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mknod -m 666 /dev/zero c 1 5
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chown root:root /dev/null /dev/zero
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<A NAME="lbAD"> </A>
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<H2>FILES</H2>
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<I>/dev/null</I>
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<BR>
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<I>/dev/zero</I>
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<A NAME="lbAE"> </A>
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<H2>NOTES</H2>
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If these devices are not writable and readable for all users, many
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programs will act strangely.
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<P>
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Since Linux 2.6.31,
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reads from
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<I>/dev/zero</I>
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are interruptible by signals.
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(This change was made to help with bad latencies for large reads from
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<I>/dev/zero</I>.)
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<A NAME="lbAF"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+chown">chown</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+mknod">mknod</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?4+full">full</A></B>(4)
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<A NAME="lbAG"> </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="1"><A HREF="#lbAB">NAME</A><DD>
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<DT id="2"><A HREF="#lbAC">DESCRIPTION</A><DD>
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<DT id="3"><A HREF="#lbAD">FILES</A><DD>
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<DT id="4"><A HREF="#lbAE">NOTES</A><DD>
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<DT id="5"><A HREF="#lbAF">SEE ALSO</A><DD>
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<DT id="6"><A HREF="#lbAG">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: 00:06:02 GMT, March 31, 2021
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</BODY>
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</HTML>
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