185 lines
4.2 KiB
HTML
185 lines
4.2 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 FFLUSH</TITLE>
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</HEAD><BODY>
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<H1>FFLUSH</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2017-09-15<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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fflush - flush a stream
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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/stdio.h">stdio.h</A>></B>
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<P>
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<B>int fflush(FILE *</B><I>stream</I><B>);</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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For output streams,
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<B>fflush</B>()
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forces a write of all user-space buffered data for the given output or update
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<I>stream</I>
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via the stream's underlying write function.
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<P>
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For input streams associated with seekable files
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(e.g., disk files, but not pipes or terminals),
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<B>fflush</B>()
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discards any buffered data that has been fetched from the underlying file,
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but has not been consumed by the application.
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<P>
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The open status of the stream is unaffected.
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<P>
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If the
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<I>stream</I>
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argument is NULL,
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<B>fflush</B>()
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flushes
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<I>all</I>
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open output streams.
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<P>
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For a nonlocking counterpart, see
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<B><A HREF="/cgi-bin/man/man2html?3+unlocked_stdio">unlocked_stdio</A></B>(3).
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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Upon successful completion 0 is returned.
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Otherwise,
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<B>EOF</B>
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is returned and
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<I>errno</I>
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is set to indicate the error.
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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>EBADF</B>
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<DD>
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<I>stream</I>
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is not an open stream, or is not open for writing.
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</DL>
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<P>
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The function
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<B>fflush</B>()
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may also fail and set
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<I>errno</I>
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for any of the errors specified for
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<B><A HREF="/cgi-bin/man/man2html?2+write">write</A></B>(2).
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<A NAME="lbAG"> </A>
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<H2>ATTRIBUTES</H2>
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For an explanation of the terms used in this section, see
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<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
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<TABLE BORDER>
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<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>fflush</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
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</TABLE>
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<A NAME="lbAH"> </A>
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<H2>CONFORMING TO</H2>
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C89, C99, POSIX.1-2001, POSIX.1-2008.
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<P>
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POSIX.1-2001 did not specify the behavior for flushing of input streams,
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but the behavior is specified in POSIX.1-2008.
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<A NAME="lbAI"> </A>
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<H2>NOTES</H2>
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Note that
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<B>fflush</B>()
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flushes only the user-space buffers provided by the C library.
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To ensure that the data is physically stored on disk
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the kernel buffers must be flushed too, for example, with
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<B><A HREF="/cgi-bin/man/man2html?2+sync">sync</A></B>(2)
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or
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<B><A HREF="/cgi-bin/man/man2html?2+fsync">fsync</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?2+fsync">fsync</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+sync">sync</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+write">write</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?3+fclose">fclose</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+fileno">fileno</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+fopen">fopen</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+setbuf">setbuf</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+unlocked_stdio">unlocked_stdio</A></B>(3)
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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">ATTRIBUTES</A><DD>
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<DT id="8"><A HREF="#lbAH">CONFORMING TO</A><DD>
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<DT id="9"><A HREF="#lbAI">NOTES</A><DD>
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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: 00:05:42 GMT, March 31, 2021
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</BODY>
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</HTML>
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