man-pages/man3/ferror.3.html
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<H1>FERROR</H1>
Section: Linux Programmer's Manual (3)<BR>Updated: 2019-03-06<BR><A HREF="#index">Index</A>
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB">&nbsp;</A>
<H2>NAME</H2>
clearerr, feof, ferror, fileno - check and reset stream status
<A NAME="lbAC">&nbsp;</A>
<H2>SYNOPSIS</H2>
<B>#include &lt;<A HREF="file:///usr/include/stdio.h">stdio.h</A>&gt;</B>
<P>
<B>void clearerr(FILE *</B><I>stream</I><B>);</B>
<P>
<B>int feof(FILE *</B><I>stream</I><B>);</B>
<P>
<B>int ferror(FILE *</B><I>stream</I><B>);</B>
<P>
<B>int fileno(FILE *</B><I>stream</I><B>);</B>
<P>
Feature Test Macro Requirements for glibc (see
<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
<P>
<B>fileno</B>():
_POSIX_C_SOURCE
<A NAME="lbAD">&nbsp;</A>
<H2>DESCRIPTION</H2>
The function
<B>clearerr</B>()
clears the end-of-file and error indicators for the stream pointed to by
<I>stream</I>.
<P>
The function
<B>feof</B>()
tests the end-of-file indicator for the stream pointed to by
<I>stream</I>,
returning nonzero if it is set.
The end-of-file indicator can be cleared only by the function
<B>clearerr</B>().
<P>
The function
<B>ferror</B>()
tests the error indicator for the stream pointed to by
<I>stream</I>,
returning nonzero if it is set.
The error indicator can be reset only by the
<B>clearerr</B>()
function.
<P>
The function
<B>fileno</B>()
examines the argument
<I>stream</I>
and returns the integer file descriptor used to implement this stream.
The file descriptor is still owned by
<I>stream</I>
and will be closed when
<B><A HREF="/cgi-bin/man/man2html?3+fclose">fclose</A></B>(3)
is called.
Duplicate the file descriptor with
<B><A HREF="/cgi-bin/man/man2html?2+dup">dup</A></B>(2)
before passing it to code that might close it.
<P>
For nonlocking counterparts, see
<B><A HREF="/cgi-bin/man/man2html?3+unlocked_stdio">unlocked_stdio</A></B>(3).
<A NAME="lbAE">&nbsp;</A>
<H2>ERRORS</H2>
These functions should not fail and do not set the external variable
<I>errno</I>.
(However, in case
<B>fileno</B>()
detects that its argument is not a valid stream, it must
return -1 and set
<I>errno</I>
to
<B>EBADF</B>.)
<A NAME="lbAF">&nbsp;</A>
<H2>ATTRIBUTES</H2>
For an explanation of the terms used in this section, see
<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
<TABLE BORDER>
<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
<TR VALIGN=top><TD>
<B>clearerr</B>(),
<B>feof</B>(),
<BR>
<B>ferror</B>(),
<B>fileno</B>()
</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
</TABLE>
<A NAME="lbAG">&nbsp;</A>
<H2>CONFORMING TO</H2>
The functions
<B>clearerr</B>(),
<B>feof</B>(),
and
<B>ferror</B>()
conform to C89, C99, POSIX.1-2001, and POSIX.1-2008.
<P>
The function
<B>fileno</B>()
conforms to POSIX.1-2001 and POSIX.1-2008.
<A NAME="lbAH">&nbsp;</A>
<H2>SEE ALSO</H2>
<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?3+fdopen">fdopen</A></B>(3),
<B><A HREF="/cgi-bin/man/man2html?3+stdio">stdio</A></B>(3),
<B><A HREF="/cgi-bin/man/man2html?3+unlocked_stdio">unlocked_stdio</A></B>(3)
<A NAME="lbAI">&nbsp;</A>
<H2>COLOPHON</H2>
This page is part of release 5.05 of the Linux
<I>man-pages</I>
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
<P>
<HR>
<A NAME="index">&nbsp;</A><H2>Index</H2>
<DL>
<DT id="1"><A HREF="#lbAB">NAME</A><DD>
<DT id="2"><A HREF="#lbAC">SYNOPSIS</A><DD>
<DT id="3"><A HREF="#lbAD">DESCRIPTION</A><DD>
<DT id="4"><A HREF="#lbAE">ERRORS</A><DD>
<DT id="5"><A HREF="#lbAF">ATTRIBUTES</A><DD>
<DT id="6"><A HREF="#lbAG">CONFORMING TO</A><DD>
<DT id="7"><A HREF="#lbAH">SEE ALSO</A><DD>
<DT id="8"><A HREF="#lbAI">COLOPHON</A><DD>
</DL>
<HR>
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