man-pages/man3/isatty.3.html
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<H1>ISATTY</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>
isatty - test whether a file descriptor refers to a terminal
<A NAME="lbAC">&nbsp;</A>
<H2>SYNOPSIS</H2>
<PRE>
<B>#include &lt;<A HREF="file:///usr/include/unistd.h">unistd.h</A>&gt;</B>
<B>int isatty(int </B><I>fd</I><B>);</B>
</PRE>
<A NAME="lbAD">&nbsp;</A>
<H2>DESCRIPTION</H2>
The
<B>isatty</B>()
function tests whether
<I>fd</I>
is an open file descriptor referring to a terminal.
<A NAME="lbAE">&nbsp;</A>
<H2>RETURN VALUE</H2>
<B>isatty</B>()
returns 1 if
<I>fd</I>
is an open file descriptor referring to a terminal;
otherwise 0 is returned, and
<I>errno</I>
is set to indicate the error.
<A NAME="lbAF">&nbsp;</A>
<H2>ERRORS</H2>
<DL COMPACT>
<DT id="1"><B>EBADF</B>
<DD>
<I>fd</I>
is not a valid file descriptor.
<DT id="2"><B>ENOTTY</B>
<DD>
<I>fd</I>
refers to a file other than a terminal.
On some older kernels, some types of files
resulted in the error
<B>EINVAL</B>
in this case (which is a violation of POSIX, which specifies the error
<B>ENOTTY</B>).
</DL>
<A NAME="lbAG">&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>isatty</B>()
</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
</TABLE>
<A NAME="lbAH">&nbsp;</A>
<H2>CONFORMING TO</H2>
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
<A NAME="lbAI">&nbsp;</A>
<H2>SEE ALSO</H2>
<B><A HREF="/cgi-bin/man/man2html?2+fstat">fstat</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?3+ttyname">ttyname</A></B>(3)
<A NAME="lbAJ">&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="3"><A HREF="#lbAB">NAME</A><DD>
<DT id="4"><A HREF="#lbAC">SYNOPSIS</A><DD>
<DT id="5"><A HREF="#lbAD">DESCRIPTION</A><DD>
<DT id="6"><A HREF="#lbAE">RETURN VALUE</A><DD>
<DT id="7"><A HREF="#lbAF">ERRORS</A><DD>
<DT id="8"><A HREF="#lbAG">ATTRIBUTES</A><DD>
<DT id="9"><A HREF="#lbAH">CONFORMING TO</A><DD>
<DT id="10"><A HREF="#lbAI">SEE ALSO</A><DD>
<DT id="11"><A HREF="#lbAJ">COLOPHON</A><DD>
</DL>
<HR>
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Time: 00:05:46 GMT, March 31, 2021
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