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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>tcdrain</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_009_435"> </a>NAME</h4><blockquote>tcdrain - wait for transmission of output</blockquote><h4><a name = "tag_000_009_436"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="termios.h.html">termios.h</a>>int tcdrain(int <i>fildes</i>);</code></pre></blockquote><h4><a name = "tag_000_009_437"> </a>DESCRIPTION</h4><blockquote>The<i>tcdrain()</i>function waits until all output written to the object referred to by<i>fildes</i>is transmitted. The<i>fildes</i>argument is an open file descriptor associated with a terminal.<p>Any attempts to use<i>tcdrain()</i>from a process which is a member of a background process group on a<i>fildes</i>associated with its controlling terminal, will cause the process group to besent a SIGTTOU signal. If the calling process is blocking or ignoring SIGTTOUsignals, the process is allowed to perform the operation, and no signal issent.</blockquote><h4><a name = "tag_000_009_438"> </a>RETURN VALUE</h4><blockquote>Upon successful completion, 0 is returned. Otherwise, -1 is returned and<i>errno</i>is set to indicate the error.</blockquote><h4><a name = "tag_000_009_439"> </a>ERRORS</h4><blockquote>The<i>tcdrain()</i>function will fail if:<dl compact><dt>[EBADF]<dd>The<i>fildes</i>argument is not a valid file descriptor.<dt>[EINTR]<dd>A signal interrupted<i>tcdrain()</i>.<dt>[ENOTTY]<dd>The file associated with<i>fildes</i>is not a terminal.</dl><p>The<i>tcdrain()</i>function may fail if:<dl compact><dt>[EIO]<dd>The process group of the writing process is orphaned,and the writing process is not ignoring or blocking SIGTTOU.</dl></blockquote><h4><a name = "tag_000_009_440"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_009_441"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_009_442"> </a>FUTURE DIRECTIONS</h4><blockquote>In the ISO POSIX-1 standard, the possibility of an [EIO] error occurring isdescribed in <b>XBD</b> specification, <a href="../xbd/termios.html#tag_008_001_004"><b>Terminal Access Control</b> </a>, but it is not mentioned in the<i>tcdrain()</i>interface definition.It has become clear that this omission was unintended,so it is likely that the [EIO] error will be reclassified asa "will fail" in a future issue of the POSIX standard.</blockquote><h4><a name = "tag_000_009_443"> </a>SEE ALSO</h4><blockquote><i><a href="tcflush.html">tcflush()</a></i>,<i><a href="termios.h.html"><termios.h></a></i>,<i><a href="unistd.h.html"><unistd.h></a></i>,the <b>XBD</b> specification, <a href="../xbd/termios.html"><b>General Terminal Interface</b> </a>.</blockquote><h4>DERIVATION</h4><blockquote>Derived from the POSIX.1-1988 standard.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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