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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>tcflow</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_444"> </a>NAME</h4><blockquote>tcflow - suspend or restart the transmission or reception of data</blockquote><h4><a name = "tag_000_009_445"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="termios.h.html">termios.h</a>>int tcflow(int <i>fildes</i>, int <i>action</i>);</code></pre></blockquote><h4><a name = "tag_000_009_446"> </a>DESCRIPTION</h4><blockquote>The<i>tcflow()</i>function suspends transmission or reception of data on the objectreferred to by<i>fildes</i>,depending on the value of<i>action</i>.The<i>fildes</i>argument is an open file descriptor associated with a terminal.<ul><p><li>If<i>action</i>is TCOOFF, output is suspended.<p><li>If<i>action</i>is TCOON, suspended output is restarted.<p><li>If<i>action</i>is TCIOFF, the system transmits a STOP character, which isintended to cause the terminal device to stop transmitting datato the system.<p><li>If<i>action</i>is TCION, the system transmits a START character, which isintended to cause the terminal device to start transmitting data tothe system.<p></ul><p>The default on the opening of a terminal file is that neither its inputnor its output are suspended.<p>Attempts to use<i>tcflow()</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 groupto be sent a SIGTTOU signal.If the calling process is blocking or ignoring SIGTTOU signals,the process is allowed to perform the operation, and no signal issent.</blockquote><h4><a name = "tag_000_009_447"> </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_448"> </a>ERRORS</h4><blockquote>The<i>tcflow()</i>function will fail if:<dl compact><dt>[EBADF]<dd>The<i>fildes</i>argument is not a valid file descriptor.<dt>[EINVAL]<dd>The<i>action</i>argument is not a supported value.<dt>[ENOTTY]<dd>The file associated with<i>fildes</i>is not a terminal.</dl><p>The<i>tcflow()</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_449"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_009_450"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_000_009_451"> </a>FUTURE DIRECTIONS</h4><blockquote>In the ISO POSIX-1 standard, the possibility of an [EIO] error occurring is described 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>tcflow()</i>interface definition.It has become clear that this omission was unintended,so it is likely that the [EIO] error will be re-classified asa "will fail" in a future issue of the POSIX standard.</blockquote><h4><a name = "tag_000_009_452"> </a>SEE ALSO</h4><blockquote><i><a href="tcsendbreak.html">tcsendbreak()</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>.<br></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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