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<head>
<title>pipe(3) - Plan 9 from User Space</title>
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<tr><td width=20><td><b>PIPE(3)</b><td align=right><b>PIPE(3)</b>
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<p><font size=+1><b>NAME </b></font><br>
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pipe &ndash; create an interprocess channel<br>
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<p><font size=+1><b>SYNOPSIS </b></font><br>
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<tt><font size=+1>#include &lt;u.h&gt;<br>
#include &lt;libc.h&gt;
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<tt><font size=+1>int pipe(int fd[2])<br>
</font></tt>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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<i>Pipe</i> creates a buffered channel for interprocess I/O communication.
Two file descriptors are returned in <i>fd</i>. Data written to <tt><font size=+1>fd[1]</font></tt>
is available for reading from <tt><font size=+1>fd[0]</font></tt> and data written to <tt><font size=+1>fd[0]</font></tt>
is available for reading from <tt><font size=+1>fd[1]</font></tt>.
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After the pipe has been established, cooperating processes created
by subsequent <a href="../man2/fork.html"><i>fork</i>(2)</a> calls may pass data through the pipe with
<i>read</i> and <i>write</i> calls.
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When all the data has been read from a pipe and the writer has
closed the pipe or exited, <a href="../man3/read.html"><i>read</i>(3)</a> will return 0 bytes. Writes
to a pipe with no reader will generate a note <tt><font size=+1>sys: write on closed
pipe</font></tt>.<br>
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<p><font size=+1><b>SOURCE </b></font><br>
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<tt><font size=+1>/usr/local/plan9/src/lib9/pipe.c<br>
</font></tt>
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<p><font size=+1><b>SEE ALSO </b></font><br>
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<a href="../man3/intro.html"><i>intro</i>(3)</a>, <a href="../man3/read.html"><i>read</i>(3)</a><br>
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<p><font size=+1><b>DIAGNOSTICS </b></font><br>
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Sets <i>errstr</i>.<br>
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<p><font size=+1><b>BUGS </b></font><br>
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If a read or a write of a pipe is interrupted, some unknown number
of bytes may have been transferred.
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<i>Pipe</i> is a macro defined as <i>p9pipe</i> to avoid name conflicts with
Unix&#8217;s <i>pipe</i> system call.
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Unix pipes are not guaranteed to be bidirectional. In order to
ensure a bidirectional channel, <i>p9pipe</i> creates Unix domain sockets
via the <a href="../man2/socketpair.html"><i>socketpair</i>(2)</a> instead of Unix pipes.
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The implementation of pipes as Unix domain sockets causes problems
with some Unix implementations of <tt><font size=+1>/dev/fd</font></tt>, Unix&#8217;s dup device.
If a Unix domain socket is open as file descriptor 0, some implementations
disallow the opening of <tt><font size=+1>/dev/fd/0</font></tt>; instead one must <a href="../man2/connect.html"><i>connect</i>(2)</a>
to it. If this functionality is important
(as it is for <a href="../man1/rc.html"><i>rc</i>(1)</a>), one must <tt><font size=+1>#undef pipe</font></tt> and fall back on the
(possibly unidirectional) Unix pipes.<br>
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