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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 – 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 <u.h><br> |
| #include <libc.h> |
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| </font></tt> |
| <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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| </table> |
| <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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| </table> |
| <p><font size=+1><b>DIAGNOSTICS </b></font><br> |
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| Sets <i>errstr</i>.<br> |
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| </table> |
| <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’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’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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