121 lines
4.0 KiB
HTML
121 lines
4.0 KiB
HTML
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-->
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<html>
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<head>
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<title>pipe</title>
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<link rel="stylesheet" type="text/css" media="all" href="../man.css">
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</head>
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<body bgcolor=#ffffff>
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<h2 align=center>pipe</h2>
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<h4 align=center>OS/161 Reference Manual</h4>
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<h3>Name</h3>
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<p>
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pipe - create pipe object
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</p>
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<h3>Library</h3>
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<p>
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Standard C Library (libc, -lc)
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</p>
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<h3>Synopsis</h3>
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<p>
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<tt>#include <unistd.h></tt><br>
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<br>
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<tt>int</tt><br>
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<tt>pipe(int *</tt><em>fds</em><tt>);</tt>
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</p>
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<h3>Description</h3>
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<p>
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The <tt>pipe</tt> call creates an anonymous pipe object in the system,
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and binds it to two file handles in the current process, one for the
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read end and one for the write end. (Pipes are unidirectional.)
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</p>
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<p>
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Data written on the write end may be read from the read end. Once all
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references to the write end are closed, and all remaining data is
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read, further reads return EOF. If all references to the read end are
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closed before the write end is closed, further writes generate EPIPE.
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The pipe object itself is destroyed when all references to both ends
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are closed.
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</p>
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<p>
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<em>fds</em> is a pointer to space for two integers. A file handle for
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the read end of the pipe is stored in <em>fds</em>[0], and a file
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handle for the write end is stored in <em>fds</em>[1].
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</p>
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<p>
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<tt>pipe</tt> is most often used in conjunction with <A
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HREF=dup2.html>dup2</A> and <A HREF=fork.html>fork</A> to send the
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standard output of one process to the standard input of another.
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</p>
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<p>
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In POSIX, pipe I/O of data blocks smaller than a standard constant
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PIPE_BUF is guaranteed to be atomic. If you implement pipes, you need
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not necessarily implement POSIX semantics, but you should decide what
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sort of atomicity guarantees you wish to make and specify them
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carefully.
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</p>
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<h3>Return Values</h3>
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<p>
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On success, pipe returns 0. On error, -1 is returned, and
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<A HREF=errno.html>errno</A> is set according to the error
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encountered.
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</p>
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<h3>Errors</h3>
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<p>
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The following error codes should be returned under the conditions
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given. Other error codes may be returned for other cases not
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mentioned here.
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<table width=90%>
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<tr><td width=5% rowspan=3> </td>
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<td width=10% valign=top>EMFILE</td>
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<td>The process's file table was full, or a
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process-specific limit on open files
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was reached.</td></tr>
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<tr><td valign=top>ENFILE</td> <td>The system file table is full, if such a
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thing exists, or a system-wide limit
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on open files was reached.</td></tr>
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<tr><td valign=top>EFAULT</td> <td><em>fds</em> was an invalid
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pointer.</td></tr>
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</table>
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</p>
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</body>
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</html>
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