113 lines
3.5 KiB
HTML
113 lines
3.5 KiB
HTML
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-->
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<html>
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<head>
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<title>fork</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>fork</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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fork - copy the current process
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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>pid_t</tt><br>
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<tt>fork(void);</tt>
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</p>
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<h3>Description</h3>
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<p>
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<tt>fork</tt> duplicates the currently running process. The two copies
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are identical, except that one (the "new" one, or "child"), has a new,
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unique process id, and in the other (the "parent") the process id is
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unchanged.
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</p>
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<p>
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The process id must be greater than 0.
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</p>
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<p>
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The two processes do not share memory or open file tables; this state
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is copied into the new process, and subsequent modification in one
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process does not affect the other.
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</p>
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<p>
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However, the file handle objects the file tables point to are shared,
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so, for instance, calls to lseek in one process can affect the other.
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</p>
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<h3>Return Values</h3>
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<p>
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On success, <tt>fork</tt> returns twice, once in the parent process
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and once in the child process. In the child process, 0 is returned. In
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the parent process, the process id of the new child process is
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returned.
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</p>
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<p>
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On error, no new process is created. <tt>fork,</tt> only returns once,
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returning -1, and <A HREF=errno.html>errno</A> is set according to the
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error 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 errors 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>EMPROC</td>
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<td>The current user already has too
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many processes.</td></tr>
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<tr><td valign=top>ENPROC</td> <td>There are already too many
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processes on the system.</td></tr>
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<tr><td valign=top>ENOMEM</td> <td>Sufficient virtual memory for the new
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process was not available.</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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