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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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<h1>luaposix 36.3</h1>
<ul>
<li><a href="../index.html">Index</a></li>
</ul>
<h2>Examples</h2>
<ul class="nowrap">
<li><a href="../examples/abstract-ns-client.lua.html">abstract-ns-client.lua</a></li>
<li><a href="../examples/abstract-ns-server.lua.html">abstract-ns-server.lua</a></li>
<li><a href="../examples/dir.lua.html">dir.lua</a></li>
<li><strong>dup2.lua</strong></li>
<li><a href="../examples/fork.lua.html">fork.lua</a></li>
<li><a href="../examples/fork2.lua.html">fork2.lua</a></li>
<li><a href="../examples/getopt.lua.html">getopt.lua</a></li>
<li><a href="../examples/glob.lua.html">glob.lua</a></li>
<li><a href="../examples/limit.lua.html">limit.lua</a></li>
<li><a href="../examples/lock.lua.html">lock.lua</a></li>
<li><a href="../examples/netlink-uevent.lua.html">netlink-uevent.lua</a></li>
<li><a href="../examples/packet-socket.lua.html">packet-socket.lua</a></li>
<li><a href="../examples/ping.lua.html">ping.lua</a></li>
<li><a href="../examples/poll.lua.html">poll.lua</a></li>
<li><a href="../examples/rt_sched.lua.html">rt_sched.lua</a></li>
<li><a href="../examples/signal.lua.html">signal.lua</a></li>
<li><a href="../examples/socket.lua.html">socket.lua</a></li>
<li><a href="../examples/termios.lua.html">termios.lua</a></li>
<li><a href="../examples/tree.lua.html">tree.lua</a></li>
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<h2>Modules</h2>
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<li><a href="../modules/posix.html">posix</a></li>
<li><a href="../modules/posix.ctype.html">posix.ctype</a></li>
<li><a href="../modules/posix.dirent.html">posix.dirent</a></li>
<li><a href="../modules/posix.errno.html">posix.errno</a></li>
<li><a href="../modules/posix.fcntl.html">posix.fcntl</a></li>
<li><a href="../modules/posix.fnmatch.html">posix.fnmatch</a></li>
<li><a href="../modules/posix.glob.html">posix.glob</a></li>
<li><a href="../modules/posix.grp.html">posix.grp</a></li>
<li><a href="../modules/posix.libgen.html">posix.libgen</a></li>
<li><a href="../modules/posix.poll.html">posix.poll</a></li>
<li><a href="../modules/posix.pwd.html">posix.pwd</a></li>
<li><a href="../modules/posix.sched.html">posix.sched</a></li>
<li><a href="../modules/posix.signal.html">posix.signal</a></li>
<li><a href="../modules/posix.stdio.html">posix.stdio</a></li>
<li><a href="../modules/posix.stdlib.html">posix.stdlib</a></li>
<li><a href="../modules/posix.sys.msg.html">posix.sys.msg</a></li>
<li><a href="../modules/posix.sys.resource.html">posix.sys.resource</a></li>
<li><a href="../modules/posix.sys.socket.html">posix.sys.socket</a></li>
<li><a href="../modules/posix.sys.stat.html">posix.sys.stat</a></li>
<li><a href="../modules/posix.sys.statvfs.html">posix.sys.statvfs</a></li>
<li><a href="../modules/posix.sys.time.html">posix.sys.time</a></li>
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<li><a href="../modules/posix.sys.wait.html">posix.sys.wait</a></li>
<li><a href="../modules/posix.syslog.html">posix.syslog</a></li>
<li><a href="../modules/posix.termio.html">posix.termio</a></li>
<li><a href="../modules/posix.time.html">posix.time</a></li>
<li><a href="../modules/posix.unistd.html">posix.unistd</a></li>
<li><a href="../modules/posix.utime.html">posix.utime</a></li>
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<h2>dup2.lua</h2>
<pre>
#! /usr/bin/env lua
<span class="keyword">local</span> M = <span class="global">require</span> <span class="string">'posix.unistd'</span>
<span class="keyword">local</span> <span class="keyword">function</span> <span class="function-name">pipe</span>()
<span class="keyword">local</span> r, w = M.<span class="function-name">pipe</span>()
<span class="global">assert</span>(r ~= <span class="keyword">nil</span>, w)
<span class="keyword">return</span> r, w
<span class="keyword">end</span>
<span class="keyword">local</span> stdout_r, stdout_w = <span class="function-name">pipe</span>()
<span class="keyword">local</span> stderr_r, stderr_w = <span class="function-name">pipe</span>()
<span class="keyword">local</span> pid, errmsg = M.<span class="function-name">fork</span>()
<span class="global">assert</span>(pid ~= <span class="keyword">nil</span>, errmsg)
<span class="keyword">if</span> pid == <span class="number">0</span> <span class="keyword">then</span>
<span class="comment">-- Child Process:
</span>
M.<span class="function-name">close</span>(stdout_r)
M.<span class="function-name">close</span>(stderr_r)
M.<span class="function-name">dup2</span>(stdout_w, M.STDOUT_FILENO)
M.<span class="function-name">dup2</span>(stderr_w, M.STDERR_FILENO)
<span class="comment">-- Exec() a subprocess here instead if you like --
</span>
<span class="global">io</span>.stdout:<span class="function-name">write</span> <span class="string">'output string'</span>
<span class="global">io</span>.stderr:<span class="function-name">write</span> <span class="string">'oh noes!'</span>
<span class="global">os</span>.<span class="function-name">exit</span>(<span class="number">42</span>)
<span class="keyword">else</span>
<span class="comment">-- Parent Process:
</span>
M.<span class="function-name">close</span>(stdout_w)
M.<span class="function-name">close</span>(stderr_w)
<span class="keyword">local</span> <span class="keyword">function</span> <span class="function-name">read</span>(msg, fd)
<span class="keyword">local</span> outs, errmsg = M.<span class="function-name">read</span>(fd, <span class="number">1024</span>)
<span class="global">assert</span>(outs ~= <span class="keyword">nil</span>, errmsg)
<span class="global">print</span>(msg, outs)
<span class="keyword">end</span>
<span class="function-name">read</span>(<span class="string">'STDOUT:'</span>, stdout_r)
<span class="function-name">read</span>(<span class="string">'STDERR:'</span>, stderr_r)
<span class="keyword">local</span> childpid, reason, status = <span class="global">require</span> <span class="string">'posix.sys.wait'</span>.<span class="function-name">wait</span>(pid)
<span class="global">assert</span>(childpid ~= <span class="keyword">nil</span>, reason)
<span class="global">print</span>(<span class="string">'child '</span> .. reason, status)
<span class="keyword">end</span></pre>
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