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<h1>luaposix 36.3</h1>
<ul>
<li><a href="../index.html">Index</a></li>
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<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><a href="../examples/dup2.lua.html">dup2.lua</a></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><strong>lock.lua</strong></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>
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<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>
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<li><a href="../modules/posix.unistd.html">posix.unistd</a></li>
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<h2>lock.lua</h2>
<pre>
#! /usr/bin/env lua
<span class="keyword">local</span> M = <span class="global">require</span> <span class="string">'posix.fcntl'</span>
<span class="keyword">local</span> S = <span class="global">require</span> <span class="string">'posix.sys.stat'</span>
<span class="keyword">local</span> fd = M.<span class="function-name">open</span>(
<span class="string">'file.txt'</span>,
M.O_CREAT + M.O_WRONLY + M.O_TRUNC,
S.S_IRUSR + S.S_IWUSR + S.S_IRGRP + S.S_IROTH
)
<span class="comment">-- Set lock on file
</span><span class="keyword">local</span> lock = {
l_type = M.F_WRLCK; <span class="comment">-- Exclusive lock
</span> l_whence = M.SEEK_SET; <span class="comment">-- Relative to beginning of file
</span> l_start = <span class="number">0</span>; <span class="comment">-- Start from 1st byte
</span> l_len = <span class="number">0</span>; <span class="comment">-- Lock whole file
</span>}
<span class="keyword">if</span> M.<span class="function-name">fcntl</span>(fd, M.F_SETLK, lock) == -<span class="number">1</span> <span class="keyword">then</span>
<span class="global">error</span>(<span class="string">'file locked by another process'</span>)
<span class="keyword">end</span>
<span class="comment">-- Do something with file while it's locked
</span><span class="global">require</span> <span class="string">'posix.unistd'</span>.<span class="function-name">write</span>(fd, <span class="string">'Lorem ipsum\n'</span>)
<span class="comment">-- Release the lock
</span>lock.l_type = M.F_UNLCK
M.<span class="function-name">fcntl</span>(fd, M.F_SETLK, lock)</pre>
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