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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>10.5. Daemon</title><link rel="stylesheet" type="text/css" href="..//docbook.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><meta name="keywords" content="php, pear, pecl, phar" /><link rel="home" href="../index.html" title="Netkiller Python 手札" /><link rel="up" href="index.html" title="第 10 章 Library" /><link rel="prev" href="ch10s04.html" title="10.4. Socket" /><link rel="next" href="python-memcached.html" title="10.6. python-memcached" /></head><body><a xmlns="" href="//www.netkiller.cn/">Home</a> |
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<a xmlns="" href="mailto:netkiller@msn.com">Email</a><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">10.5. Daemon</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch10s04.html">上一页</a> </td><th width="60%" align="center">第 10 章 Library</th><td width="20%" align="right"> <a accesskey="n" href="python-memcached.html">下一页</a></td></tr></table><hr /></div><table xmlns=""><tr><td><iframe src="//ghbtns.com/github-btn.html?user=netkiller&repo=netkiller.github.io&type=watch&count=true&size=large" height="30" width="170" frameborder="0" scrolling="0" style="width:170px; height: 30px;" allowTransparency="true"></iframe></td><td><iframe src="//ghbtns.com/github-btn.html?user=netkiller&repo=netkiller.github.io&type=fork&count=true&size=large" height="30" width="170" frameborder="0" scrolling="0" style="width:170px; height: 30px;" allowTransparency="true"></iframe></td><td><iframe src="//ghbtns.com/github-btn.html?user=netkiller&type=follow&count=true&size=large" height="30" width="240" frameborder="0" scrolling="0" style="width:240px; height: 30px;" allowTransparency="true"></iframe></td></tr></table><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="daemon"></a>10.5. Daemon</h2></div></div></div>
<p>http://www.myelin.co.nz/post/2003/3/13/#200303135</p>
<pre class="programlisting">
#!/usr/bin/env python
import os, sys
print "I'm going to fork now - the child will write something to a pipe, and the parent will read it back"
r, w = os.pipe() # r,w是文件描述符, 不是文件对象
pid = os.fork()
if pid:
# 父进程
os.close(w) # 关闭一个文件描述符
r = os.fdopen(r) # 将r转化为文件对象
print "parent: reading"
txt = r.read()
os.waitpid(pid, 0) # 确保子进程被撤销
else:
# 子进程
os.close(r)
w = os.fdopen(w, 'w')
print "child: writing"
w.write("here's some text from the child")
w.close()
print "child: closing"
sys.exit(0)
print "parent: got it; text =", txt
</pre>
<pre class="programlisting">
import sys, os
if __name__ == "__main__":
# do the UNIX double-fork magic, see Stevens' "Advanced
# Programming in the UNIX Environment" for details (ISBN 0201563177)
try:
pid = os.fork()
if pid > 0:
# exit first parent
sys.exit(0)
except OSError, e:
print >>sys.stderr, "fork #1 failed: %d (%s)" % (e.errno, e.strerror)
sys.exit(1)
# decouple from parent environment
os.chdir("/")
os.setsid()
os.umask(0)
# do second fork
try:
pid = os.fork()
if pid > 0:
# exit from second parent, print eventual PID before
print "Daemon PID %d" % pid
sys.exit(0)
except OSError, e:
print >>sys.stderr, "fork #2 failed: %d (%s)" % (e.errno, e.strerror)
sys.exit(1)
# start the daemon main loop
</pre>
<p></p>
<pre class="programlisting">
# Redirect standard file descriptors
sys.stdin = open('/dev/null', 'r')
sys.stdout = open('/dev/null', 'w')
sys.stderr = open('/dev/null', 'w')
</pre>
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