Centos 7下利用crontab定时执行任务详解
<p><span><strong>前言</strong></span></p>
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cron服务是Linux的内置服务，但它不会开机自动启动。可以用以下命令启动和停止服务：</p>
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<code class="bash plain">/sbin/service</code> <code class="bash plain">crond start</code>
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<code class="bash plain">/sbin/service</code> <code class="bash plain">crond stop</code>
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<code class="bash plain">/sbin/service</code> <code class="bash plain">crond restart</code>
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<code class="bash plain">/sbin/service</code> <code class="bash plain">crond reload</code>
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以上1-4行分别为启动、停止、重启服务和重新加载配置。</p>
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要把cron设为在开机的时候自动启动，在 /etc/rc.d/rc.local 脚本中加入 /sbin/service crond start 即可</p>
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查看当前用户的crontab，输入 <code>crontab -l</code>；</p>
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编辑crontab，输入 <code>crontab -e</code>；</p>
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删除crontab，输入 <code>crontab -r</code></p>
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<span><strong>添加任务</strong></span></p>
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<code class="bash functions">crontab</code> <code class="bash plain">-e</code>
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<code class="bash plain">0 *</code><code class="bash plain">/1</code> <code class="bash plain">* * * </code><code class="bash functions">command</code>
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<code class="bash plain">0 *</code><code class="bash plain">/2</code> <code class="bash plain">* * * </code><code class="bash functions">command</code>
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查询任务是否加了：</p>
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<code class="bash functions">crontab</code> <code class="bash plain">-l -u root </code><code class="bash comments">#查看root用户</code>
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<code class="bash plain">0 *</code><code class="bash plain">/1</code> <code class="bash plain">* * * </code><code class="bash functions">command</code>
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<code class="bash plain">0 *</code><code class="bash plain">/2</code> <code class="bash plain">* * * </code><code class="bash functions">command</code>
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<span><strong>基本格式 :</strong></span></p>
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* * * * * command</p>
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分 时 日 月 周 命令</p>
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第1列表示分钟1～59 每分钟用*或者 */1表示</p>
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第2列表示小时1～23（0表示0点）</p>
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第3列表示日期1～31</p>
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第4列表示月份1～12</p>
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第5列标识号星期0～6（0表示星期天）</p>
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第6列要运行的命令</p>
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<span><strong>crontab文件的一些例子：</strong></span></p>
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<code class="bash plain">30 21 * * * </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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上面的例子表示每晚的21:30重启apache。</p>
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<code class="bash plain">45 4 1,10,22 * * </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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上面的例子表示每月1、10、22日的4 : 45重启apache。</p>
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<code class="bash plain">10 1 * * 6,0 </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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上面的例子表示每周六、周日的1 : 10重启apache。</p>
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<code class="bash plain">0,30 18-23 * * * </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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上面的例子表示在每天18 : 00至23 : 00之间每隔30分钟重启apache。</p>
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<code class="bash plain">0 23 * * 6 </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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上面的例子表示每星期六的11 : 00 pm重启apache。</p>
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<code class="bash plain">* *</code><code class="bash plain">/1</code> <code class="bash plain">* * * </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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每一小时重启apache</p>
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<code class="bash plain">* 23-7</code><code class="bash plain">/1</code> <code class="bash plain">* * * </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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晚上11点到早上7点之间，每隔一小时重启apache</p>
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<code class="bash plain">0 11 4 * mon-wed </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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每月的4号与每周一到周三的11点重启apache</p>
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<code class="bash plain">0 4 1 jan * </code><code class="bash plain">/usr/local/etc/rc</code><code class="bash plain">.d</code><code class="bash plain">/lighttpd</code> <code class="bash plain">restart</code>
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一月一号的4点重启apache</p>
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<span><strong>总结</strong></span></p>
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以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流，谢谢大家对服务器之家的支持。</p>
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原文链接：http://www.cnblogs.com/jianqingwang/p/6726589.html</p>
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