Linux中crontab定时任务不执行的原因
<p>最近在linux中遇到了个crontab定时任务不执行的case,在这给大家分享一下，避免踩到我遇到的坑。</p>
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先贴脚本吧</p>
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为了方便展示，把脚本入参，都写死了</p>
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<code class="bash preprocessor bold">#!/usr/bin/env bash</code>
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<code class="bash comments"># 1输出文件，到log 例如： bg </code>
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<code class="bash comments"># 2 目标文件目录 不带最后的/ 例如：/opt/flume/home/hdp_lbg_ectech/rawdata/xxx/web_vip_bg</code>
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<code class="bash comments"># 3 执行的时候选择前几天的日志 例如：１</code>
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<code class="bash plain">LAST_DAY=$(</code><code class="bash functions">date</code> <code class="bash plain">+</code><code class="bash string">"%Y-%m-%d"</code> <code class="bash plain">-d </code><code class="bash string">"1 days ago"</code><code class="bash plain">)</code>
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<code class="bash plain">LAST_HOUR_DAY=$(</code><code class="bash functions">date</code> <code class="bash plain">+</code><code class="bash string">"%Y%m%d"</code> <code class="bash plain">-d </code><code class="bash string">"1 days ago"</code><code class="bash plain">)</code>
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<code class="bash comments">#执行jar获取bg日志</code>
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<code class="bash spaces"> </code><code class="bash plain">java -jar </code><code class="bash plain">/opt/script/xxx/vipbg/vip-bg-job-1</code><code class="bash plain">.0-SNAPSHOT-shaded.jar </code><code class="bash plain">/opt/script/xxx/vipbg/bg</code><code class="bash plain">.log</code>
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<code class="bash comments">#具体到文件名</code>
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<code class="bash plain">SRC_FILE=</code><code class="bash plain">/opt/script/xxx/vipbg/bg</code><code class="bash plain">.log</code>
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<code class="bash comments">#指定目标目录,按日期创建目录</code>
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<code class="bash plain">DEST_DIR_NAME=</code><code class="bash plain">/opt/flume/home/hdp_lbg_ectech/rawdata/xxx/web_vip_bg/</code><code class="bash plain">$LAST_HOUR_DAY</code>
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<code class="bash plain">DEST_FILE_NAME=$(</code><code class="bash functions">basename</code> <code class="bash plain">$SRC_FILE)</code>
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<code class="bash comments">#FLUME会忽略隐藏文件，所以可直接拷贝过去</code>
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<code class="bash plain">TMP_FILE=$DEST_DIR_NAME/.$DEST_FILE_NAME</code>
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<code class="bash plain">DEST_FILE=$DEST_DIR_NAME/$DEST_FILE_NAME.$SRC_IP</code>
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<code class="bash comments">#判断源文件是否非空,空文件Flume会直接删除的,且目标文件不存在,避免重复拷贝数据</code>
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<code class="bash keyword">if</code> <code class="bash plain">[ -s </code><code class="bash string">"$SRC_FILE"</code> <code class="bash plain">] && [ ! -f </code><code class="bash string">"$DEST_FILE"</code> <code class="bash plain">];</code><code class="bash keyword">then</code>
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<code class="bash spaces"> </code><code class="bash comments">#使Flume具有删除该目录下文件的权限,不然FLUME收集不上去</code>
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<code class="bash spaces"> </code><code class="bash functions">mkdir</code> <code class="bash plain">-p $DEST_DIR_NAME && </code><code class="bash functions">chmod</code> <code class="bash plain">777 $DEST_DIR_NAME</code>
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<code class="bash spaces"> </code><code class="bash comments">#必须先cp到一个临时文件再mv过去,直接cp过去会造成数据丢失</code>
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<code class="bash spaces"> </code><code class="bash functions">cp</code> <code class="bash plain">$SRC_FILE $TMP_FILE && </code><code class="bash functions">mv</code> <code class="bash plain">$TMP_FILE $DEST_FILE</code>
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<code class="bash keyword">fi</code>
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<code class="bash comments">#删除tmp中转文件</code>
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<code class="bash functions">rm</code> <code class="bash plain">-rf </code><code class="bash plain">/opt/script/xxx/vipbg/bg</code><code class="bash plain">.log</code>
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<code class="bash functions">echo</code> <code class="bash string">"删除源文件成功"</code>
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<p>
有些目录用了xxx代表</p>
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这个脚本单独考出来可以执行，放到crontab里面就不执行了， 百度了下，大多都说需要使用绝对路径，看了下我们的脚本，就是下面这句有问题：</p>
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<span><u>复制代码</u></span> 代码如下:</div>
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java -jar /opt/script/xxx/vipbg/vip-bg-job-1.0-SNAPSHOT-shaded.jar /opt/script/xxx/vipbg/bg.log</div>
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初步判断是java这需要使用jdk的目录路径，做了两个实验测试了下。</p>
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<strong>crontab中加上一个 java -jar xxxx.jar的定时任务</strong></p>
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代码如下：</p>
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<span><u>复制代码</u></span> 代码如下:</div>
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10 16 * * * java -jar /opt/script/xxx/vipbg/vip-bg-job-1.0-SNAPSHOT-shaded.jar /opt/script/xxx/vipbg/bg.log</div>
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果然，这个没有执行</p>
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<strong>crontab中加上一个 jdk目录/bin/java -jar xxxx.jar的定时任务</strong></p>
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代码如下：</p>
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<span><u>复制代码</u></span> 代码如下:</div>
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20 16 * * * /opt/soft/jdk/jdk1.6.0_45/bin/java -jar /opt/script/xxx/vipbg/vip-bg-job-1.0-SNAPSHOT-shaded.jar /opt/script/xxx/vipbg/bg.log</div>
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这次执行了，没有执行的原因就是执行jar的时候，需要加上jdk的路径</p>
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以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。</p>
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原文链接：https://www.jianshu.com/p/20fd3fa063b1</p>
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