crontab scheduled task configuration record
/etc/crontab 文件 这是系统运行的调度任务 /var/spool/cron 目录 用户自定义的crontab任务放在此目录下 ls –lrt /etc/cron* /etc/cron.deny 表示不能使用crontab命令的用户 /etc/cron.allow 表示能使用crontab命令的用户 默认情况下,cron.allow不存在,如果都存在,cron.allow优先
具体可 crontab --help 或者 man crontab|more crontab –l //查看当前用户的定时任务 crontab –e //编辑当前用户的定时任务 crontab –r //删除当前用户的定时任务
59 23 * * * /home/xxx/crontab/test.sh > /dev/null 2>&1 & 前6列暂且用C1 - C6表示 C1 分 (1-59) C2 时 (1-23,0表示子夜) C3 日 (1-31) C4 月 (1-12) C5 星期 (0-6,0表示星期天,1表示星期一,以此类推) C6 要运行的命令 前5列表示 命令执行的频率,最小频率是每分钟一次,其中Cn的值可用四种形式表示: * , */n , T1-T2 , a,b,c 当C1 为 * 时,表示每分钟都要执行命令 当C1 为 */n时,表示每隔n分钟执行一次命令 当C1 为 T1-T2时,表示从 T1分钟 到 T2分钟时间内都要执行命令 当C1 为 a,b,c 时,表示第 a,b,c 分钟都要执行命令 示例调用: 12 12 * * * /home/xxx/crontab/test.sh >/dev/null 2>&1 表示每天的12点12分 执行脚本 */2 * * * * /home/xxx/crontab/test.sh >/dev/null 2>&1 表示每隔2分钟 执行一次脚本 0 23 * * 1-5 /home/xxx/crontab/test.sh >/dev/null 2>&1 表示每周一到周五的23点 执行一次脚本 0 19 * * 0 mail -s "xxx" xxx@mail.com < /tmp/maildata 表示每周日的19点 发送邮件到 xxx@mail.com
关于命令中 /dev/null 2>&1 的解释 0 表示键盘输入 1 表示标准输出 2 表示错误输出 1.创建test.sh,内容如下 #! /bin/bash echo "time is " `date` 2.添加定时任务 * * * * * /home/xxx/crontab/test.sh > /home/xxx/crontab/test.log & 默认是1,和下面方法一致 * * * * * /home/xxx/crontab/test.sh 1> /home/xxx/crontab/test.log & * * * * * /home/xxx/crontab/test.sh > /home/xxx/crontab/test.log 2>&1 & 3.说明 1代表,标准输出,所以上述命令会将脚本的输出结果,输出到后面指定的log文件中,而不是打印到屏幕; 2代表,错误输出,&1表示文件的描述,这里表示脚本执行的错误信息重定向到1(标准输出) 而1已经重定向到指定的log文件中,所以信息都会输出到log文件 不能写成 2>1 ,缺少&,会认为是错误信息输出到名称为 1 文件中
1.shell中需设置必要的环境变量 crontab的环境变量默认不包含系统当前用户的环境,所以需添加必要的环境变量 2.尽量采用完整路径方法,避免使用相对路径 3.避免脚本的重复执行 if(exec("ps -ef |grep 'php'|grep 'updateScript'|grep -v 'grep' |wc -l ") > 2){ die(); } grep -v 'grep' 表示结果去过滤掉 grep 那一行 wc -l 表示统计满足条件的行数 这样就可以判断 php进程中,名为 updateScript 的脚本 是否已经执行了
http://www.cnblogs.com/kerrycode/p/3238346.html http://www.cnblogs.com/hazir/p/sudo_command.html
The above introduces the crontab scheduled task configuration record, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.

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