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  • linux后台执行命令crontab

    有如下几种方式:
    crontab
    at
    &
    nohup

    1. crontab
    定时执行任务

    # crontab -e    //编辑crontab配置文件
    
    Select an editor.  To change later, run 'select-editor'.
      1. /bin/ed
      2. /bin/nano        <---- easiest
      3. /usr/bin/emacs24
      4. /usr/bin/vim.basic
      5. /usr/bin/vim.tiny
    
    Choose 1-5 [2]: 
    # crontab  -l   //查看crontab配置文件
    
    # Edit this file to introduce tasks to be run by cron.
    # 
    # Each task to run has to be defined through a single line
    # indicating with different fields when the task will be run
    # and what command to run for the task
    # 
    # To define the time you can provide concrete values for
    # minute (m), hour (h), day of month (dom), month (mon),
    # and day of week (dow) or use '*' in these fields (for 'any').# 
    # Notice that tasks will be started based on the cron's system
    # daemon's notion of time and timezones.
    # 
    # Output of the crontab jobs (including errors) is sent through
    # email to the user the crontab file belongs to (unless redirected).
    # 
    # For example, you can run a backup of all your user accounts
    # at 5 a.m every week with:
    # 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
    # 
    # For more information see the manual pages of crontab(5) and cron(8)
    # 
    # m h  dom mon dow   command
    5       *       *           *     *     ls 
    # crontab  -r   //删除所有调度任务

    语法格式

    小时 星期 命令
    0-59 0-23 1-31 1-12 0-6 cmd

    特殊符号

    *:所有数字
    /:每
    -:一个区间
    ,:多个数字

    2. at
    特定任务运行一次

    # service atd status    //查看atd服务
    atd start/running, process 1350
    # at now + 5 minutes    //添加
    warning: commands will be executed using /bin/sh
    at> /home/a.out
    at> ctrl+D
    job 4 at Wed Apr 19 14:48:00 2017
    时间 例子 说明
    Minute at now + 5 minutes 任务在5分钟后运行
    Hour at now + 1 hour 任务在1小时后运行
    Days at now + 3 days 任务在3天后运行
    Weeks at now + 2 weeks 任务在两周后运行
    Fixed at midnight 任务在午夜运行
    Fixed at 10:30pm 任务在晚上10点30分
    Fixed at 23:59 12/31/2018 任务在2018年12月31号23点59分
    # at -l //列出所有作业
    1       Thu Apr 20 02:05:00 2017 a thomas
    # at -r job //删除作业
    Warning: deleting running job

    3. &
    在后台运行一个占用时间不长的任务

    # jobs  //查看后台运行任务
    # fg    //将后台运行任务调至前台

    4. ctrl + z
    将一个正在前台执行的命令放到后台,并且处于暂停状态

    5. nohup
    在后台运行一个命令,即使在用户退出时也不受影响

    # nohup --help
    Usage: nohup COMMAND [ARG]...
      or:  nohup OPTION

    6. 查看当前终端的进程id

    # echo $$ 
    2602
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  • 原文地址:https://www.cnblogs.com/zhangxuechao/p/11709734.html
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