Crontab 介绍

一. Crontab 介绍crontab命令的功能是在一定的时间间隔调度一些命令的执行。1.1 /etc/crontab 文件在/etc目录下有一个crontab文件，这里存放有系统运行的一些调度程序。每个用户可以建立自己的调度crontab。如：[root@ www.linuxidc.com~]# cat /etc/crontabSHELL=/bin/bashPATH=/sbin:/bin:/usr/sbin:/usr/binMAILTO=rootHOME=/# run-parts01 * * * * root run-parts /etc/cron.hourly02 4 * * * root run-parts /etc/cron.daily22 4 * * 0 root run-parts /etc/cron.weekly42 4 1 * * root run-parts /etc/cron.monthly1.2 /etc/cron.deny 和 /etc/cron.allow 文件/etc/cron.deny 表示不能使用crontab 命令的用户/etc/cron.allow 表示能使用crontab的用户。如果两个文件同时存在，那么/etc/cron.allow 优先。如果两个文件都不存在，那么只有超级用户可以安排作业。每个用户都会生成一个自己的crontab 文件。这些文件在/var/spool/cron目录下：如：[root@ www.linuxidc.com~]# cd /var/spool/cron[root@ www.linuxidc.comcron]# lsOracle root我们直接查看这个文件，里面的内容和对应用户显示的crontab -l 一致。[root@ www.linuxidc.comcron]# cat oracle00 6 * * * /u02/scripts/del_st_archive.sh >/u02/scripts/del_st_arch.log 2>&1[root@ www.linuxidc.comcron]# cat root0 12 * * * /root/bin/sync-clock.sh[root@ www.linuxidc.comcron]#二. Crontab 使用说明2.1 Crontab语法usage: crontab [-u user] filecrontab [-u user] [ -e | -l | -r ]（default operation is replace, per 1003.2）-e （edit user"s crontab）-l （list user"s crontab）-r （delete user"s crontab）-i （prompt before deleting user"s crontab）-s （selinux context）其中，file是命令文件的名字。如果在命令行中指定了这个文件，那么执行crontab命令，则将这个文件拷贝到crontabs目录下；如果在命令行中没有制定这个文件，crontab命令将接受标准输入（键盘）上键入的命令，并将他们也存放在crontab目录下。帮助：[root@ www.linuxidc.com~]# man crontabCRONTAB（1） CRONTAB（1）NAMEcrontab - maintain crontab files for individual users （ISC Cron V4.1）SYNOPSIScrontab [-u user] filecrontab [-u user] [-l | -r | -e] [-i] [-s]DESCRIPTIONCrontab is the program used to install, deinstall or list the tables used to drive the cron（8） daemon in ISC Cron. Each user can have their own crontab, and though these are files in /var/spool/ , they are not intended to be edited directly. For SELinux in mls mode can be even more crontabs - for each range. For more see selinux（8）.If the cron.allow file exists, then you must be listed therein in order to be allowed to use this command. If the cron.allow file does not exist but the cron.deny file does exist, then you must not be listed in the cron.deny file in order to use this command. If neither of these files exists, only the super user will be allowed to use this command.OPTIONS-u It specifies the name of the user whose crontab is to be tweaked. If this option is not given, crontab examines "your" crontab, i.e., the crontab of the person executing the command. Note that su（8） can confuse crontab and that if you are running inside of su（8） you should always use the -u option for safety¡¯s sake. The first form of this command is used to install a new crontab from some named file or standard input if the pseudo-filename "-" is given.-l The current crontab will be displayed on standard output.-r The current crontab will be be removed.-e This option is used to edit the current crontab using the editor specified by the VISUAL or EDITOR environment variables. After you exit from the edi-tor, the modified crontab will be installed automatically.-i This option modifies the -r option to prompt the user for a ¡¯y/Y¡¯ response before actually removing the crontab.-s It will append the current SELinux security context string as an MLS_LEVEL setting to the crontab file before editing / replacement occurs - see the documentation of MLS_LEVEL in crontab（5）.SEE ALSOcrontab（5）, cron（8）FILES/etc/cron.allow/etc/cron.denySTANDARDSThe crontab command conforms to IEEE Std1003.2-1992 （¡®¡®POSIX¡¯¡¯）. This new command syntax differs from previous versions of Vixie Cron, as well as from the classicSVR3 syntax.DIAGNOSTICSA fairly informative usage message appears if you run it with a bad command line.AUTHORPaul Vixie <vixie@isc.org>4th Berkeley Distribution 16 Januar 2007 CRONTAB（1）

Linux下vmstat 显示结果详解ln 软连接目录相关资讯 Crontab

Linux任务管理工具之 Crontab （08月06日）
Linux定时任务Crontab命令详解（10/24/2015 08:58:49）
CentOS下使用yum命令安装计划任务（10/02/2015 10:04:23）

crontab 问题分析（04月13日）
Ubuntu下用crontab 部署定时任务（10/14/2015 09:17:47）
crontab任务调度健康检测（09/15/2015 10:00:24）

本文评论查看全部评论（0）

评论声明

尊重网上道德，遵守中华人民共和国的各项有关法律法规
承担一切因您的行为而直接或间接导致的民事或刑事法律责任