at定时任务

#at命令是一次性定时任务，执行后不在执行此任务
#默认情况下，atd守护进程每60秒检查作业队列
#检查atd是否后台运行
[root@VM-4-12-centos ~]# ps -ef | grep atd
root      1179     1  0 4月01 ?       00:00:00 /usr/sbin/atd -f
root      3230  2057  0 14:24 pts/0    00:00:00 grep --color=auto atd
#at命令格式
at 【选项】 【时间】
ctrl + D 结束at命令的输入

[root@VM-4-12-centos ~]# at 5pm + 2 days
at> /bin/ls /home<EOT>
job 1 at Tue Apr  4 17:00:00 2023
[root@VM-4-12-centos ~]# at 5pm tomorrow
at> date > /root/date100.log
at> <EOT>
job 2 at Mon Apr  3 17:00:00 2023
[root@VM-4-12-centos ~]# at now + 2 minutes
at> date ?^H^H^H^[[3~<EOT>
job 3 at Sun Apr  2 14:46:00 2023
[root@VM-4-12-centos ~]# atq
1       Tue Apr  4 17:00:00 2023 a root
2       Mon Apr  3 17:00:00 2023 a root
3       Sun Apr  2 14:46:00 2023 a root
[root@VM-4-12-centos ~]# atrm 3
[root@VM-4-12-centos ~]# atq
1       Tue Apr  4 17:00:00 2023 a root
2       Mon Apr  3 17:00:00 2023 a root