选择编辑定时任务时使用的编辑器
$ select-editor
Select an editor. To change later, run 'select-editor'.
1. /bin/ed
2. /bin/nano <---- easiest
3. /usr/bin/code
4. /usr/bin/vim.basic
5. /usr/bin/vim.tiny
Choose 1-5 [2]: 4
编辑定时任务
编辑当前用户的定时任务
crontab -e
如果当前用户为 huangjian，crontab -u huangjian -e 和 crontab -e 是一样的。
sudo crontab -u root -e 编辑 root 用户的定时任务
编辑好之后，保存了，就生效了。如果要删除某个定时任务，也用 crontab -e 这个
命令打开 crontab 文件，删除掉了，再保存了就好了。
查看定时任务
$ crontab -l
*/1 * * * * /home/huangjian/local/BashUtils/nginx/rotate.sh
删除掉所有的定时任务
这个命令慎用！！！
crontab -r 删除掉当前用户的所有定时任务
sudo crontab -u root -r 删除掉 root 用户的所有定时任务
cron expression
| Field name | Allowed values | Allowed special characters |
|---|---|---|
| Minutes | 0-59 | * / , - |
| Hours | 0-23 | * / , - |
| Day of month | 1-31 | * / , - ? |
| Month | 1-12 or JAN-DEC | * / , - |
| Day of week | 0-6 or SUN-SAT | * / , - ? |
例子
# Field name | Allowed values | Allowed special characters
# ---------- | -------------- | --------------------------
# Minutes | 0-59 | * / , -
# Hours | 0-23 | * / , -
# Day of month | 1-31 | * / , - ?
# Month | 1-12 or JAN-DEC | * / , -
# Day of week | 0-6 or SUN-SAT | * / , - ?
#
# * 表示匹配所有的值。
# 比如说 Minutes 使用 * 表示每分钟。
# Hours 使用 * 表示每小时。
# Month 使用 * 表示每个月。
#
# / 表示范围和间隔。
# Minutes 使用 3-59/15 表示从第 3 分钟到第 59 分钟，每隔 15 分钟。
# 每天的 0 点，1 点，2 点....时执行命令
0 0 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_24_00.txt
0 1 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_01_00.txt
0 2 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_02_00.txt
0 3 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_03_00.txt
0 4 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_04_00.txt
0 5 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_05_00.txt
0 6 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_06_00.txt
0 7 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_07_00.txt
0 8 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_08_00.txt
0 9 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_09_00.txt
0 10 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_10_00.txt
0 11 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_11_00.txt
0 12 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_12_00.txt
0 13 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_13_00.txt
0 14 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_14_00.txt
0 15 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_15_00.txt
0 16 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_16_00.txt
0 17 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_17_00.txt
0 18 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_18_00.txt
0 19 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_19_00.txt
0 20 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_20_00.txt
0 21 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_21_00.txt
0 22 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_22_00.txt
0 23 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_23_00.txt
# 每天的 7:50 执行命令
50 7 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_07_50.txt
# 每天的 22:50 执行命令
50 22 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_22_50.txt
# 每隔 1 分钟，2 分钟，3 分钟，4 分钟执行命令
*/1 * * * * echo `date` >> /home/huangjian/crontab_demo/every_1_minute.txt
*/2 * * * * echo `date` >> /home/huangjian/crontab_demo/every_2_minute.txt
*/3 * * * * echo `date` >> /home/huangjian/crontab_demo/every_3_minute.txt
*/4 * * * * echo `date` >> /home/huangjian/crontab_demo/every_4_minute.txt
*/5 * * * * echo `date` >> /home/huangjian/crontab_demo/every_5_minute.txt
*/6 * * * * echo `date` >> /home/huangjian/crontab_demo/every_6_minute.txt
*/7 * * * * echo `date` >> /home/huangjian/crontab_demo/every_7_minute.txt
# 每隔 1 分钟执行一次命令
* * * * * echo `date` >> /home/huangjian/crontab_demo/every_1_minute_method1.txt
# 每隔 1 小时，2 小时，3 小时，4 小时，5 小时，6 小时，7 小时执行命令
0 */1 * * * echo `date` >> /home/huangjian/crontab_demo/every_1_hours.txt
0 */2 * * * echo `date` >> /home/huangjian/crontab_demo/every_2_hours.txt
0 */3 * * * echo `date` >> /home/huangjian/crontab_demo/every_3_hours.txt
0 */4 * * * echo `date` >> /home/huangjian/crontab_demo/every_4_hours.txt
0 */5 * * * echo `date` >> /home/huangjian/crontab_demo/every_5_hours.txt
0 */6 * * * echo `date` >> /home/huangjian/crontab_demo/every_6_hours.txt
0 */7 * * * echo `date` >> /home/huangjian/crontab_demo/every_7_hours.txt
# 每小时的第 0 分钟，第 1 分钟，第 2 分钟，第 3 分钟，.... 执行命令
0 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_0th.txt
1 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_1th.txt
2 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_2th.txt
3 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_3th.txt
4 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_4th.txt
5 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_5th.txt
6 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_6th.txt
7 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_7th.txt
# 每天的 6 点到 12 点之间，每隔 3 小时执行命令
0 6-12/3 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_6-12_hour_every_3_hour.txt
# 每天的 7 点到 12 点之间，每隔 3 小时执行命令
0 7-12/3 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_7-12_hour_every_3_hour.txt
# 每天的 0 点 20 分，2 点 20 分，4 点 20 分，.... 执行命令
20 0-23/2 * * * echo `date` >> /home/huangjian/crontab_demo/every_2_hour_20th_minute.txt
# 每月的 1 号，2 号，3 号，4 号，5 号，6 号，7 号执行命令
0 0 1 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_1.txt
0 0 2 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_2.txt
0 0 3 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_3.txt
0 0 4 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_4.txt
0 0 5 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_5.txt
0 0 6 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_6.txt
0 0 7 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_7.txt
# 每月的 1 号和 15 号执行命令
0 0 1,15 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_1_and_15.txt
# 每周的的周一到周五的 3 点钟执行命令
0 3 * * 1-5 echo `date` >> /home/huangjian/crontab_demo/week_1-5_everyday_3th_hour.txt
# 在周六和周天的 00:00 执行命令
0 0 * * 0,6 echo `date` >> /home/huangjian/crontab_demo/week_6-7_00_00.txt
# 在每个月的 1、11、21、31 号，的 6:30 分执行命令
30 6 */10 * * echo `date` >> /home/huangjian/crontab_demo/everymonth_1_11_21_31.txt
# 在 23 点，0 点到 7 点，每隔 1 分钟执行命令
* 23,0-7/1 * * * echo `date` >> /home/huangjian/crontab_demo/hour_0-7_23_every_minute.txt
# 在 23 点，0 点，2 点，4 点，6 点，每隔 1 分钟执行命令
* 23,0-7/2 * * * echo `date` >> /home/huangjian/crontab_demo/hour_0_2_4_6_23_every_minute.txt
# 每天的 3 点到 5 点，17 点到 20 点，每隔 30 分钟执行命令
*/30 3-5,17-20 * * * echo `date` >> /home/huangjian/crontab_demo/hour_3-5_17-20_every_30_minute.txt
# 每年的 8 月 20 号的 00:00 执行命令
0 0 20 8 * echo `date` >> /home/huangjian/crontab_demo/month_8_20th.txt
注意： 在有的 crontab 上，配置里面如果有空行也会报错，实在是太坑了。
可以使用 vim 的命令 :g/^$/d 来删除所有空行。
每分钟执行一次 test.sh
*/1 * * * * test.sh
上面这么写是有问题的，因为要用绝对路径，修改如下：
*/1 * * * * /bin/bash /home/huangjian/test.sh
每分钟输出一个当前时间到 /home/huangjian/foo.txt 文件末尾
*/1 * * * * echo `date` >> /home/huangjian/foo.txt
每天 00:00 执行一次
0 0 * * * test.sh
实际测试数据
every_1_minute.txt
# 每隔 1 分钟执行命令
*/1 * * * * echo `date` >> /home/huangjian/crontab_demo/every_1_minute.txt
Wed Sep 11 12:53:01 UTC 2019
Wed Sep 11 12:54:01 UTC 2019
Wed Sep 11 12:55:01 UTC 2019
Wed Sep 11 12:56:01 UTC 2019
Wed Sep 11 12:57:01 UTC 2019
Wed Sep 11 12:58:01 UTC 2019
Wed Sep 11 12:59:01 UTC 2019
Wed Sep 11 13:00:01 UTC 2019
Wed Sep 11 13:01:01 UTC 2019
Wed Sep 11 13:02:01 UTC 2019
Wed Sep 11 13:03:01 UTC 2019
every_2_minute.txt
你会发现，这个不仅仅是只隔两分钟，而且分钟数也是 2 的倍数。
# 每隔 2 分钟执行命令
*/2 * * * * echo `date` >> /home/huangjian/crontab_demo/every_2_minute.txt
Wed Sep 11 12:44:01 UTC 2019
Wed Sep 11 12:46:02 UTC 2019
Wed Sep 11 12:48:01 UTC 2019
Wed Sep 11 12:50:01 UTC 2019
Wed Sep 11 12:52:01 UTC 2019
Wed Sep 11 12:54:01 UTC 2019
Wed Sep 11 12:56:01 UTC 2019
Wed Sep 11 12:58:01 UTC 2019
Wed Sep 11 13:00:01 UTC 2019
Wed Sep 11 13:02:01 UTC 2019
Wed Sep 11 13:04:01 UTC 2019
Wed Sep 11 13:06:01 UTC 2019
Wed Sep 11 13:08:01 UTC 2019
Wed Sep 11 13:10:01 UTC 2019
Wed Sep 11 13:12:01 UTC 2019
Wed Sep 11 13:14:01 UTC 2019
Wed Sep 11 13:16:01 UTC 2019
Wed Sep 11 13:18:01 UTC 2019
every_3_minute.txt
每隔 3 分钟，并且分钟数也是 3 的倍数。
# 每隔 3 分钟执行命令
*/3 * * * * echo `date` >> /home/huangjian/crontab_demo/every_3_minute.txt
Wed Sep 11 12:42:01 UTC 2019
Wed Sep 11 12:45:02 UTC 2019
Wed Sep 11 12:48:01 UTC 2019
Wed Sep 11 12:51:01 UTC 2019
Wed Sep 11 12:54:01 UTC 2019
Wed Sep 11 12:57:01 UTC 2019
Wed Sep 11 13:00:01 UTC 2019
Wed Sep 11 13:03:01 UTC 2019
Wed Sep 11 13:06:01 UTC 2019
Wed Sep 11 13:09:01 UTC 2019
Wed Sep 11 13:12:01 UTC 2019
Wed Sep 11 13:15:01 UTC 2019
every_4_minute.txt
# 每隔 4 分钟执行命令
*/4 * * * * echo `date` >> /home/huangjian/crontab_demo/every_4_minute.txt
Wed Sep 11 12:44:01 UTC 2019
Wed Sep 11 12:48:01 UTC 2019
Wed Sep 11 12:52:01 UTC 2019
Wed Sep 11 12:56:01 UTC 2019
Wed Sep 11 13:00:01 UTC 2019
Wed Sep 11 13:04:01 UTC 2019
Wed Sep 11 13:08:01 UTC 2019
Wed Sep 11 13:12:01 UTC 2019
every_5_minute.txt
# 每隔 5 分钟执行命令
*/5 * * * * echo `date` >> /home/huangjian/crontab_demo/every_5_minute.txt
Wed Sep 11 12:45:02 UTC 2019
Wed Sep 11 12:50:01 UTC 2019
Wed Sep 11 12:55:01 UTC 2019
Wed Sep 11 13:00:01 UTC 2019
Wed Sep 11 13:05:01 UTC 2019
Wed Sep 11 13:10:01 UTC 2019
Wed Sep 11 13:15:01 UTC 2019
every_6_minute.txt
# 每隔 6 分钟执行命令
*/6 * * * * echo `date` >> /home/huangjian/crontab_demo/every_6_minute.txt
Wed Sep 11 12:42:01 UTC 2019
Wed Sep 11 12:48:01 UTC 2019
Wed Sep 11 12:54:01 UTC 2019
Wed Sep 11 13:00:01 UTC 2019
Wed Sep 11 13:06:01 UTC 2019
Wed Sep 11 13:12:01 UTC 2019
Wed Sep 11 13:18:01 UTC 2019
Wed Sep 11 13:24:01 UTC 2019
every_7_minute.txt
认真观察这个情况，你会发现，在 56 分的时候，下一个就变成了 00 了。
所以，这并不是严格的每隔 7 分钟执行一次。
# 每隔 7 分钟执行命令
*/7 * * * * echo `date` >> /home/huangjian/crontab_demo/every_7_minute.txt
Wed Sep 11 12:42:01 UTC 2019
Wed Sep 11 12:49:01 UTC 2019
Wed Sep 11 12:56:01 UTC 2019
Wed Sep 11 13:00:01 UTC 2019
Wed Sep 11 13:07:01 UTC 2019
Wed Sep 11 13:14:01 UTC 2019
Wed Sep 11 13:21:01 UTC 2019
Wed Sep 11 13:28:01 UTC 2019
Wed Sep 11 13:35:01 UTC 2019
Wed Sep 11 13:42:01 UTC 2019
Wed Sep 11 13:49:01 UTC 2019
Wed Sep 11 13:56:01 UTC 2019
Wed Sep 11 14:00:01 UTC 2019
Wed Sep 11 14:07:01 UTC 2019
every_hour_0th.txt
# 每小时的第 0 分钟执行命令
0 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_0th.txt
Wed Sep 11 13:00:01 UTC 2019
Wed Sep 11 14:00:01 UTC 2019
Wed Sep 11 15:00:01 UTC 2019
Wed Sep 11 16:00:01 UTC 2019
Wed Sep 11 17:00:01 UTC 2019
Wed Sep 11 18:00:01 UTC 2019
Wed Sep 11 19:00:01 UTC 2019
Wed Sep 11 20:00:01 UTC 2019
every_hour_1th.txt
# 每小时的第 1 分钟执行命令
1 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_1th.txt
Wed Sep 11 13:01:01 UTC 2019
Wed Sep 11 14:01:01 UTC 2019
Wed Sep 11 15:01:01 UTC 2019
Wed Sep 11 16:01:01 UTC 2019
Wed Sep 11 17:01:01 UTC 2019
Wed Sep 11 18:01:01 UTC 2019
Wed Sep 11 19:01:01 UTC 2019
every_hour_2th.txt
# 每小时的第 2 分钟执行命令
2 * * * * echo `date` >> /home/huangjian/crontab_demo/every_hour_2th.txt
Wed Sep 11 13:02:01 UTC 2019
Wed Sep 11 14:02:01 UTC 2019
Wed Sep 11 15:02:01 UTC 2019
Wed Sep 11 16:02:01 UTC 2019
Wed Sep 11 17:02:01 UTC 2019
Wed Sep 11 18:02:02 UTC 2019
Wed Sep 11 19:02:01 UTC 2019
everyday_01_00.txt
# 每天的 1 点时执行命令
0 1 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_01_00.txt
Thu Sep 12 01:00:01 UTC 2019
Fri Sep 13 01:00:01 UTC 2019
Sat Sep 14 01:00:01 UTC 2019
Sun Sep 15 01:00:01 UTC 2019
Mon Sep 16 01:00:01 UTC 2019
everyday_02_00.txt
# 每天的 2 点时执行命令
0 2 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_02_00.txt
Thu Sep 12 02:00:01 UTC 2019
Fri Sep 13 02:00:01 UTC 2019
Sat Sep 14 02:00:01 UTC 2019
Sun Sep 15 02:00:01 UTC 2019
Mon Sep 16 02:00:01 UTC 2019
everyday_24_00.txt
# 每天的 0 点时执行命令
0 0 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_24_00.txt
Thu Sep 12 00:00:01 UTC 2019
Fri Sep 13 00:00:01 UTC 2019
Sat Sep 14 00:00:01 UTC 2019
Sun Sep 15 00:00:01 UTC 2019
Mon Sep 16 00:00:01 UTC 2019
everyday_6-12_hour_every_3_hour.txt
# 每天的 6 点到 12 点之间，每隔 3 小时执行命令
0 6-12/3 * * * echo `date` >> /home/huangjian/crontab_demo/everyday_6-12_hour_every_3_hour.txt
Thu Sep 12 06:00:01 UTC 2019
Thu Sep 12 09:00:01 UTC 2019
Thu Sep 12 12:00:01 UTC 2019
Fri Sep 13 06:00:01 UTC 2019
Fri Sep 13 09:00:01 UTC 2019
Fri Sep 13 12:00:01 UTC 2019
Sat Sep 14 06:00:01 UTC 2019
Sat Sep 14 09:00:01 UTC 2019
Sat Sep 14 12:00:02 UTC 2019
