(2>/dev/null crontab -l ; echo "0 3 * * * /usr/local/bin/certbot-auto renew") | crontab -

cat <(crontab -l 2>/dev/null) <(echo "0 3 * * * /usr/local/bin/certbot-auto renew") | crontab -

#输出当前crontab

crontab -l > mycron 2>/dev/null

#echo new cron到cron文件中

echo "0 3 * * * /usr/local/bin/certbot-auto renew" >> mycron

#安装新的cron文件

crontab mycron

rm mycron

您可以向crontab添加如下内容:

#write out current crontab
crontab -l > mycron
#echo new cron into cron file
echo "00 09 * * 1-5 echo hello" >> mycron
#install new cron file
crontab mycron
rm mycron

Cron行解释

* * * * * "command to be executed"
- - - - -
| | | | |
| | | | ----- Day of week (0 - 7) (Sunday=0 or 7)
| | | ------- Month (1 - 12)
| | --------- Day of month (1 - 31)
| ----------- Hour (0 - 23)
------------- Minute (0 - 59)

nixCraft来源。

谢谢大家的帮助。把我在这里和其他地方的发现拼凑起来，我得出了这个结论:

的代码

command="php $INSTALL/indefero/scripts/gitcron.php"
job="0 0 * * 0 $command"
cat <(fgrep -i -v "$command" <(crontab -l)) <(echo "$job") | crontab -

我想不出如何在不重复自己的情况下消除对这两个变量的需求。

命令显然是我想调度的命令。Job接受$命令并添加调度数据。我需要在执行工作的代码行中分别使用这两个变量。

细节

Credit to duckyflip, I use this little redirect thingy (<(*command*)) to turn the output of crontab -l into input for the fgrep command. fgrep then filters out any matches of $command (-v option), case-insensitive (-i option). Again, the little redirect thingy (<(*command*)) is used to turn the result back into input for the cat command. The cat command also receives echo "$job" (self explanatory), again, through use of the redirect thingy (<(*command*)). So the filtered output from crontab -l and the simple echo "$job", combined, are piped ('|') over to crontab - to finally be written. And they all lived happily ever after!

简而言之:

这行代码过滤掉与命令匹配的任何cron作业，然后用新的cron作业写出剩余的cron作业，有效地充当“添加”或“更新”函数。 要使用它，您所要做的就是替换命令和作业变量的值。

echo "0 * * * * docker system prune --force >/dev/null 2>&1" | sudo tee /etc/cron.daily/dockerprune

Bash脚本，用于在没有交互式编辑器的情况下添加cron作业。 下面的代码帮助您使用linux文件添加cronjob。

#!/bin/bash

cron_path=/var/spool/cron/crontabs/root

#cron job to run every 10 min.
echo "*/10 * * * * command to be executed" >> $cron_path

#cron job to run every 1 hour.
echo "0 */1 * * * command to be executed" >> $cron_path

编辑(固定覆盖):

cat <(crontab -l) <(echo "1 2 3 4 5 scripty.sh") | crontab -