linux - 使用 Bash 脚本添加到 Crontab(如果不存在)

Question

bash 脚本将作业添加到 crontab 的正确方法是什么，例如

不会有重复的工作

不会使用 crontab 文件

(可选)接近单线

在下面遇到了这个解决方案，但它不影响运行 crontab -l 的输出.

grep 'some_user python /mount/share/script.py' /etc/crontab || echo '*/1 *  *  *  * some_user python /mount/share/script.py' >> /etc/crontab

尝试将其转换为影响 crontab -l ,

(crontab -l | grep '/mount/share/script.py') || { crontab -l; '*/1 * * * * some_user python /mount/share/script.py >> /root/foo/logs/foo.cron.log 2>&1'; } | crontab -

但运行此命令会出现错误:

-bash: */1 * * * * some_user python /mount/share/script.py >> /root/foo/logs/foo.cron.log 2>&1: No such file or directory

Answer 1

but running this command gives the error:

-bash: */1 * * * * some_user python /mount/share/script.py >> /root/foo/logs/foo.cron.log 2>&1: No such file or directory

编码:

(crontab -l | grep '/mount/share/script.py') || { crontab -l; '*/1 * * * * some_user python /mount/share/script.py >> /root/foo/logs/foo.cron.log 2>&1'; } | crontab -

将尝试执行/运行:

'*/1 * * * * some_user python /mount/share/script.py >> /root/foo/logs/foo.cron.log 2>&1'

如果和何时 grep失败的。

在它前面添加一个 echo 或 printf，因为 crontab期待来自 stdin 的输入，就像您在第一个示例/代码中所做的那样，例如:

(crontab -l | grep '/mount/share/script.py') || { crontab -l; echo '*/1 * * * * some_user python /mount/share/script.py >> /root/foo/logs/foo.cron.log 2>&1'; } | crontab -

这是一个替代方案，它是一个完整的脚本。

#!/usr/bin/env bash

cron_entry=$(crontab -l 2>&1)
is_in_cron='/mount/share/script.py'
new_cron_entry='*/1 * * * * some_user python /mount/share/script.py >> /tmp/foo/logs/foo.cron.log 2>&1'

if [[ $cron_entry != *"$is_in_cron"* ]]; then
  printf '%s\n' "$cron_entry" "$new_cron_entry" | crontab -
fi