What is the English abbreviation for the atd service in linux? Describe the purpose and implementation of this service.

atd是“定时执行守护程序”的缩写，它是一个后台服务，用于计划性地执行一些命令或脚本。该服务通过检查每个用户的at（安排任务）文件，按照指定时间执行其中的命令。这些命令通常是一次性的，可以是简单的shell脚本或一些复杂的应用程序。atd服务很容易配置和使用，支持各种参数，例如运行时间、优先级等。|atd stands for "at daemon", which is a background service used to schedule the execution of commands or scripts. This service checks each user's at (schedule task) file and executes the commands specified at the specified time. These commands are usually one-time and can be simple shell scripts or more complex applications. The atd service is easy to configure and use, and supports various parameters such as runtime and priority.