Linux ~ anacrontab中identifier有哪些作用?

man anacron帮助中有下面这样的一句描述:

Anacron only considers jobs whose identifier, as specified in anacrontab(5), matches any of the job command-line arguments. The job command-line arguments can be represented by shell wildcard patterns (be sure to protect them from your shell with adequate quoting). Specifying no job command-line arguments is equivalent to specifying "*" (that is, all jobs are considered by Anacron).

请问上面提到的通配符是什么情况下用到呢?还有这句话主要讲的什么意思?英文不好,没看明白。谢谢了

http://www.2cto.com/os/201208/146487.html