在这种情况下，Google无用，因为搜索标志无用

Google is useless in this case because searching for flags is useless

幸运的是， Bash参考手册可在线获得，网址为 http://www.gnu.org/software/bash/manual/bashref.html .当您在Google上搜索打击手册"时，这是第一个热门歌曲. § 6.4"Bash条件表达式" 说:

Fortunately, the Bash Reference Manual is available online, at http://www.gnu.org/software/bash/manual/bashref.html. It's the first hit when you Google for "Bash manual". §6.4 "Bash Conditional Expressions" says:

-f file

-f file

如果 file 存在并且是常规文件，则为真.

True if file exists and is a regular file.