用可选参数编写鱼壳脚本

我有一个鱼壳脚本,它的默认行为是在完成时发送电子邮件。我想修改它以回应 nomail 来自命令行的参数。例如,运行脚本通常会生成一封电子邮件:

michaelmichael: ~/bin/myscript

但如果和 提名 切换,它不会发送确认电子邮件:

michaelmichael: ~/bin/myscript nomail

如果我用 提名 争论,一切正常。没有 提名 , $argv is undefined and it throws an error. I've scoured the fish shell documentation, but can't seem to find anything that will work. Here's what I have so far

switch $argv
  case nomail
    ## Perform normal script functions
  case ???
    ## Perform normal script functions
    mailx -s "Script Done!"
end

运行此操作会引发以下错误:

switch: Expected exactly one argument, got 0

Obviously it expects an argument, I just don't know the syntax for telling it to accept no arguments, or one if it exists.

我猜这是非常基本的,但我只是不太了解shell脚本。