指定可选参数的正确语法是什么?

有两种选择:使用“|”作为“或”符号和非方括号进行分组以避免“可选”上下文,或者在多行上列出相互竞争的用法

perl mysrc.pl {-a=<value of a> -b=<value of b> -c=<value of c>|-t=<value of t>}

perl mysrc.pl UseCaseOneOptions|UseCaseTwoOptions
     UseCaseOneOptions: -a=<value of a> -b=<value of b> -c=<value of c>
     UseCaseTwoOptions: -t=<value of t>

$ cvs --help
  Usage: cvs <command> <per-command-options>
  Please type "cvs command --help" to get help on specific command's options
  Commands are: 
      cvs add
      cvs commmit
      cvs remove
      ...

$ cvs checkout --help
  Usage: cvs checkout [-p] [-A] [-m message] [-M message_file] file_path
      -m message:          check-in comment
      -M file:             read check-in comment from this file
      -p:                  non-sticky checkout. Print the file to STDOUT.

$ cvs diff --help
  Usage: cvs diff [-r VER1] [-r VER2] [-w] file_path
       -w:                 Ignore whitespace

我可能会用:

mycmd [ -t=tval | -a=aval -b=bval -c=cval ] ...

{} '而不是方括号' [] '. 方括号通常表示“可选”。

你是说帮助短信?在这种情况下,您可以执行Subversion所做的操作,例如:

$ svn help merge
merge: Apply the differences between two sources to a working copy path.
usage: 1. merge sourceURL1[@N] sourceURL2[@M] [WCPATH]
       2. merge sourceWCPATH1@N sourceWCPATH2@M [WCPATH]
       3. merge [-c M[,N...] | -r N:M ...] SOURCE[@REV] [WCPATH]