I'm looking for a reference regarding the syntax of the help displayed for a dos command.
I didn't find anything with Google.
I need this because I'm writing a batch and I want to provide help for this batch regarding arguments and options.
I know I could deduce it from the help of existing dos commands, but it would be great if there was a full reference about it.
You mean the syntax as in the following?
findstr [/b] [/e] [/l] [/r] [/s] [/i] [/x] [/v] [/n] [/m] [/o] [/p] [/offline] [/g:file] [/f:file] [/c:string] [/d:dirlist] [/a:ColorAttribute] [strings] [[Drive:][Path] FileName [...]]
That's easy. Things in square brackets can be omitted. The [...] at the end indicates that you can supply more files if you wish, it doesn't have to be just one.
There are also alternatives sometimes:
attrib [{+r|-r}] [{+a|-a}] [{+s|-s}] [{+h|-h}] [[Drive:][Path] FileName] [/s[/d]]
indicated by curly braces while alternatives are separated by |. Also noteworthy here: /d at the end is only valid if you also provided /s since there are two nested levels of brackets.
There is no strict syntax definition and you can usually figure out some other aspects, like the [...] on your own. Many examples need a bit interpretation (which mostly is obvious, though). E.g. date:
date [mm-dd-yy] [/t]
You can supply a date in a weird format as the first argument, but that's very easy to guess. And no, it doesn't tell you to supply literally mm-dd-yy, but that's why humans read that description, not machines.
EDIT: I just noticed that Technet even gives a summary of the syntax at the bottom of each article:
cmdis not DOS. I chose not to delete those references since what you're asking also applies to DOS. Still, the Windows Command Processor only shares tiny bits of syntax and idiosyncrasies with DOS. And perhaps the gray-text-on-black color scheme.