Parsing long and short arguments with the flag package

[Alexander Rødseth]

Hello,

I'm using the "flag" package to parse command line arguments for my
tiny app "addinclude" [1], which is my very first application written
in Go.
However, I can't find an elegant way to check for long and short
versions of arguments (like "-v" and "--version").

This is what I ended up with in the latest version (I was parsing
flag.Args() myself in earlier versions):

nofix_text := "don't change the include text"
top_text := "add the include at the top"
version_text := "show the current version"
help_text := "this brief help"
test_text := "perform self testing"

var nofix_long *bool = flag.Bool("nofix", false, nofix_text)
var nofix_short *bool = flag.Bool("n", false, nofix_text)
var top_long *bool = flag.Bool("top", false, top_text)
var top_short *bool = flag.Bool("t", false, top_text)
var version_long *bool = flag.Bool("version", false, version_text)
var version_short *bool = flag.Bool("v", false, version_text)
var help_long *bool = flag.Bool("help", false, help_text)
var help_short *bool = flag.Bool("h", false, help_text)
var test_long *bool = flag.Bool("test", false, test_text)

flag.Parse()

nofix := *nofix_long || *nofix_short
top := *top_long || *top_short
version := *version_long || *version_short
help := *help_long || *help_short
test := *test_long

I don't find this particularly elegant, but I stuck to what felt most
like "the blessed way of parsing arguments in Go".

Is there a better or more elegant way of doing this in Go?

Here's the app:
1. http://addinclude.roboticoverlords.org/

Thanks.

Best regards,
Alexander Rødseth

[Gustavo Niemeyer]

Hi Alexander,

> However, I can't find an elegant way to check for long and short
> versions of arguments (like "-v" and "--version").

(...)

>  var nofix_long *bool = flag.Bool("nofix", false, nofix_text)
>  var nofix_short *bool = flag.Bool("n", false, nofix_text)

Try this:

var nofix = flag.Bool("nofix", false, "help")

func init() {
flag.BoolVar(nofix, "n", false, "help")
}

With some work you can probably define an Alias function to do this
automatically.

--
Gustavo Niemeyer
http://niemeyer.net
http://niemeyer.net/blog
http://niemeyer.net/twitter

[Russ Cox]

But note that even with Gustavo's nice suggestion
you still do not end up with true getopt-like flag parsing:
--n and -nofix would be accepted too, and -nv would not
be the same as -n -v. The behavior in package flag
mimics the behavior in
http://code.google.com/p/google-gflags/
not the traditional GNU behavior.

I believe that others have written more GNU-like
command line flag parsers.

Russ

[David Roundy]

Indeed, one example of a more gnu-getopt-like argument parser would be:

https://github.com/droundy/goopt

Its API is still a bit rough, but it works for the things I've wanted
to do with it (including generating man pages, for instance).

David

--
David Roundy

[jimt]

And another one:

https://github.com/jteeuwen/go-pkg-optarg

This one also has pretty-printing of the Usage() command. Which means nicely aligned output. This includes ordering commands into categories for even more understandable output. Handy if you have a large amount of options.