String argument with optional value in std.getopt

[Hassan]

Thanks for the reply Steve

On Sunday, 9 August 2020 at 12:20:16 UTC, Steven Schveighoffer 
wrote:
> 2. If your optional parameters are not tied to the option 
> itself, then don't accept them via getopt. In other words, if 
> `hashtrack filter` is supposed to be valid, then filter isn't 
> an option after all, it's a standard parameter.

"filter" can be any string really. It's like an input to the list 
option : hashtrack --list filter_by_this_word

I wasn't aware that there was a distinction between parameters 
and options. The tool I'm writing is a D port of an existing Go 
command line utility that uses parameters everywhere, things like 
"hashtrack list" instead of "hashtrack --list". I decided to use 
options as opposed to parameters because then I would get to use 
getopt to handle "args" and display a nicely formatted --help 
output.

I decided to go with this second solution even though "hashtrack 
filter" isn't technically valid. Here's what I did :

void main()
{
     //....
     bool list;

     auto opts = args.getopt(
         "login", "Creates a session token and store it in the 
local filesystem in a config file", &login,
         "logout", "Remove the locally stored session token", 
&logout,
         "track", "Tracks one or more hashtags", &track,
         "untrack", "Untracks one or more previously tracked 
hashtags", &untrack,
         "tracks", "Displays the hashtags you are tracking", 
&tracks,
         "list", "Displays the latest 50 captured tweets", &list,
         "watch", "Stream and display the captured tweets in 
real-time", &watch,
         "status", "Displays who you are, if logged in", &status,
         "endpoint", "Point to another server", &endpoint,
         "config", "Load a custom config file", &config
     );
     //....
     if(list)
     {
         string filter = args.length > 1 ? args[1] : "";
         tracking.list(filter).each!writeln;
     }
}