Re: show help if no input

  On 8/18/10 5:42 AM, Lorenzo Bettini wrote:
> On 17/08/2010 22.15, Duke wrote:
>>  Hi folks,
>>
> Hi there

Hi Lorenzo,

>> I just heard about gengetopt, tried it and like it very much. I want 
>> to change the default reaction of gengetopt a little bit to suit my 
>> purpose better, so I have two questions below:
>>
>>  * When Print help, is there a way showing that one option is 
>> optional and the other is required? For now, help shows only options 
>> and their descriptions and values, no way to know if an option is 
>> optional or required until one tries the program and some of its 
>> options.
>>
> for the moment this is not implemented, although in the summary of 
> command invocation optional options should be printed differently (I 
> should check this, I don't remember it right now and cannot check it 
> now).

I am new to gengetopt, so I am not quite sure what you mentioned. What 
is the "summary of command invocation"? Is it printed when "-h" is used, 
or one has to use another option?

>
> Surely, this behavior could be added (by using a command line switch 
> of gengetopt itself); I should work on this (or if you want to try to 
> implement it...)

Well, it is quite beyond my ability now. I am just a learner in C/C++. 
But I am willing to assist if possible.

>>  * When there is no input (no argument or argc < 2), is there a way 
>> of telling gengetopt to show help, even if there are required 
>> options? For now, if there is required option, and if the program is 
>> invoked without argument, then "option required" shows up, not the help.
>>
> this could be implemented in your program itself; as long as you init 
> an args_info structure, then you could check argc and in case call the 
> print help generated function directly; have you tried this?

I might have missed something/some options, but here is what I tried:

     gengetopt_args_info args_info;
     if ( cmdline_parser (argc, argv, &args_info) != 0 ) {
         return 1;
     }

     string Input;
     if ( argc >= 2 && args_info.inputs_num == 1 ) {
         Input = args_info.inputs[0];
     } else {
         if ( argc < 2 ) {
             return usage( args_info, false );
         } else if ( args_info.help_given ) {
             return usage( args_info, true );
         } else if ( args_info.inputs_num == 0 ) {
             cerr << "No input file. Program aborts!" << endl;
         } else if ( args_info.inputs_num > 1 ) {
             cerr << "Too many input files. Program aborts!" << endl;
         }
         return ProgramExit(args_info);
     }

where

int ProgramExit( gengetopt_args_info args_info ) {
     cmdline_parser_free (&args_info);
     return -1;
}

So basically when there is no input (no argument, or argc < 2), help 
should be printed. This works only if I do not have any required option. 
If there is one required option, "option required" notification will 
show up. I think the condition to show "option required" is not just 
args_info.(some_option)_given, but also argc >= 2 in this situation. 
What do you think?

Thanks,

D.