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Re: [help-gengetopt] show help if no input

From: Duke
Subject: Re: [help-gengetopt] show help if no input
Date: Wed, 18 Aug 2010 10:26:30 -0400
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv: Gecko/20100802 Lightning/1.0b2 Thunderbird/3.1.2

 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);


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?



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