parse command line args in form /variable=value ?

pmh4514

Hi,

What's the "Qt Way" of parsing command line arguments in this form:

my.exe /var1=value1 /var2=value2 /var3=value3

etc?

I need to make my Qt app (which is being ported from MFC ) launchable by an existing 3rd-party tool that is already coded to launch my (MFC) app with arguments in this "non traditional" form and QCommandLineParser and QCommandLineOption seem more suited to the more traditional "--option" type approach. I want to make my new Qt version work the same without having to make changes to the 3rd party tool which is calling mine.

Do I have to just manually parse things using RegEx (etc) or am I missing something?

Thanks!

Paul Colby

Hi @pmh4514,

I want to make my new Qt version work the same without having to make changes to the 3rd party tool which is calling mine.

I think there's two approaches you could take here.

First, you could treat all arguments as positional arguments, and parse them yourself. It wouldn't be too hard, like:

QCoreApplication app(argc, argv);

QCommandLineParser parser;
parser.addHelpOption();
parser.addPositionalArgument("args", "Arguments in the old MFC app's style, eg /var1=value1", "[args...]");
parser.process(app);

foreach (const QString &arg, parser.positionalArguments()) {
    if (arg.startsWith('/')) {
        qDebug() << "Arg" << arg.section('=',0,0).mid(1) << "set to" << arg.section('=',1);
    }
}

If we execute that like: ./foo -h we get:

Usage: ./foo [options] [args...]

Options:
  -h, --help  Displays this help.

Arguments:
  args        Arguments in the old MFC app's style, eg /var1=value1

Then, if we execute like: ./foo /a=1 "/bbb=123=456" we get:

Arg "a" set to "1"
Arg "bbb" set to "123=456"

However, another approach, which may or may not be preferable, is to manipulate the arguments before calling the parser, like:

QCoreApplication app(argc, argv);

QStringList arguments;
foreach (auto arg, app.arguments()) {
    if (arg.startsWith('/')) {
        arg.replace(0,1,"--");
    }
    arguments.append(arg);
}

QCommandLineParser parser;
parser.addHelpOption();
parser.addOptions({
    // Just for example
    {{"a", "aaa"}, "Some option", "val"},
    {{"b", "bbb"}, "Some other option", "val"},
});
parser.process(arguments);

qDebug() << "Arg a is" << parser.value("a");
qDebug() << "Arg b is" << parser.value("b");

Now if we run ./foo -h:

Usage: ./foo [options]

Options:
  -h, --help       Displays this help.
  -a, --aaa <val>  Some option
  -b, --bbb <val>  Some other option

And ./foo /a=1 "/bbb=123=456"

Arg a is "1"
Arg b is "123=456"

The second version has the advantage of supporting both the -a --bbb and /a /bbb styles. They can even be mixed and matched.

Hope that helps.

Cheers.

pmh4514

very helpful. Thank you!