How to make command-line options mandatory with GLib?
c, glib, optional-parameters
Solution
It's up to you to check argument sanity (beyond parsing), that goes for `getopt` as well. The problem is, when making things 'mandatory', you will often run into cases where 'mandatory' applies only in the absence of other arguments.
For instance, `./program --help` should require no additional arguments, likewise for `./program --version`. Putting the logic of "require --foo and --bar unless --version OR --help" in the parser itself would border on bloat and overcomplexity.
You simply must check the value of `line` and `column` after arguments are parsed to ensure that they were set to something. It's entirely possible to put all of that logic into a function (e.g. `check_sanity()`) if you are worried about clutter in `main()`.
In summary, the behavior that you are seeing is by design, I don't think it's likely to change. If either variable remains as it was initialized after the parser runs, the user forgot to specify the respective option.
Problem
I use GLib to parse some command-line options. The problem is that I want to make two of those options mandatory so that the program terminates with the help screen if the user omits them. My code looks like this: ``` static gint line = -1; static gint column = -1; static GOptionEntry options[] = { {"line", 'l', 0, G_OPTION_ARG_INT, &line, "The line", "L"}, {"column", 'c', 0, G_OPTION_ARG_INT, &column, "The column", "C"}, {NULL} }; ... int main(int argc, char** argv) { GError *error = NULL; GOptionContext *context; context = g_option_context_new ("- test"); g_option_context_add_main_entries (context, options, NULL); if (!g_option_context_parse(context, &argc, &argv, &error)) { usage(error->message, context); } ... return 0; } ``` If I omit one of those parameters or both on the command-line g_option_context_parse() still succeeds and the values in question (line and or column) are still -1. How can I tell GLib to fail parsing if the user doesn't pass both options on the command-line? Maybe I'm just blind but I couldn't find a flag I can put into my GOptionEntry data structure to tell it to make those fields mandatory. Of course I could check if one of those variables is still -1 but then the user could just have passed this value on the command-line and I want to print a separate error message if the values are out of range.