Restarted the production of the app

libs/CLI11/examples/subcom_in_files/CMakeLists.txt

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+add_cli_exe(subcommand_main subcommand_main.cpp subcommand_a.cpp subcommand_a.hpp)

libs/CLI11/examples/subcom_in_files/subcommand_a.cpp

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+// Copyright (c) 2017-2022, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "subcommand_a.hpp"
+#include <iostream>
+#include <memory>
+
+/// Set up a subcommand and capture a shared_ptr to a struct that holds all its options.
+/// The variables of the struct are bound to the CLI options.
+/// We use a shared ptr so that the addresses of the variables remain for binding,
+/// You could return the shared pointer if you wanted to access the values in main.
+void setup_subcommand_a(CLI::App &app) {
+    // Create the option and subcommand objects.
+    auto opt = std::make_shared<SubcommandAOptions>();
+    auto *sub = app.add_subcommand("subcommand_a", "performs subcommand a");
+
+    // Add options to sub, binding them to opt.
+    sub->add_option("-f,--file", opt->file, "File name")->required();
+    sub->add_flag("--with-foo", opt->with_foo, "Counter");
+
+    // Set the run function as callback to be called when this subcommand is issued.
+    sub->callback([opt]() { run_subcommand_a(*opt); });
+}
+
+/// The function that runs our code.
+/// This could also simply be in the callback lambda itself,
+/// but having a separate function is cleaner.
+void run_subcommand_a(SubcommandAOptions const &opt) {
+    // Do stuff...
+    std::cout << "Working on file: " << opt.file << std::endl;
+    if(opt.with_foo) {
+        std::cout << "Using foo!" << std::endl;
+    }
+}

libs/CLI11/examples/subcom_in_files/subcommand_a.hpp

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+// Copyright (c) 2017-2022, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#pragma once
+
+#include <CLI/CLI.hpp>
+#include <string>
+
+/// Collection of all options of Subcommand A.
+struct SubcommandAOptions {
+    std::string file;
+    bool with_foo;
+};
+
+// We could manually make a few variables and use shared pointers for each; this
+// is just done this way to be nicely organized
+
+// Function declarations.
+void setup_subcommand_a(CLI::App &app);
+void run_subcommand_a(SubcommandAOptions const &opt);

libs/CLI11/examples/subcom_in_files/subcommand_main.cpp

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+// Copyright (c) 2017-2022, University of Cincinnati, developed by Henry Schreiner
+// under NSF AWARD 1414736 and by the respective contributors.
+// All rights reserved.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "subcommand_a.hpp"
+#include <CLI/CLI.hpp>
+
+int main(int argc, char **argv) {
+    CLI::App app{"..."};
+
+    // Call the setup functions for the subcommands.
+    // They are kept alive by a shared pointer in the
+    // lambda function held by CLI11
+    setup_subcommand_a(app);
+
+    // Make sure we get at least one subcommand
+    app.require_subcommand();
+
+    // More setup if needed, i.e., other subcommands etc.
+
+    CLI11_PARSE(app, argc, argv);
+
+    return 0;
+}