1 files changed, 41 insertions, 0 deletions
diff --git a/clap/examples/16_app_settings.rs b/clap/examples/16_app_settings.rs
new file mode 100644
index 0000000..ab1d185
--- /dev/null
+++ b/clap/examples/16_app_settings.rs
@@ -0,0 +1,41 @@
+extern crate clap;
+
+use clap::{App, AppSettings, SubCommand};
+
+fn main() {
+    // You can use AppSettings to change the application level behavior of clap. .setting() function
+    // of App struct takes AppSettings enum as argument. There is also .settings() function which
+    // takes slice of AppSettings enum.  You can learn more about AppSettings in the documentation,
+    // which also has examples on each setting.
+    //
+    // This example will only show usage of one AppSettings setting. See documentation for more
+    // information.
+
+    let matches = App::new("myapp")
+                        .setting(AppSettings::SubcommandsNegateReqs)
+                                            // Negates requirement of parent command.
+
+                        .arg_from_usage("<input> 'input file to use'")
+                                            // Required positional argument called input.  This
+                                            // will be only required if subcommand is not present.
+
+                        .subcommand(SubCommand::with_name("test")
+                                                .about("does some testing"))
+                                            // if program is invoked with subcommand, you do not
+                                            // need to specify the <input> argument anymore due to
+                                            // the AppSettings::SubcommandsNegateReqs setting.
+
+                        .get_matches();
+
+    // Calling unwrap() on "input" would not be advised here, because although it's required,
+    // if the user uses a subcommand, those requirements are no longer required. Hence, we should
+    // use some sort of 'if let' construct
+    if let Some(inp) = matches.value_of("input") {
+        println!("The input file is: {}", inp);
+    }
+
+    match matches.subcommand() {
+        ("test", _) => println!("The 'test' subcommand was used"),
+        _           => unreachable!()
+    }
+}