Merge pull request #3 from CleanCut/clap-derive

Clap derive

Cargo.toml

@@ -13,4 +13,4 @@ license = "MIT OR Apache-2.0"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-clap = "3.2.21"
+clap = { version = "3.2.21", features = ["derive"] }

src/opts.rs

@@ -1,57 +1,33 @@
-use clap::{App, Arg};
+use clap::Parser;
 
-#[derive(Debug)]
+#[derive(Debug, clap::Parser)]
 pub struct Opts {
+    #[clap(help = "Read from a file instead of stdin")]
     pub filename: Option<String>,
+    #[clap(
+        help = "Number of first lines of a file to display",
+        short = 'H',
+        long = "head",
+        default_value_t = 10
+    )]
     pub head: usize,
+    #[clap(
+        help = "Number of last lines of a file to display",
+        short = 'T',
+        long = "tail",
+        default_value_t = 10
+    )]
     pub tail: usize,
+    #[clap(
+        help = "Wait for additional data to be appended to a file. Ignored if standard input is a pipe.",
+        short = 'f',
+        long = "follow"
+    )]
     pub follow: bool,
 }
 
 impl Opts {
     pub fn parse_args() -> Self {
-        let matches = App::new("headtail")
-            .arg(Arg::with_name("filename").help("Read from a file instead of stdin"))
-            .arg(
-                Arg::with_name("head")
-                    .short('H')
-                    .long("head")
-                    .takes_value(true)
-                    .default_value("10")
-                    .help("Number of first lines of a file to display"),
-            )
-            .arg(
-                Arg::with_name("tail")
-                    .short('T')
-                    .long("tail")
-                    .takes_value(true)
-                    .default_value("10")
-                    .help("Number of last lines of a file to display"),
-            )
-            .arg(
-                Arg::with_name("follow")
-                    .short('f')
-                    .long("follow")
-                    .help("Wait for additional data to be appended to a file. Ignored if standard input is a pipe."),
-            )
-            .get_matches();
-        let filename = matches.value_of("filename").map(|f| f.to_string());
-        let head = matches
-            .value_of("head")
-            .unwrap()
-            .parse::<usize>()
-            .expect("could not parse number for head"); // TODO: more graceful error handling
-        let tail = matches
-            .value_of("tail")
-            .unwrap()
-            .parse::<usize>()
-            .expect("could not parse number for tail"); // TODO: more graceful error handling
-        let follow = matches.is_present("follow");
-        Self {
-            filename,
-            head,
-            tail,
-            follow,
-        }
+        Self::parse()
     }
 }