Start parsing command line and reading input file

src/main.rs

@@ -0,0 +1,41 @@
+use std::fs::File;
+use std::io::{self, BufRead, BufReader, Read};
+use std::path::PathBuf;
+use structopt::StructOpt;
+
+#[derive(Debug, StructOpt)]
+#[structopt(name = "choose", about = "`choose` sections from each line of files")]
+struct Opt {
+    /// Specify field separator other than whitespace
+    #[structopt(short, long, default_value = "")]
+    field_separator: String,
+
+    /// Use inclusive ranges
+    #[structopt(short, long)]
+    inclusive: bool,
+
+    /// Activate debug mode
+    #[structopt(short, long)]
+    debug: bool,
+
+    /// Input file
+    #[structopt(parse(from_os_str))]
+    input: Option<PathBuf>,
+}
+
+fn main() {
+    let opt = Opt::from_args();
+
+    let read = match &opt.input {
+        Some(f) => Box::new(File::open(f).expect("Could not open file")) as Box<Read>,
+        None => Box::new(io::stdin()) as Box<Read>,
+    };
+
+    let buf = BufReader::new(read);
+
+    for line in buf.lines() {
+        println!("{}", line.unwrap());
+    }
+
+    println!("Hello, world!");
+}