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--- /dev/null
+/*
+ * Goals:
+ * - Parse command line arguments.
+ * - Read a file line by line.
+ * - Read stdin
+ * - Use regexp to match a line.
+ */
+
+use std::{ fs::File, io::{ self, BufReader, prelude::* } };
+use regex::Regex;
+use clap::{ App, Arg };
+
+fn main() {
+ let args = App::new("grep-lite")
+ .version("0.1")
+ .about("searches for patterns")
+ .arg(Arg::with_name("pattern")
+ .help("The pattern to search for")
+ .takes_value(true)
+ .required(true)
+ )
+ .arg(Arg::with_name("file")
+ .help("File to search into. Read from stding if not given")
+ .takes_value(true)
+ .required(false)
+ )
+ .get_matches();
+
+ let pattern = args.value_of("pattern").unwrap();
+ let pattern_re = Regex::new(pattern).unwrap();
+
+ match args.value_of("file") {
+ Some(filename) => {
+ let file = File::open(filename).unwrap();
+ let reader = BufReader::new(file);
+ process_lines(reader, pattern_re);
+ },
+ None => {
+ let stdin = io::stdin();
+ let reader = stdin.lock();
+ process_lines(reader, pattern_re);
+ }
+ }
+}
+
+fn process_lines<T: BufRead + Sized>(reader: T, pattern_re: Regex) {
+ for (i, line_result) in reader.lines().enumerate() {
+ match line_result {
+ Ok(line) => {
+ let contains_substring = pattern_re.find(&line);
+ match contains_substring {
+ Some(_) => println!("Found \"{}\" at line number {}", pattern_re, i + 1),
+ None => (),
+ }
+ },
+ Err(err) =>
+ eprintln!("Can't read line: {}", err)
+ }
+ }
+}