read_lines
The method lines()
returns an iterator over the lines
of a file.
File::open
expects a generic, AsRef<Path>
. That's what
read_lines()
expects as input.
use std::fs::File; use std::io::{self, BufRead}; use std::path::Path; fn main() { // File hosts must exist in current path before this produces output if let Ok(lines) = read_lines("./hosts") { // Consumes the iterator, returns an (Optional) String for line in lines { if let Ok(ip) = line { println!("{}", ip); } } } } // The output is wrapped in a Result to allow matching on errors // Returns an Iterator to the Reader of the lines of the file. fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>> where P: AsRef<Path>, { let file = File::open(filename)?; Ok(io::BufReader::new(file).lines()) }
Running this program simply prints the lines individually.
$ echo -e "127.0.0.1\n192.168.0.1\n" > hosts
$ rustc read_lines.rs && ./read_lines
127.0.0.1
192.168.0.1
This process is more efficient than creating a String
in memory
especially working with larger files.