1 use std::env;
2 use std::error::Error;
3 use std::ffi::OsString;
4 use std::process;
5
run() -> Result<(), Box<dyn Error>>6 fn run() -> Result<(), Box<dyn Error>> {
7 let file_path = get_first_arg()?;
8 let mut wtr = csv::Writer::from_path(file_path)?;
9
10 wtr.write_record(&[
11 "City",
12 "State",
13 "Population",
14 "Latitude",
15 "Longitude",
16 ])?;
17 wtr.write_record(&[
18 "Davidsons Landing",
19 "AK",
20 "",
21 "65.2419444",
22 "-165.2716667",
23 ])?;
24 wtr.write_record(&["Kenai", "AK", "7610", "60.5544444", "-151.2583333"])?;
25 wtr.write_record(&["Oakman", "AL", "", "33.7133333", "-87.3886111"])?;
26
27 wtr.flush()?;
28 Ok(())
29 }
30
31 /// Returns the first positional argument sent to this process. If there are no
32 /// positional arguments, then this returns an error.
get_first_arg() -> Result<OsString, Box<dyn Error>>33 fn get_first_arg() -> Result<OsString, Box<dyn Error>> {
34 match env::args_os().nth(1) {
35 None => Err(From::from("expected 1 argument, but got none")),
36 Some(file_path) => Ok(file_path),
37 }
38 }
39
main()40 fn main() {
41 if let Err(err) = run() {
42 println!("{}", err);
43 process::exit(1);
44 }
45 }
46