Better error handling, database file as input option

city-pop/src/main.rs

@@ -4,7 +4,7 @@ extern crate csv;
 
 
 use getopts::Options;
-use std::{env,fs};
+use std::{env,fs,io};
 use std::error::Error;
 use std::path::Path;
 
@@ -49,8 +49,11 @@ fn print_usage(program: &str, opts: Options) {
 fn search<P: AsRef<Path>> (file_path: &Option<P>, city: &str)
                                  -> Result<Vec<PopulationCount>, Box<Error+Send+Sync>> {
     let mut found = vec![];
-    let file = try!(fs::File::open(file_path));
-    let mut rdr = csv::Reader::from_reader(file);
+    let input: Box<io::Read> = match *file_path {
+        None => Box::new(io::stdin()),
+        Some(ref file_path) => Box::new(try!(fs::File::open(file_path))),
+    };
+    let mut rdr = csv::Reader::from_reader(input);
     for row in rdr.decode::<Row>() {
         let row = row.unwrap();
         match row.population {