Update file-io.md (#561)

remove unless mut.
rustcc · Jan 26, 2018 · 2755188 · 2755188
1 parent 7bedfac
commit 2755188
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/io/file-io.md b/io/file-io.md
@@ -15,9 +15,9 @@ fn create_file(filename: &str, buf: &[u8]) -> io::Result<()> {
 }
 
 // read from file to String
-fn read_file(filename: &str, mut buf: &mut String) -> io::Result<()> {
+fn read_file(filename: &str, buf: &mut String) -> io::Result<()> {
 	let mut f = try!(File::open(filename));
-	try!(f.read_to_string(&mut buf));
+	try!(f.read_to_string(&buf));
 	Ok(())
 }