cat(1): working implementation

src/cat.rs

@@ -18,9 +18,10 @@
  */
 
 use std::env;
-use std::fs::{File, read_to_string};
+use std::fs::{ File, read_to_string };
+use std::os::fd::{ AsRawFd, FromRawFd };
 use std::io;
-use std::io::{ BufRead, Read };
+use std::io::{ BufRead, Read, Write };
 use std::str;
 
 use arg::Args;
@@ -46,42 +47,39 @@ fn main() -> ExitCode {
   ).unwrap();
 
   let argv0 = args.argv0;
-
   let mut output = String::new();
+  let stdin = io::stdin();
 
   if args.paths.is_empty() { args.paths.push("-".to_string()); }
  
-  while args.u {
-    for path in &args.paths {
+  if args.u {
+    for path in args.paths {
+      let handle: File;
       if path == "-" {
-        loop {
-          let mut buf = String::new();
-          match io::stdin().lock().read_line(&mut buf) {
-            Ok(bytes) => {
-              if bytes == 0 { break };
-              print!("{}", buf);
-            },
-            Err(err) => println!("{}", err),
-          };
+        handle = unsafe {
+          File::from_raw_fd(stdin.as_raw_fd())
         }
       } else {
-        let mut input = String::new();
-        match File::open(path) {
-          Ok(input) => {},
+        handle = match File::open(&path) {
+          Ok(file) => file,
           Err(_) => {
-            println!("{}: {}: No such file or directory.", &argv0, path);
+            eprintln!("{}: {}: No such file or directory.", &argv0, &path);
             return ExitCode::NoInput;
           },
         };
       }
-    }
-    return ExitCode::Ok;
-  }
+      let mut stdout = io::BufWriter::with_capacity(0, io::stdout());
 
+      for byte in handle.bytes() {
+        stdout.write(&[byte.unwrap()]).unwrap();
+        stdout.flush().unwrap();
+      }
+    } return ExitCode::Ok;
+  } else {
     for path in args.paths {
       if path == "-" {
         let mut bytes: Vec<u8> = Vec::new();
-      io::stdin().lock().read_to_end(&mut bytes).unwrap();
+        stdin.lock().read_to_end(&mut bytes).unwrap();
 
         for byte in &bytes {
           output.push_str(str::from_utf8(&[byte.to_owned()]).unwrap());
@@ -98,5 +96,6 @@ fn main() -> ExitCode {
       print!("{}", output);
       output.clear();
     }
+  }
   ExitCode::Ok
 }