Unknown Command and cargo doc now working

hw7/task2/Cargo.toml

 
 [dependencies]
 nix = "0.9.0"
+
+[[bin]]
+doc = false
+name = "task2"

hw7/task2/src/lib.rs

     pub fn prompt(&mut self) -> Result<Option<String>, ErrorType> {
         match env::current_dir() {
             Ok(pwd) => {
-                let _ = self.writer.write(
-                    format!("{} {} > ", self.name, pwd.display())
+                let _ = self.writer.write_all(
+                    format!("{} {}> ", self.name, pwd.display())
                         .as_bytes(),
                 );
                 let _ = self.writer.flush();
     }
 
     /// Runs a command.
-    /// Currently only `cd` and `exit` are working.
     fn run(&mut self, command: Command) -> Result<(), ErrorType> {
 
         match command {
         Ok(())
     }
 
-    fn execute(&self, cmd: &str) {
+    fn execute(&mut self, cmd: &str) {
         let parts: Vec<&str> = cmd.split_whitespace().collect();
         let args: Vec<CString> = parts.iter().map(|f| CString::new(*f).unwrap()).collect();
+        let cmd = args.clone();
         let t = args.into_boxed_slice();
 
-        execvp(&t[0], &t).unwrap();
+        match execvp(&t[0], &t) {
+            Ok(_) => {},
+            Err(_) => {
+                let _ = self.writer.write_all(
+                    format!("{:?}: command not found\n", cmd[0]).as_bytes());
+            },
+        }
     }
 }