refactoring: add interpret function

src/execute.rs

@@ -1,12 +1,29 @@
 use std::{
-    io,
-    process::{Command, Stdio},
+    io::{self},
+    process::{ChildStdout, Command, Stdio},
 };
 
-pub fn execute(command: &str, args: &[&str]) -> io::Result<()> {
-    let mut command = Command::new(command);
-    command.stdout(Stdio::piped()).args(args);
+use crate::parse::parse_line;
+
+pub fn execute<S: Into<Stdio>>(mut command: Command, stdin: S) -> io::Result<(ChildStdout, Stdio)> {
+    command.stdin(stdin);
+    command.stdout(Stdio::piped());
+
     let handle = command.spawn()?;
-    io::copy(&mut handle.stdout.unwrap(), &mut io::stdout())?;
+
+    let stdout = handle.stdout.unwrap();
+    let stderr = match handle.stderr {
+        Some(err) => Stdio::from(err),
+        None => Stdio::null(),
+    };
+    Ok((stdout, stderr))
+}
+
+pub fn interpret(line: &str) -> io::Result<()> {
+    let (command, args) = parse_line(line);
+    let mut command = Command::new(command);
+    command.args(args);
+    let (mut stdout, _) = execute(command, Stdio::null())?;
+    io::copy(&mut stdout, &mut io::stdout())?;
     Ok(())
 }

src/main.rs

@@ -2,8 +2,7 @@ mod execute;
 mod parse;
 mod prompt;
 
-use execute::execute;
-use parse::parse_line;
+use execute::interpret;
 use rustyline::error::ReadlineError;
 use rustyline::{Editor, Result};
 
@@ -19,8 +18,9 @@ fn main() -> Result<()> {
 
         match readline {
             Ok(line) => {
-                let (command, args) = parse_line(&line);
-                execute(command, &args)?;
+                if let Err(err) = interpret(&line) {
+                    println!("{}", err);
+                }
             }
             Err(ReadlineError::Interrupted) => {
                 println!("CTRL-C");