diff --git a/src/env/host.rs b/src/env/host.rs
index acc474f41..736c6bb05 100644
--- a/src/env/host.rs
+++ b/src/env/host.rs
@@ -1,11 +1,16 @@
 pub trait Host {
     fn stdout(&mut self, out: &str);
+    fn stderr(&mut self, out: &str);
 }
 
 impl Host for Box<dyn Host> {
     fn stdout(&mut self, out: &str) {
         (**self).stdout(out)
     }
+
+    fn stderr(&mut self, out: &str) {
+        (**self).stderr(out)
+    }
 }
 
 crate struct BasicHost;
@@ -14,4 +19,8 @@ impl Host for BasicHost {
     fn stdout(&mut self, out: &str) {
         println!("{}", out)
     }
+
+    fn stderr(&mut self, out: &str) {
+        eprintln!("{}", out)
+    }
 }
diff --git a/src/errors.rs b/src/errors.rs
index b4cc52023..e341d4f74 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -21,6 +21,10 @@ impl ShellError {
             error: self.error.copy(),
         }
     }
+
+    crate fn description(&self) -> String {
+        self.title.clone()
+    }
 }
 
 impl std::fmt::Display for ShellError {
diff --git a/src/main.rs b/src/main.rs
index 085cc05f9..733851ebd 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,7 +3,6 @@
 
 #[allow(unused)]
 use crate::prelude::*;
-use std::borrow::Cow::{self, Borrowed, Owned};
 
 mod commands;
 mod context;
@@ -13,6 +12,7 @@ mod format;
 mod object;
 mod parser;
 mod prelude;
+mod shell;
 
 use crate::commands::command::ReturnValue;
 crate use crate::commands::command::{Command, CommandAction, CommandBlueprint};
@@ -21,13 +21,9 @@ crate use crate::env::{Environment, Host};
 crate use crate::errors::ShellError;
 crate use crate::format::{EntriesListView, GenericView};
 use crate::object::Value;
-use rustyline::completion::{Completer, FilenameCompleter, Pair};
-use rustyline::highlight::{Highlighter, MatchingBracketHighlighter};
-use rustyline::hint::{Hinter, HistoryHinter};
 
-use ansi_term::Color;
 use rustyline::error::ReadlineError;
-use rustyline::{ColorMode, Config, Editor, Helper, self};
+use rustyline::{self, ColorMode, Config, Editor};
 use std::collections::VecDeque;
 use std::error::Error;
 use std::sync::{Arc, Mutex};
@@ -48,54 +44,10 @@ impl<T> MaybeOwned<'a, T> {
     }
 }
 
-struct MyHelper(FilenameCompleter, MatchingBracketHighlighter, HistoryHinter);
-impl Completer for MyHelper {
-    type Candidate = Pair;
-
-    fn complete(
-        &self,
-        line: &str,
-        pos: usize,
-        ctx: &rustyline::Context<'_>,
-    ) -> Result<(usize, Vec<Pair>), ReadlineError> {
-        self.0.complete(line, pos, ctx)
-    }
-}
-
-impl Hinter for MyHelper {
-    fn hint(&self, line: &str, pos: usize, ctx: &rustyline::Context<'_>) -> Option<String> {
-        self.2.hint(line, pos, ctx)
-    }
-}
-
-impl Highlighter for MyHelper {
-    fn highlight_prompt<'p>(&self, prompt: &'p str) -> Cow<'p, str> {
-        Owned("\x1b[32m".to_owned() + &prompt[0..prompt.len() - 2] + "\x1b[m> ")
-    }
-
-    fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
-        Owned("\x1b[1m".to_owned() + hint + "\x1b[m")
-    }
-
-    fn highlight<'l>(&self, line: &'l str, pos: usize) -> Cow<'l, str> {
-        self.1.highlight(line, pos)
-    }
-
-    fn highlight_char(&self, line: &str, pos: usize) -> bool {
-        self.1.highlight_char(line, pos)
-    }
-}
-
-impl Helper for MyHelper {}
-
 fn main() -> Result<(), Box<Error>> {
     let config = Config::builder().color_mode(ColorMode::Forced).build();
-    let h = MyHelper(
-        FilenameCompleter::new(),
-        MatchingBracketHighlighter::new(),
-        HistoryHinter {},
-    );
-    let mut rl: Editor<MyHelper> = Editor::with_config(config);
+    let h = crate::shell::Helper::new();
+    let mut rl: Editor<crate::shell::Helper> = Editor::with_config(config);
     rl.set_helper(Some(h));
     if rl.load_history("history.txt").is_err() {
         println!("No previous history.");
@@ -125,48 +77,25 @@ fn main() -> Result<(), Box<Error>> {
             context.lock().unwrap().env.cwd().display().to_string()
         ));
 
-        match readline {
-            Ok(ref line) if line.trim() == "exit" => {
-                break;
-            }
-            Ok(line) => {
-                let result = crate::parser::shell_parser(&line)
-                    .map_err(|e| ShellError::string(format!("{:?}", e)))?;
-
-                let parsed = result.1;
-
+        match process_line(readline, context.clone()) {
+            LineResult::Success(line) => {
                 rl.add_history_entry(line.as_ref());
-
-                let mut input = VecDeque::new();
-
-                for item in parsed {
-                    input = process_command(
-                        crate::parser::print_items(&item),
-                        item.clone(),
-                        input,
-                        context.clone(),
-                    )?;
-                }
-
-                if input.len() > 0 {
-                    if equal_shapes(&input) {
-                        format(crate::commands::to_array(input), context.clone());
-                    } else {
-                        format(input, context.clone());
-                    }
-                }
             }
-            Err(ReadlineError::Interrupted) => {
-                println!("CTRL-C");
+
+            LineResult::Error(err) => {
+                context.lock().unwrap().host.stdout(&err);
+            }
+
+            LineResult::Break => {
                 break;
             }
-            Err(ReadlineError::Eof) => {
-                println!("CTRL-D");
-                break;
-            }
-            Err(err) => {
-                println!("Error: {:?}", err);
-                break;
+
+            LineResult::FatalError(err) => {
+                context
+                    .lock()
+                    .unwrap()
+                    .host
+                    .stdout(&format!("A surprising fatal error occurred.\n{:?}", err));
             }
         }
     }
@@ -175,13 +104,81 @@ fn main() -> Result<(), Box<Error>> {
     Ok(())
 }
 
+enum LineResult {
+    Success(String),
+    Error(String),
+    Break,
+
+    #[allow(unused)]
+    FatalError(ShellError),
+}
+
+fn process_line(
+    readline: Result<String, ReadlineError>,
+    context: Arc<Mutex<Context>>,
+) -> LineResult {
+    match &readline {
+        Ok(line) if line.trim() == "exit" => LineResult::Break,
+
+        Ok(line) if line.trim() == "" => LineResult::Success(line.clone()),
+
+        Ok(line) => {
+            let result = match crate::parser::shell_parser(&line) {
+                Err(err) => {
+                    return LineResult::Error(format!("{:?}", err));
+                }
+
+                Ok(val) => val,
+            };
+
+            let parsed = result.1;
+
+            let mut input = VecDeque::new();
+
+            for item in parsed {
+                input = match process_command(
+                    crate::parser::print_items(&item),
+                    item.clone(),
+                    input,
+                    context.clone(),
+                ) {
+                    Ok(val) => val,
+                    Err(err) => return LineResult::Error(format!("{}", err.description())),
+                };
+            }
+
+            if input.len() > 0 {
+                if equal_shapes(&input) {
+                    format(crate::commands::to_array(input), context.clone());
+                } else {
+                    format(input, context.clone());
+                }
+            }
+
+            LineResult::Success(line.to_string())
+        }
+        Err(ReadlineError::Interrupted) => {
+            println!("CTRL-C");
+            LineResult::Break
+        }
+        Err(ReadlineError::Eof) => {
+            println!("CTRL-D");
+            LineResult::Break
+        }
+        Err(err) => {
+            println!("Error: {:?}", err);
+            LineResult::Break
+        }
+    }
+}
+
 fn process_command(
     line: String,
     parsed: Vec<crate::parser::Item>,
     input: VecDeque<Value>,
     context: Arc<Mutex<Context>>,
 ) -> Result<VecDeque<Value>, ShellError> {
-    let command = &parsed[0].name();
+    let command = &parsed[0].name()?;
     let arg_list = parsed[1..].iter().map(|i| i.as_value()).collect();
 
     if command == &"format" {
diff --git a/src/object/base.rs b/src/object/base.rs
index 3720407ca..63615814f 100644
--- a/src/object/base.rs
+++ b/src/object/base.rs
@@ -120,6 +120,7 @@ impl Value {
         }
     }
 
+    #[allow(unused)]
     crate fn as_bool(&self) -> Result<bool, ShellError> {
         match self {
             Value::Primitive(Primitive::Boolean(b)) => Ok(*b),
@@ -143,6 +144,7 @@ impl Value {
         Value::Primitive(Primitive::Int(s.into()))
     }
 
+    #[allow(unused)]
     crate fn bool(s: impl Into<bool>) -> Value {
         Value::Primitive(Primitive::Boolean(s.into()))
     }
@@ -213,74 +215,34 @@ crate fn find(obj: &Value, field: &str, op: &str, rhs: &Value) -> bool {
             //println!("'{:?}' '{}' '{:?}'", v, op, rhs);
 
             match v {
-                Value::Primitive(Primitive::Boolean(b)) => {
-                    match (op, rhs) {
-                        ("-eq", Value::Primitive(Primitive::Boolean(b2))) => {
-                            b == *b2
-                        }
-                        ("-ne", Value::Primitive(Primitive::Boolean(b2))) => {
-                            b != *b2
-                        }
-                        _ => false
-                    }
-                }
-                Value::Primitive(Primitive::Bytes(i)) => {
-                    match (op, rhs) {
-                        ("-lt", Value::Primitive(Primitive::Int(i2))) => {
-                            i < (*i2 as u128)
-                        }
-                        ("-gt", Value::Primitive(Primitive::Int(i2))) => {
-                            i > (*i2 as u128)
-                        }
-                        ("-le", Value::Primitive(Primitive::Int(i2))) => {
-                            i <= (*i2 as u128)
-                        }
-                        ("-ge", Value::Primitive(Primitive::Int(i2))) => {
-                            i >= (*i2 as u128)
-                        }
-                        ("-eq", Value::Primitive(Primitive::Int(i2))) => {
-                            i == (*i2 as u128)
-                        }
-                        ("-ne", Value::Primitive(Primitive::Int(i2))) => {
-                            i != (*i2 as u128)
-                        }
-                        _ => false
-                    }
-                }
-                Value::Primitive(Primitive::Int(i)) => {
-                    match (op, rhs) {
-                        ("-lt", Value::Primitive(Primitive::Int(i2))) => {
-                            i < *i2
-                        }
-                        ("-gt", Value::Primitive(Primitive::Int(i2))) => {
-                            i > *i2
-                        }
-                        ("-le", Value::Primitive(Primitive::Int(i2))) => {
-                            i <= *i2
-                        }
-                        ("-ge", Value::Primitive(Primitive::Int(i2))) => {
-                            i >= *i2
-                        }
-                        ("-eq", Value::Primitive(Primitive::Int(i2))) => {
-                            i == *i2
-                        }
-                        ("-ne", Value::Primitive(Primitive::Int(i2))) => {
-                            i != *i2
-                        }
-                        _ => false
-                    }
-                }
-                Value::Primitive(Primitive::String(s)) => {
-                    match (op, rhs) {
-                        ("-eq", Value::Primitive(Primitive::String(s2))) => {
-                            s == *s2
-                        }
-                        ("-ne", Value::Primitive(Primitive::String(s2))) => {
-                            s != *s2
-                        }
-                        _ => false
-                    }
-                }
+                Value::Primitive(Primitive::Boolean(b)) => match (op, rhs) {
+                    ("-eq", Value::Primitive(Primitive::Boolean(b2))) => b == *b2,
+                    ("-ne", Value::Primitive(Primitive::Boolean(b2))) => b != *b2,
+                    _ => false,
+                },
+                Value::Primitive(Primitive::Bytes(i)) => match (op, rhs) {
+                    ("-lt", Value::Primitive(Primitive::Int(i2))) => i < (*i2 as u128),
+                    ("-gt", Value::Primitive(Primitive::Int(i2))) => i > (*i2 as u128),
+                    ("-le", Value::Primitive(Primitive::Int(i2))) => i <= (*i2 as u128),
+                    ("-ge", Value::Primitive(Primitive::Int(i2))) => i >= (*i2 as u128),
+                    ("-eq", Value::Primitive(Primitive::Int(i2))) => i == (*i2 as u128),
+                    ("-ne", Value::Primitive(Primitive::Int(i2))) => i != (*i2 as u128),
+                    _ => false,
+                },
+                Value::Primitive(Primitive::Int(i)) => match (op, rhs) {
+                    ("-lt", Value::Primitive(Primitive::Int(i2))) => i < *i2,
+                    ("-gt", Value::Primitive(Primitive::Int(i2))) => i > *i2,
+                    ("-le", Value::Primitive(Primitive::Int(i2))) => i <= *i2,
+                    ("-ge", Value::Primitive(Primitive::Int(i2))) => i >= *i2,
+                    ("-eq", Value::Primitive(Primitive::Int(i2))) => i == *i2,
+                    ("-ne", Value::Primitive(Primitive::Int(i2))) => i != *i2,
+                    _ => false,
+                },
+                Value::Primitive(Primitive::String(s)) => match (op, rhs) {
+                    ("-eq", Value::Primitive(Primitive::String(s2))) => s == *s2,
+                    ("-ne", Value::Primitive(Primitive::String(s2))) => s != *s2,
+                    _ => false,
+                },
                 _ => false,
             }
         }
diff --git a/src/parser/parse.rs b/src/parser/parse.rs
index 40e40198e..276c057a3 100644
--- a/src/parser/parse.rs
+++ b/src/parser/parse.rs
@@ -39,11 +39,12 @@ crate fn print_items(items: &[Item]) -> String {
 }
 
 impl Item {
-    crate fn name(&self) -> &str {
+    crate fn name(&self) -> Result<&str, ShellError> {
         match self {
-            Item::Quoted(s) => s,
-            Item::Bare(s) => s,
-            Item::Boolean(_) | Item::Int(_) => unimplemented!(),
+            Item::Quoted(s) => Ok(s),
+            Item::Bare(s) => Ok(s),
+            Item::Boolean(i) => Err(ShellError::string(format!("{} is not a valid command", i))),
+            Item::Int(i) => Err(ShellError::string(format!("{} is not a valid command", i))),
         }
     }
 }
diff --git a/src/shell.rs b/src/shell.rs
new file mode 100644
index 000000000..7a87fa0a9
--- /dev/null
+++ b/src/shell.rs
@@ -0,0 +1,4 @@
+crate mod completer;
+crate mod helper;
+
+crate use helper::Helper;
diff --git a/src/shell/completer.rs b/src/shell/completer.rs
new file mode 100644
index 000000000..0f68b3354
--- /dev/null
+++ b/src/shell/completer.rs
@@ -0,0 +1,41 @@
+use rustyline::completion::{Candidate, Completer};
+use rustyline::line_buffer::LineBuffer;
+
+#[derive(Debug)]
+crate struct NuCompleter;
+
+impl Completer for NuCompleter {
+    type Candidate = NuPair;
+
+    fn complete(
+        &self,
+        _line: &str,
+        _pos: usize,
+        _context: &rustyline::Context,
+    ) -> rustyline::Result<(usize, Vec<NuPair>)> {
+        Ok((
+            0,
+            vec![
+                NuPair("exit", "exit"),
+                NuPair("ls", "ls"),
+                NuPair("ps", "ps"),
+            ],
+        ))
+    }
+
+    fn update(&self, line: &mut LineBuffer, start: usize, elected: &str) {
+        let end = line.pos();
+        line.replace(start..end, elected)
+    }
+}
+
+crate struct NuPair(&'static str, &'static str);
+
+impl Candidate for NuPair {
+    fn display(&self) -> &str {
+        self.0
+    }
+    fn replacement(&self) -> &str {
+        self.1
+    }
+}
diff --git a/src/shell/helper.rs b/src/shell/helper.rs
new file mode 100644
index 000000000..aaa5bd9f3
--- /dev/null
+++ b/src/shell/helper.rs
@@ -0,0 +1,62 @@
+use crate::shell::completer::{NuCompleter, NuPair};
+
+use rustyline::completion::Completer;
+use rustyline::error::ReadlineError;
+use rustyline::highlight::{Highlighter, MatchingBracketHighlighter};
+use rustyline::hint::{Hinter, HistoryHinter};
+use std::borrow::Cow::{self, Owned};
+
+crate struct Helper {
+    completer: NuCompleter,
+    highlighter: MatchingBracketHighlighter,
+    hinter: HistoryHinter,
+}
+
+impl Helper {
+    crate fn new() -> Helper {
+        Helper {
+            completer: NuCompleter,
+            highlighter: MatchingBracketHighlighter::new(),
+            hinter: HistoryHinter {},
+        }
+    }
+}
+
+impl Completer for Helper {
+    type Candidate = NuPair;
+
+    fn complete(
+        &self,
+        line: &str,
+        pos: usize,
+        ctx: &rustyline::Context<'_>,
+    ) -> Result<(usize, Vec<NuPair>), ReadlineError> {
+        self.completer.complete(line, pos, ctx)
+    }
+}
+
+impl Hinter for Helper {
+    fn hint(&self, line: &str, pos: usize, ctx: &rustyline::Context<'_>) -> Option<String> {
+        self.hinter.hint(line, pos, ctx)
+    }
+}
+
+impl Highlighter for Helper {
+    fn highlight_prompt<'p>(&self, prompt: &'p str) -> Cow<'p, str> {
+        Owned("\x1b[32m".to_owned() + &prompt[0..prompt.len() - 2] + "\x1b[m> ")
+    }
+
+    fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
+        Owned("\x1b[1m".to_owned() + hint + "\x1b[m")
+    }
+
+    fn highlight<'l>(&self, line: &'l str, pos: usize) -> Cow<'l, str> {
+        self.highlighter.highlight(line, pos)
+    }
+
+    fn highlight_char(&self, line: &str, pos: usize) -> bool {
+        self.highlighter.highlight_char(line, pos)
+    }
+}
+
+impl rustyline::Helper for Helper {}