diff --git a/rustfmt.toml b/rustfmt.toml
new file mode 100644
index 0000000000..c51666e8f4
--- /dev/null
+++ b/rustfmt.toml
@@ -0,0 +1 @@
+edition = "2018"
\ No newline at end of file
diff --git a/src/cli.rs b/src/cli.rs
index bc16001036..afa320e3c8 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -1,12 +1,11 @@
 use crate::prelude::*;
 
 use crate::commands::classified::{ClassifiedCommand, ExternalCommand, InternalCommand};
-use crate::commands::command::ReturnValue;
 use crate::context::Context;
-crate use crate::env::Host;
 crate use crate::errors::ShellError;
 crate use crate::format::{EntriesListView, GenericView};
 use crate::object::Value;
+use crate::stream::empty_stream;
 
 use rustyline::error::ReadlineError;
 use rustyline::{self, ColorMode, Config, Editor};
@@ -29,7 +28,7 @@ impl<T> MaybeOwned<'a, T> {
     }
 }
 
-pub fn cli() -> Result<(), Box<Error>> {
+pub async fn cli() -> Result<(), Box<Error>> {
     let config = Config::builder().color_mode(ColorMode::Forced).build();
     let h = crate::shell::Helper::new();
     let mut rl: Editor<crate::shell::Helper> = Editor::with_config(config);
@@ -50,8 +49,6 @@ pub fn cli() -> Result<(), Box<Error>> {
         use crate::commands::*;
 
         context.add_commands(vec![
-            ("format", Arc::new(format)),
-            ("format-list", Arc::new(format_list)),
             ("ps", Arc::new(ps::ps)),
             ("ls", Arc::new(ls::ls)),
             ("cd", Arc::new(cd::cd)),
@@ -67,15 +64,18 @@ pub fn cli() -> Result<(), Box<Error>> {
     }
 
     loop {
-        let readline = rl.readline(&format!("{}> ", context.env.cwd().display().to_string()));
+        let readline = rl.readline(&format!(
+            "{}> ",
+            context.env.lock().unwrap().cwd().display().to_string()
+        ));
 
-        match process_line(readline, &mut context) {
+        match process_line(readline, &mut context).await {
             LineResult::Success(line) => {
                 rl.add_history_entry(line.clone());
             }
 
             LineResult::Error(err) => {
-                context.host.stdout(&err);
+                context.host.lock().unwrap().stdout(&err);
             }
 
             LineResult::Break => {
@@ -85,6 +85,8 @@ pub fn cli() -> Result<(), Box<Error>> {
             LineResult::FatalError(err) => {
                 context
                     .host
+                    .lock()
+                    .unwrap()
                     .stdout(&format!("A surprising fatal error occurred.\n{:?}", err));
             }
         }
@@ -103,7 +105,7 @@ enum LineResult {
     FatalError(ShellError),
 }
 
-fn process_line(readline: Result<String, ReadlineError>, ctx: &mut Context) -> LineResult {
+async fn process_line(readline: Result<String, ReadlineError>, ctx: &mut Context) -> LineResult {
     match &readline {
         Ok(line) if line.trim() == "exit" => LineResult::Break,
 
@@ -120,29 +122,25 @@ fn process_line(readline: Result<String, ReadlineError>, ctx: &mut Context) -> L
 
             let parsed = result.1;
 
-            let mut input = VecDeque::new();
+            let mut input: InputStream = VecDeque::new().boxed();
 
             for item in parsed {
-                input = match process_command(item.clone(), input, ctx) {
+                input = match process_command(item.clone(), input, ctx).await {
                     Ok(val) => val,
                     Err(err) => return LineResult::Error(format!("{}", err.description())),
                 };
             }
 
-            if input.len() > 0 {
-                if equal_shapes(&input) {
-                    let array = crate::commands::stream_to_array(input);
+            let input_vec: VecDeque<_> = input.collect().await;
+
+            if input_vec.len() > 0 {
+                if equal_shapes(&input_vec) {
+                    let array = crate::commands::stream_to_array(input_vec.boxed()).await;
                     let args = CommandArgs::from_context(ctx, vec![], array);
-                    match format(args) {
-                        Ok(_) => {}
-                        Err(err) => return LineResult::Error(err.to_string()),
-                    }
+                    format(args).await;
                 } else {
-                    let args = CommandArgs::from_context(ctx, vec![], input);
-                    match format(args) {
-                        Ok(_) => {}
-                        Err(err) => return LineResult::Error(err.to_string()),
-                    }
+                    let args = CommandArgs::from_context(ctx, vec![], input_vec.boxed());
+                    format(args).await;
                 }
             }
 
@@ -163,14 +161,14 @@ fn process_line(readline: Result<String, ReadlineError>, ctx: &mut Context) -> L
     }
 }
 
-fn process_command(
+async fn process_command(
     parsed: Vec<crate::parser::Item>,
-    input: VecDeque<Value>,
+    input: InputStream,
     context: &mut Context,
-) -> Result<VecDeque<Value>, ShellError> {
+) -> Result<InputStream, ShellError> {
     let command = classify_command(&parsed, context)?;
 
-    command.run(input, context)
+    command.run(input, context).await
 }
 
 fn classify_command(
@@ -199,25 +197,26 @@ fn classify_command(
     }
 }
 
-fn format(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
-    let last = args.input.len() - 1;
-    for (i, item) in args.input.iter().enumerate() {
+async fn format(args: CommandArgs) -> OutputStream {
+    let input: Vec<_> = args.input.collect().await;
+    let last = input.len() - 1;
+    for (i, item) in input.iter().enumerate() {
         let view = GenericView::new(item);
-        crate::format::print_view(&view, args.host);
+        crate::format::print_view(&view, &mut *args.host.lock().unwrap());
 
         if last != i {
             println!("");
         }
     }
 
-    Ok(VecDeque::new())
+    empty_stream()
 }
 
-fn format_list(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
-    let view = EntriesListView::from_stream(args.input);
-    crate::format::print_view(&view, args.host);
+async fn format_list(args: CommandArgs) -> OutputStream {
+    let view = EntriesListView::from_stream(args.input).await;
+    crate::format::print_view(&view, &mut *args.host.lock().unwrap());
 
-    Ok(VecDeque::new())
+    empty_stream()
 }
 
 fn equal_shapes(input: &VecDeque<Value>) -> bool {
diff --git a/src/commands/cd.rs b/src/commands/cd.rs
index a4f6523427..ab2f59b314 100644
--- a/src/commands/cd.rs
+++ b/src/commands/cd.rs
@@ -2,18 +2,18 @@ use crate::errors::ShellError;
 use crate::prelude::*;
 use std::env;
 
-pub fn cd(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn cd(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let target = match args.args.first() {
         // TODO: This needs better infra
         None => return Err(ShellError::string(format!("cd must take one arg"))),
         Some(v) => v.as_string()?.clone(),
     };
 
-    let cwd = args.env.cwd().to_path_buf();
+    let cwd = args.env.lock().unwrap().cwd().to_path_buf();
 
     let mut stream = VecDeque::new();
     let path = dunce::canonicalize(cwd.join(&target).as_path())?;
     let _ = env::set_current_dir(&path);
     stream.push_back(ReturnValue::change_cwd(path));
-    Ok(stream)
+    Ok(stream.boxed())
 }
diff --git a/src/commands/classified.rs b/src/commands/classified.rs
index 36a23ce6dd..a528b9bd34 100644
--- a/src/commands/classified.rs
+++ b/src/commands/classified.rs
@@ -8,37 +8,38 @@ crate enum ClassifiedCommand {
 }
 
 impl ClassifiedCommand {
-    crate fn run(
+    crate async fn run(
         self,
-        input: VecDeque<Value>,
+        input: InputStream,
         context: &mut Context,
-    ) -> Result<VecDeque<Value>, ShellError> {
+    ) -> Result<InputStream, ShellError> {
         match self {
             ClassifiedCommand::Internal(internal) => {
                 let result = context.run_command(internal.command, internal.args, input)?;
+                let env = context.env.clone();
 
-                let mut next = VecDeque::new();
+                let stream = result.filter_map(move |v| match v {
+                    ReturnValue::Action(action) => match action {
+                        CommandAction::ChangeCwd(cwd) => {
+                            env.lock().unwrap().cwd = cwd;
+                            futures::future::ready(None)
+                        }
+                    },
 
-                for v in result {
-                    match v {
-                        ReturnValue::Action(action) => match action {
-                            CommandAction::ChangeCwd(cwd) => context.env.cwd = cwd,
-                        },
+                    ReturnValue::Value(v) => futures::future::ready(Some(v)),
+                });
 
-                        ReturnValue::Value(v) => next.push_back(v),
-                    }
-                }
-
-                Ok(next)
+                Ok(stream.boxed() as InputStream)
             }
 
             ClassifiedCommand::External(external) => {
                 Exec::shell(&external.name)
                     .args(&external.args)
-                    .cwd(context.env.cwd())
+                    .cwd(context.env.lock().unwrap().cwd())
                     .join()
                     .unwrap();
-                Ok(VecDeque::new())
+
+                Ok(VecDeque::new().boxed() as InputStream)
             }
         }
     }
diff --git a/src/commands/command.rs b/src/commands/command.rs
index d48adab03e..71479ceb0f 100644
--- a/src/commands/command.rs
+++ b/src/commands/command.rs
@@ -3,22 +3,22 @@ use crate::object::Value;
 use crate::prelude::*;
 use std::path::PathBuf;
 
-pub struct CommandArgs<'caller> {
-    pub host: &'caller mut dyn Host,
-    pub env: &'caller Environment,
+pub struct CommandArgs {
+    pub host: Arc<Mutex<dyn Host>>,
+    pub env: Arc<Mutex<Environment>>,
     pub args: Vec<Value>,
-    pub input: VecDeque<Value>,
+    pub input: InputStream,
 }
 
-impl CommandArgs<'caller> {
+impl CommandArgs {
     crate fn from_context(
         ctx: &'caller mut Context,
         args: Vec<Value>,
-        input: VecDeque<Value>,
-    ) -> CommandArgs<'caller> {
+        input: InputStream,
+    ) -> CommandArgs {
         CommandArgs {
-            host: &mut ctx.host,
-            env: &ctx.env,
+            host: ctx.host.clone(),
+            env: ctx.env.clone(),
             args,
             input,
         }
@@ -49,14 +49,14 @@ impl ReturnValue {
 }
 
 pub trait Command {
-    fn run(&self, args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError>;
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError>;
 }
 
 impl<F> Command for F
 where
-    F: Fn(CommandArgs<'_>) -> Result<VecDeque<ReturnValue>, ShellError>,
+    F: Fn(CommandArgs) -> Result<OutputStream, ShellError>,
 {
-    fn run(&self, args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
         self(args)
     }
 }
diff --git a/src/commands/ls.rs b/src/commands/ls.rs
index b591bdc02b..8b07c90af4 100644
--- a/src/commands/ls.rs
+++ b/src/commands/ls.rs
@@ -2,8 +2,8 @@ use crate::errors::ShellError;
 use crate::object::{dir_entry_dict, Value};
 use crate::prelude::*;
 
-pub fn ls(args: CommandArgs<'value>) -> Result<VecDeque<ReturnValue>, ShellError> {
-    let cwd = args.env.cwd().to_path_buf();
+pub fn ls(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let cwd = args.env.lock().unwrap().cwd().to_path_buf();
 
     let entries = std::fs::read_dir(&cwd).map_err(|e| ShellError::string(format!("{:?}", e)))?;
 
@@ -14,5 +14,5 @@ pub fn ls(args: CommandArgs<'value>) -> Result<VecDeque<ReturnValue>, ShellError
         shell_entries.push_back(ReturnValue::Value(value))
     }
 
-    Ok(shell_entries)
+    Ok(shell_entries.boxed())
 }
diff --git a/src/commands/ps.rs b/src/commands/ps.rs
index 8e34dab582..dcd61b9b2e 100644
--- a/src/commands/ps.rs
+++ b/src/commands/ps.rs
@@ -4,7 +4,7 @@ use crate::object::Value;
 use crate::prelude::*;
 use sysinfo::SystemExt;
 
-pub fn ps(_args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn ps(_args: CommandArgs) -> Result<OutputStream, ShellError> {
     let mut system = sysinfo::System::new();
     system.refresh_all();
 
@@ -15,5 +15,5 @@ pub fn ps(_args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellErr
         .map(|(_, process)| ReturnValue::Value(Value::Object(process_dict(process))))
         .collect::<VecDeque<_>>();
 
-    Ok(list)
+    Ok(list.boxed())
 }
diff --git a/src/commands/reject.rs b/src/commands/reject.rs
index c7ab2b0142..ef8313ff7b 100644
--- a/src/commands/reject.rs
+++ b/src/commands/reject.rs
@@ -3,7 +3,7 @@ use crate::object::base::reject_fields;
 use crate::object::Value;
 use crate::prelude::*;
 
-pub fn reject(args: CommandArgs<'value>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn reject(args: CommandArgs) -> Result<OutputStream, ShellError> {
     if args.args.is_empty() {
         return Err(ShellError::string("select requires a field"));
     }
@@ -11,12 +11,10 @@ pub fn reject(args: CommandArgs<'value>) -> Result<VecDeque<ReturnValue>, ShellE
     let fields: Result<Vec<String>, _> = args.args.iter().map(|a| a.as_string()).collect();
     let fields = fields?;
 
-    let objects = args
+    let stream = args
         .input
-        .iter()
-        .map(|item| Value::Object(reject_fields(item, &fields)))
-        .map(|item| ReturnValue::Value(item))
-        .collect();
+        .map(move |item| Value::Object(reject_fields(&item, &fields)))
+        .map(|item| ReturnValue::Value(item));
 
-    Ok(objects)
+    Ok(stream.boxed())
 }
diff --git a/src/commands/select.rs b/src/commands/select.rs
index 6e346ed567..3703c6217a 100644
--- a/src/commands/select.rs
+++ b/src/commands/select.rs
@@ -3,7 +3,7 @@ use crate::object::base::select_fields;
 use crate::object::Value;
 use crate::prelude::*;
 
-pub fn select(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn select(args: CommandArgs) -> Result<OutputStream, ShellError> {
     if args.args.is_empty() {
         return Err(ShellError::string("select requires a field"));
     }
@@ -13,10 +13,9 @@ pub fn select(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, Shell
 
     let objects = args
         .input
-        .iter()
-        .map(|item| Value::Object(select_fields(item, &fields)))
-        .map(|item| ReturnValue::Value(item))
-        .collect();
+        .map(move |item| Value::Object(select_fields(&item, &fields)))
+        .map(|item| ReturnValue::Value(item));
 
-    Ok(objects)
+    let stream = Pin::new(Box::new(objects));
+    Ok(stream)
 }
diff --git a/src/commands/skip.rs b/src/commands/skip.rs
index f1059adce7..0ff5ca1267 100644
--- a/src/commands/skip.rs
+++ b/src/commands/skip.rs
@@ -1,21 +1,13 @@
 use crate::errors::ShellError;
 use crate::prelude::*;
 
-pub fn skip(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn skip(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let amount = args.args[0].as_int()?;
 
-    let amount = if args.input.len() > amount as usize {
-        amount as usize
-    } else {
-        args.input.len()
-    };
+    let input = args.input;
 
-    let out: VecDeque<ReturnValue> = args
-        .input
-        .into_iter()
-        .skip(amount)
+    Ok(input
+        .skip(amount as u64)
         .map(|v| ReturnValue::Value(v))
-        .collect();
-
-    Ok(out)
+        .boxed())
 }
diff --git a/src/commands/sort_by.rs b/src/commands/sort_by.rs
index 0f289fdfdf..13663d88a1 100644
--- a/src/commands/sort_by.rs
+++ b/src/commands/sort_by.rs
@@ -1,23 +1,26 @@
 use crate::errors::ShellError;
 use crate::prelude::*;
+use futures::stream::BoxStream;
 
-pub fn sort_by(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn sort_by(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let fields: Result<Vec<_>, _> = args.args.iter().map(|a| a.as_string()).collect();
     let fields = fields?;
 
-    let mut output = args.input.into_iter().collect::<Vec<_>>();
+    let output = args.input.collect::<Vec<_>>();
 
-    output.sort_by_key(|item| {
-        fields
-            .iter()
-            .map(|f| item.get_data_by_key(f).borrow().copy())
-            .collect::<Vec<Value>>()
+    let output = output.map(move |mut vec| {
+        vec.sort_by_key(|item| {
+            fields
+                .iter()
+                .map(|f| item.get_data_by_key(f).borrow().copy())
+                .collect::<Vec<Value>>()
+        });
+
+        vec.into_iter()
+            .map(|v| ReturnValue::Value(v.copy()))
+            .collect::<VecDeque<_>>()
+            .boxed()
     });
 
-    let output = output
-        .iter()
-        .map(|o| ReturnValue::Value(o.copy()))
-        .collect();
-
-    Ok(output)
+    Ok(output.flatten_stream().boxed())
 }
diff --git a/src/commands/take.rs b/src/commands/take.rs
index 540ec4204d..2352f16b2f 100644
--- a/src/commands/take.rs
+++ b/src/commands/take.rs
@@ -3,21 +3,13 @@ use crate::prelude::*;
 
 // TODO: "Amount remaining" wrapper
 
-pub fn take(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn take(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let amount = args.args[0].as_int()?;
 
-    let amount = if args.input.len() > amount as usize {
-        amount as usize
-    } else {
-        args.input.len()
-    };
+    let input = args.input;
 
-    let out: VecDeque<ReturnValue> = args
-        .input
-        .into_iter()
-        .take(amount)
+    Ok(input
+        .take(amount as u64)
         .map(|v| ReturnValue::Value(v))
-        .collect();
-
-    Ok(out)
+        .boxed())
 }
diff --git a/src/commands/to_array.rs b/src/commands/to_array.rs
index 6ae59714d5..93a0272973 100644
--- a/src/commands/to_array.rs
+++ b/src/commands/to_array.rs
@@ -1,15 +1,17 @@
-use crate::errors::ShellError;
 use crate::object::Value;
 use crate::prelude::*;
 
-pub fn to_array(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
-    let out = args.input.into_iter().collect();
-    Ok(ReturnValue::single(Value::List(out)))
+pub fn to_array(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let out = args.input.collect();
+    Ok(out
+        .map(|vec: Vec<_>| single_output(Value::List(vec)))
+        .flatten_stream()
+        .boxed())
 }
 
-crate fn stream_to_array(stream: VecDeque<Value>) -> VecDeque<Value> {
-    let out = Value::List(stream.into_iter().collect());
+crate async fn stream_to_array(stream: InputStream) -> InputStream {
+    let out = Value::List(stream.collect().await);
     let mut stream = VecDeque::new();
     stream.push_back(out);
-    stream
+    stream.boxed() as InputStream
 }
diff --git a/src/commands/view.rs b/src/commands/view.rs
index 728fa93623..0c6b5526a5 100644
--- a/src/commands/view.rs
+++ b/src/commands/view.rs
@@ -2,14 +2,14 @@ use crate::errors::ShellError;
 use crate::prelude::*;
 use prettyprint::PrettyPrinter;
 
-pub fn view(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn view(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let target = match args.args.first() {
         // TODO: This needs better infra
         None => return Err(ShellError::string(format!("cat must take one arg"))),
         Some(v) => v.as_string()?.clone(),
     };
 
-    let cwd = args.env.cwd().to_path_buf();
+    let cwd = args.env.lock().unwrap().cwd().to_path_buf();
 
     let printer = PrettyPrinter::default()
         .line_numbers(false)
@@ -22,5 +22,5 @@ pub fn view(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellEr
 
     let _ = printer.file(file.display().to_string());
 
-    Ok(VecDeque::new())
+    Ok(VecDeque::new().boxed())
 }
diff --git a/src/commands/where_.rs b/src/commands/where_.rs
index 17f53e61bc..3db875f756 100644
--- a/src/commands/where_.rs
+++ b/src/commands/where_.rs
@@ -2,26 +2,27 @@ use crate::errors::ShellError;
 use crate::object::base::find;
 use crate::prelude::*;
 
-pub fn r#where(args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
+pub fn r#where(args: CommandArgs) -> Result<OutputStream, ShellError> {
     if args.args.is_empty() {
         return Err(ShellError::string("select requires a field"));
     }
 
     let field: Result<String, _> = args.args[0].as_string();
     let field = field?;
+    let input = args.input;
+    let operator = args.args[1].copy();
 
-    match args.args[1] {
-        Value::Primitive(Primitive::Operator(ref operator)) => {
-            let objects = args
-                .input
-                .iter()
-                .filter(|item| find(&item, &field, operator, &args.args[2]))
-                .map(|item| ReturnValue::Value(item.copy()))
-                .collect();
+    match operator {
+        Value::Primitive(Primitive::Operator(operator)) => {
+            let right = args.args[2].copy();
 
-            Ok(objects)
+            let objects = input
+                .filter(move |item| futures::future::ready(find(&item, &field, &operator, &right)))
+                .map(|item| ReturnValue::Value(item.copy()));
+
+            Ok(objects.boxed())
         }
-        ref x => {
+        x => {
             println!("{:?}", x);
             Err(ShellError::string("expected a comparison operator"))
         }
diff --git a/src/context.rs b/src/context.rs
index bcbb30afcc..6f49f6b279 100644
--- a/src/context.rs
+++ b/src/context.rs
@@ -5,16 +5,16 @@ use std::sync::Arc;
 
 pub struct Context {
     commands: indexmap::IndexMap<String, Arc<dyn Command>>,
-    crate host: Box<dyn Host>,
-    crate env: Environment,
+    crate host: Arc<Mutex<dyn Host>>,
+    crate env: Arc<Mutex<Environment>>,
 }
 
 impl Context {
     crate fn basic() -> Result<Context, Box<Error>> {
         Ok(Context {
             commands: indexmap::IndexMap::new(),
-            host: Box::new(crate::env::host::BasicHost),
-            env: Environment::basic()?,
+            host: Arc::new(Mutex::new(crate::env::host::BasicHost)),
+            env: Arc::new(Mutex::new(Environment::basic()?)),
         })
     }
 
@@ -36,11 +36,11 @@ impl Context {
         &mut self,
         command: Arc<dyn Command>,
         arg_list: Vec<Value>,
-        input: VecDeque<Value>,
-    ) -> Result<VecDeque<ReturnValue>, ShellError> {
+        input: InputStream,
+    ) -> Result<OutputStream, ShellError> {
         let command_args = CommandArgs {
-            host: &mut self.host,
-            env: &self.env,
+            host: self.host.clone(),
+            env: self.env.clone(),
             args: arg_list,
             input,
         };
diff --git a/src/format/entries.rs b/src/format/entries.rs
index 02845c0854..c619f98b15 100644
--- a/src/format/entries.rs
+++ b/src/format/entries.rs
@@ -50,8 +50,10 @@ pub struct EntriesListView {
 }
 
 impl EntriesListView {
-    crate fn from_stream(values: VecDeque<Value>) -> EntriesListView {
-        EntriesListView { values }
+    crate async fn from_stream(values: InputStream) -> EntriesListView {
+        EntriesListView {
+            values: values.collect().await,
+        }
     }
 }
 
diff --git a/src/main.rs b/src/main.rs
index 6cf266b286..3f08472912 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,6 @@
 #![feature(crate_visibility_modifier)]
 #![feature(in_band_lifetimes)]
+#![feature(async_await)]
 
 mod cli;
 mod commands;
@@ -16,5 +17,6 @@ mod stream;
 use std::error::Error;
 
 fn main() -> Result<(), Box<Error>> {
-    crate::cli::cli()
+    futures::executor::block_on(crate::cli::cli());
+    Ok(())
 }
diff --git a/src/parser/parse.rs b/src/parser/parse.rs
index 6ad5807a0d..c379eab6d4 100644
--- a/src/parser/parse.rs
+++ b/src/parser/parse.rs
@@ -17,7 +17,7 @@ pub enum Item {
     Operator(Operator),
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub enum Operator {
     Equal,
     NotEqual,
diff --git a/src/prelude.rs b/src/prelude.rs
index 0480c26932..ebf084ad9f 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -4,4 +4,10 @@ crate use crate::context::Context;
 crate use crate::env::{Environment, Host};
 crate use crate::errors::ShellError;
 crate use crate::object::{Primitive, Value};
+#[allow(unused)]
+crate use crate::stream::{empty_stream, single_output, InputStream, OutputStream};
+#[allow(unused)]
+crate use futures::{Future, FutureExt, Stream, StreamExt};
 crate use std::collections::VecDeque;
+crate use std::pin::Pin;
+crate use std::sync::{Arc, Mutex};
diff --git a/src/stream.rs b/src/stream.rs
index e69de29bb2..dc4def8cba 100644
--- a/src/stream.rs
+++ b/src/stream.rs
@@ -0,0 +1,16 @@
+use crate::prelude::*;
+use futures::stream::BoxStream;
+
+pub type InputStream = BoxStream<'static, Value>;
+pub type OutputStream = BoxStream<'static, ReturnValue>;
+
+crate fn empty_stream() -> OutputStream {
+    VecDeque::new().boxed()
+}
+
+crate fn single_output(item: Value) -> OutputStream {
+    let value = ReturnValue::Value(item);
+    let mut vec = VecDeque::new();
+    vec.push_back(value);
+    vec.boxed()
+}