diff --git a/src/commands.rs b/src/commands.rs
new file mode 100644
index 0000000..11baafa
--- /dev/null
+++ b/src/commands.rs
@@ -0,0 +1,71 @@
+use crate::runtime::Shell;
+use anyhow::Result;
+use std::collections::HashMap;
+
+mod cd;
+mod echo;
+mod environment;
+mod exit;
+mod pwd;
+mod source;
+mod status;
+
+#[derive(Debug)]
+pub(crate) struct BuiltinResult {
+    pub status: i32,
+    pub stdout: Vec<u8>,
+    pub stderr: Vec<u8>,
+}
+
+impl BuiltinResult {
+    fn success() -> Self {
+        Self::status(0)
+    }
+
+    fn status(status: i32) -> Self {
+        Self {
+            status,
+            stdout: Vec::new(),
+            stderr: Vec::new(),
+        }
+    }
+
+    fn stdout(status: i32, stdout: Vec<u8>) -> Self {
+        Self {
+            status,
+            stdout,
+            stderr: Vec::new(),
+        }
+    }
+
+    fn stderr(status: i32, stderr: Vec<u8>) -> Self {
+        Self {
+            status,
+            stdout: Vec::new(),
+            stderr,
+        }
+    }
+}
+
+pub(crate) fn run(
+    shell: &mut Shell,
+    name: &str,
+    argv: &[String],
+    env_overlay: &HashMap<String, String>,
+) -> Result<Option<BuiltinResult>> {
+    let result = match name {
+        "cd" => cd::run(shell, argv)?,
+        "pwd" => pwd::run()?,
+        "exit" => exit::run(argv),
+        "export" => environment::export(shell, argv, env_overlay),
+        "unset" => environment::unset(shell, argv),
+        "set" => environment::set(shell)?,
+        "true" => status::true_(),
+        "false" => status::false_(),
+        "echo" => echo::run(argv)?,
+        "." | "source" => source::run(shell, argv)?,
+        _ => return Ok(None),
+    };
+
+    Ok(Some(result))
+}
diff --git a/src/commands/cd.rs b/src/commands/cd.rs
new file mode 100644
index 0000000..edab2d9
--- /dev/null
+++ b/src/commands/cd.rs
@@ -0,0 +1,22 @@
+use crate::commands::BuiltinResult;
+use crate::path::shell_path;
+use crate::runtime::Shell;
+use anyhow::{Context, Result};
+use std::env;
+
+pub(crate) fn run(shell: &Shell, argv: &[String]) -> Result<BuiltinResult> {
+    let target = argv
+        .first()
+        .cloned()
+        .or_else(|| shell.vars.get("HOME").cloned())
+        .or_else(|| shell.vars.get("USERPROFILE").cloned())
+        .context("cd: missing destination and HOME/USERPROFILE is unset")?;
+
+    match env::set_current_dir(shell_path(&target)) {
+        Ok(()) => Ok(BuiltinResult::success()),
+        Err(err) => Ok(BuiltinResult::stderr(
+            1,
+            format!("cd: {err}\n").into_bytes(),
+        )),
+    }
+}
diff --git a/src/commands/echo.rs b/src/commands/echo.rs
new file mode 100644
index 0000000..a60ac42
--- /dev/null
+++ b/src/commands/echo.rs
@@ -0,0 +1,9 @@
+use crate::commands::BuiltinResult;
+use anyhow::Result;
+use std::io::Write;
+
+pub(crate) fn run(argv: &[String]) -> Result<BuiltinResult> {
+    let mut stdout = Vec::new();
+    writeln!(stdout, "{}", argv.join(" "))?;
+    Ok(BuiltinResult::stdout(0, stdout))
+}
diff --git a/src/commands/environment.rs b/src/commands/environment.rs
new file mode 100644
index 0000000..ecfb365
--- /dev/null
+++ b/src/commands/environment.rs
@@ -0,0 +1,40 @@
+use crate::commands::BuiltinResult;
+use crate::runtime::Shell;
+use anyhow::Result;
+use std::collections::HashMap;
+
+pub(crate) fn export(
+    shell: &mut Shell,
+    argv: &[String],
+    env_overlay: &HashMap<String, String>,
+) -> BuiltinResult {
+    for arg in argv {
+        if let Some((name, value)) = arg.split_once('=') {
+            shell.vars.insert(name.to_string(), value.to_string());
+        } else if let Some(value) = env_overlay.get(arg).cloned() {
+            shell.vars.insert(arg.to_string(), value);
+        }
+    }
+
+    BuiltinResult::success()
+}
+
+pub(crate) fn unset(shell: &mut Shell, argv: &[String]) -> BuiltinResult {
+    for arg in argv {
+        shell.vars.remove(arg);
+    }
+
+    BuiltinResult::success()
+}
+
+pub(crate) fn set(shell: &Shell) -> Result<BuiltinResult> {
+    let mut pairs: Vec<_> = shell.vars.iter().collect();
+    pairs.sort_by(|a, b| a.0.cmp(b.0));
+
+    let mut stdout = Vec::new();
+    for (key, value) in pairs {
+        stdout.extend_from_slice(format!("{key}={value}\n").as_bytes());
+    }
+
+    Ok(BuiltinResult::stdout(0, stdout))
+}
diff --git a/src/commands/exit.rs b/src/commands/exit.rs
new file mode 100644
index 0000000..c1bf54d
--- /dev/null
+++ b/src/commands/exit.rs
@@ -0,0 +1,9 @@
+use crate::commands::BuiltinResult;
+
+pub(crate) fn run(argv: &[String]) -> BuiltinResult {
+    let code = argv
+        .first()
+        .and_then(|s| s.parse::<i32>().ok())
+        .unwrap_or(0);
+    BuiltinResult::status(code)
+}
diff --git a/src/commands/pwd.rs b/src/commands/pwd.rs
new file mode 100644
index 0000000..ee69c6b
--- /dev/null
+++ b/src/commands/pwd.rs
@@ -0,0 +1,11 @@
+use crate::commands::BuiltinResult;
+use crate::path::display_path;
+use anyhow::Result;
+use std::env;
+
+pub(crate) fn run() -> Result<BuiltinResult> {
+    Ok(BuiltinResult::stdout(
+        0,
+        format!("{}\n", display_path(&env::current_dir()?)).into_bytes(),
+    ))
+}
diff --git a/src/commands/source.rs b/src/commands/source.rs
new file mode 100644
index 0000000..ffad074
--- /dev/null
+++ b/src/commands/source.rs
@@ -0,0 +1,14 @@
+use crate::commands::BuiltinResult;
+use crate::path::shell_path;
+use crate::runtime::{RunOptions, Shell};
+use anyhow::{Context, Result};
+
+pub(crate) fn run(shell: &mut Shell, argv: &[String]) -> Result<BuiltinResult> {
+    let path = argv.first().context(".: missing script path")?;
+    let source = std::fs::read_to_string(shell_path(path))
+        .with_context(|| format!("failed to read script {}", path))?;
+
+    Ok(BuiltinResult::status(
+        shell.run_script(&source, RunOptions::default())?,
+    ))
+}
diff --git a/src/commands/status.rs b/src/commands/status.rs
new file mode 100644
index 0000000..bfc2882
--- /dev/null
+++ b/src/commands/status.rs
@@ -0,0 +1,9 @@
+use crate::commands::BuiltinResult;
+
+pub(crate) fn true_() -> BuiltinResult {
+    BuiltinResult::success()
+}
+
+pub(crate) fn false_() -> BuiltinResult {
+    BuiltinResult::status(1)
+}
diff --git a/src/lib.rs b/src/lib.rs
index 83176cc..96d4656 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,4 @@
+mod commands;
 mod parser;
 mod path;
 mod runtime;
diff --git a/src/runtime.rs b/src/runtime.rs
index e536135..15567a1 100644
--- a/src/runtime.rs
+++ b/src/runtime.rs
@@ -1,5 +1,6 @@
+use crate::commands;
 use crate::parser::{Command as AstCommand, ListItem, Pipeline, RedirectKind, Word, parse};
-use crate::path::{display_path, is_explicit_path, shell_path};
+use crate::path::{is_explicit_path, shell_path};
 use anyhow::{Context, Result, bail};
 use std::collections::HashMap;
 use std::env;
@@ -13,7 +14,7 @@ pub struct RunOptions {}
 
 #[derive(Debug)]
 pub struct Shell {
-    vars: HashMap<String, String>,
+    pub(crate) vars: HashMap<String, String>,
     last_status: i32,
 }
 
@@ -150,79 +151,15 @@ impl Shell {
         command: &AstCommand,
         capture_stdout: bool,
     ) -> Result<Option<CommandOutput>> {
-        let mut stdout = Vec::new();
-        let mut stderr = Vec::new();
-        let status = match name {
-            "cd" => {
-                let target = argv
-                    .first()
-                    .cloned()
-                    .or_else(|| self.vars.get("HOME").cloned())
-                    .or_else(|| self.vars.get("USERPROFILE").cloned())
-                    .context("cd: missing destination and HOME/USERPROFILE is unset")?;
-                match env::set_current_dir(shell_path(&target)) {
-                    Ok(()) => 0,
-                    Err(err) => {
-                        writeln!(stderr, "cd: {err}")?;
-                        1
-                    }
-                }
-            }
-            "pwd" => {
-                writeln!(stdout, "{}", display_path(&env::current_dir()?))?;
-                0
-            }
-            "exit" => {
-                let code = argv
-                    .first()
-                    .and_then(|s| s.parse::<i32>().ok())
-                    .unwrap_or(0);
-                return Ok(Some(CommandOutput {
-                    status: code,
-                    stdout,
-                }));
-            }
-            "export" => {
-                for arg in argv {
-                    if let Some((name, value)) = arg.split_once('=') {
-                        self.vars.insert(name.to_string(), value.to_string());
-                    } else if let Some(value) = env_overlay.get(arg).cloned() {
-                        self.vars.insert(arg.to_string(), value);
-                    }
-                }
-                0
-            }
-            "unset" => {
-                for arg in argv {
-                    self.vars.remove(arg);
-                }
-                0
-            }
-            "set" => {
-                let mut pairs: Vec<_> = self.vars.iter().collect();
-                pairs.sort_by(|a, b| a.0.cmp(b.0));
-                for (key, value) in pairs {
-                    writeln!(stdout, "{key}={value}")?;
-                }
-                0
-            }
-            "true" => 0,
-            "false" => 1,
-            "echo" => {
-                writeln!(stdout, "{}", argv.join(" "))?;
-                0
-            }
-            "." | "source" => {
-                let path = argv.first().context(".: missing script path")?;
-                let source = std::fs::read_to_string(shell_path(path))
-                    .with_context(|| format!("failed to read script {}", path))?;
-                self.run_script(&source, RunOptions::default())?
-            }
-            _ => return Ok(None),
+        let Some(result) = commands::run(self, name, argv, env_overlay)? else {
+            return Ok(None);
         };
 
-        write_builtin_streams(command, capture_stdout, &stdout, &stderr)?;
-        Ok(Some(CommandOutput { status, stdout }))
+        write_builtin_streams(command, capture_stdout, &result.stdout, &result.stderr)?;
+        Ok(Some(CommandOutput {
+            status: result.status,
+            stdout: result.stdout,
+        }))
     }
 
     fn run_external(