A bit more infra

src/commands/cd.rs

@@ -0,0 +1,21 @@
+use crate::errors::ShellError;
+use crate::object::process::Process;
+use crate::object::{DirEntry, ShellObject, Value};
+use derive_new::new;
+use std::path::{Path, PathBuf};
+use sysinfo::SystemExt;
+
+#[derive(new)]
+pub struct Cd;
+
+impl crate::Command for Cd {
+    fn run(
+        &mut self,
+        args: Vec<String>,
+        _host: &dyn crate::Host,
+        env: &mut crate::Environment,
+    ) -> Result<Value, ShellError> {
+        env.cwd = dunce::canonicalize(env.cwd().join(&args[0]).as_path())?;
+        Ok(Value::nothing())
+    }
+}

src/commands/command.rs

@@ -4,6 +4,7 @@ use crate::object::Value;
 pub trait Command {
     fn run(
         &mut self,
+        args: Vec<String>,
         host: &dyn crate::Host,
         env: &mut crate::Environment,
     ) -> Result<Value, ShellError>;

src/commands/ls.rs

@@ -10,6 +10,7 @@ pub struct Ls;
 impl crate::Command for Ls {
     fn run(
         &mut self,
+        _args: Vec<String>,
         _host: &dyn crate::Host,
         env: &mut crate::Environment,
     ) -> Result<Value, ShellError> {

src/commands/ps.rs

@@ -12,6 +12,7 @@ pub struct Ps {
 impl crate::Command for Ps {
     fn run(
         &mut self,
+        _args: Vec<String>,
         _host: &dyn crate::Host,
         _env: &mut crate::Environment,
     ) -> Result<Value, ShellError> {