Early work on scripting features

src/builtin/mod.rs

@@ -1,3 +1,7 @@
+use nix::unistd::Pid;
+
+use crate::{jobs::{ChildProc, JobBldr}, libsh::error::ShResult, parse::{execute::prepare_argv, lex::{Span, Tk}, Redir}, procio::{IoFrame, IoStack}};
+
 pub mod echo;
 pub mod cd;
 pub mod export;
@@ -17,3 +21,55 @@ pub const BUILTINS: [&str;9] = [
 	"fg",
 	"bg"
 ];
+
+/// Sets up a builtin command
+///
+/// Prepares a builtin for execution by processing arguments, setting up redirections, and registering the command as a child process in the given `JobBldr`
+///
+/// # Parameters
+/// * argv - The vector of raw argument tokens
+/// * job - A mutable reference to a `JobBldr`
+/// * io_info - An optional 2-tuple consisting of a mutable reference to an `IoStack` and a vector of `Redirs`
+///
+/// # Behavior
+/// * Cleans, expands, and word splits the arg vector
+/// * Adds a new `ChildProc` to the job builder
+/// * Performs redirections, if any.
+///
+/// # Returns
+/// * The processed arg vector
+/// * The popped `IoFrame`, if any
+///
+/// # Notes
+/// * If redirections are given to this function, the caller must call `IoFrame.restore()` on the returned `IoFrame`
+/// * If redirections are given, the second field of the resulting tuple will *always* be `Some()`
+/// * If no redirections are given, the second field will *always* be `None`
+pub fn setup_builtin<'t>(
+	argv: Vec<Tk<'t>>,
+	job: &'t mut JobBldr,
+	io_info: Option<(&mut IoStack,Vec<Redir>)>,
+) -> ShResult<(Vec<(String,Span<'t>)>, Option<IoFrame>)> {
+	let mut argv: Vec<(String,Span)> = prepare_argv(argv);
+
+	let child_pgid = if let Some(pgid) = job.pgid() {
+		pgid
+	} else {
+		job.set_pgid(Pid::this());
+		Pid::this()
+	};
+	let cmd_name = argv.remove(0).0;
+	let child = ChildProc::new(Pid::this(), Some(&cmd_name), Some(child_pgid))?;
+	job.push_child(child);
+
+	let io_frame = if let Some((io_stack,redirs)) = io_info {
+		io_stack.append_to_frame(redirs);
+		let mut io_frame = io_stack.pop_frame();
+		io_frame.redirect()?;
+		Some(io_frame)
+	} else {
+		None
+	};
+
+	// We return the io_frame because the caller needs to also call io_frame.restore()
+	Ok((argv,io_frame))
+}