Implemented command substitution

src/builtin/flowctl.rs

@@ -7,7 +7,7 @@ pub fn flowctl(node: Node, kind: ShErrKind) -> ShResult<()> {
 	};
 	let mut code = 0;
 
-	let mut argv = prepare_argv(argv);
+	let mut argv = prepare_argv(argv)?;
 	let cmd = argv.remove(0).0;
 
 	if !argv.is_empty() {

src/builtin/mod.rs

@@ -56,7 +56,7 @@ pub fn setup_builtin(
 	job: &mut JobBldr,
 	io_mode: Option<(&mut IoStack,Vec<Redir>)>,
 ) -> ShResult<(Vec<(String,Span)>, Option<IoFrame>)> {
-	let mut argv: Vec<(String,Span)> = prepare_argv(argv);
+	let mut argv: Vec<(String,Span)> = prepare_argv(argv)?;
 
 	let child_pgid = if let Some(pgid) = job.pgid() {
 		pgid

src/expand.rs

@@ -1,6 +1,6 @@
 use std::collections::{HashSet, VecDeque};
 
-use crate::{libsh::error::ShResult, parse::lex::{is_field_sep, is_hard_sep, is_keyword, LexFlags, LexStream, Span, Tk, TkFlags, TkRule}, prelude::*, state::{read_logic, read_meta, read_vars, write_meta}};
+use crate::{exec_input, libsh::error::{ShErr, ShErrKind, ShResult}, parse::{lex::{is_field_sep, is_hard_sep, is_keyword, LexFlags, LexStream, Span, Tk, TkFlags, TkRule}, Redir, RedirType}, prelude::*, procio::{IoBuf, IoFrame, IoMode}, state::{read_logic, read_meta, read_vars, write_meta}};
 
 /// Variable substitution marker
 pub const VAR_SUB: char = '\u{fdd0}';
@@ -16,10 +16,10 @@ impl Tk {
 	/// tokens: A vector of raw tokens lexed from the expansion result
 	/// span: The span of the original token that is being expanded
 	/// flags: some TkFlags
-	pub fn expand(self, span: Span, flags: TkFlags) -> Self {
-		let exp = Expander::new(self).expand();
+	pub fn expand(self, span: Span, flags: TkFlags) -> ShResult<Self> {
+		let exp = Expander::new(self).expand()?;
 		let class = TkRule::Expanded { exp };
-		Self { class, span, flags, }
+		Ok(Self { class, span, flags, })
 	}
 	pub fn get_words(&self) -> Vec<String> {
 		match &self.class {
@@ -38,9 +38,9 @@ impl Expander {
 		let unescaped = unescape_str(raw.span.as_str());
 		Self { raw: unescaped }
 	}
-	pub fn expand(&mut self) -> Vec<String> {
-		self.raw = self.expand_raw();
-		self.split_words()
+	pub fn expand(&mut self) -> ShResult<Vec<String>> {
+		self.raw = self.expand_raw()?;
+		Ok(self.split_words())
 	}
 	pub fn split_words(&mut self) -> Vec<String> {
 		let mut words = vec![];
@@ -68,18 +68,38 @@ impl Expander {
 		}
 		words
 	}
-	pub fn expand_raw(&self) -> String {
-		let mut chars = self.raw.chars();
+	pub fn expand_raw(&self) -> ShResult<String> {
+		let mut chars = self.raw.chars().peekable();
 		let mut result = String::new();
 		let mut var_name = String::new();
 		let mut in_brace = false;
 
-		// TODO: implement error handling for unclosed braces
 		while let Some(ch) = chars.next() {
 			match ch {
 				VAR_SUB => {
 					while let Some(ch) = chars.next() {
 						match ch {
+							'(' if var_name.is_empty() => {
+								let mut paren_stack = vec!['('];
+								let mut subsh_body = String::new();
+								while let Some(ch) = chars.next() {
+									flog!(DEBUG, "looping");
+									flog!(DEBUG, subsh_body);
+									match ch {
+										'(' => {
+											paren_stack.push(ch);
+											subsh_body.push(ch);
+										}
+										')' => {
+											paren_stack.pop();
+											if paren_stack.is_empty() { break };
+											subsh_body.push(ch);
+										}
+										_ => subsh_body.push(ch)
+									}
+								}
+								result.push_str(&expand_cmd_sub(&subsh_body)?);
+							}
 							'{' => in_brace = true,
 							'}' if in_brace => {
 								let var_val = read_vars(|v| v.get_var(&var_name));
@@ -106,7 +126,44 @@ impl Expander {
 				_ => result.push(ch)
 			}
 		}
-		result
+		Ok(result)
+	}
+}
+
+/// Get the command output of a given command input as a String
+pub fn expand_cmd_sub(raw: &str) -> ShResult<String> {
+	flog!(DEBUG, "in expand_cmd_sub");
+	let (rpipe,wpipe) = IoMode::get_pipes();
+	let cmd_sub_redir = Redir::new(wpipe, RedirType::Output);
+	let mut cmd_sub_io_frame = IoFrame::from_redir(cmd_sub_redir);
+	let mut io_buf = IoBuf::new(rpipe);
+
+	match unsafe { fork()? } {
+		ForkResult::Child => {
+			if let Err(e) = cmd_sub_io_frame.redirect() {
+				eprintln!("{e}");
+				exit(1);
+			}
+
+			if let Err(e) = exec_input(raw.to_string()) {
+				eprintln!("{e}");
+				exit(1);
+			}
+			exit(0);
+		}
+		ForkResult::Parent { child } => {
+			std::mem::drop(cmd_sub_io_frame); // Closes the write pipe
+			let status = waitpid(child, Some(WtFlag::WSTOPPED))?;
+			match status {
+				WtStat::Exited(_, _) => {
+					flog!(DEBUG, "filling buffer");
+					io_buf.fill_buffer()?;
+					flog!(DEBUG, "done");
+					Ok(io_buf.as_str()?.trim().to_string())
+				}
+				_ => return Err(ShErr::simple(ShErrKind::InternalErr, "Command sub failed"))
+			}
+		}
 	}
 }
 

src/libsh/utils.rs

@@ -8,6 +8,12 @@ pub trait VecDequeExt<T> {
 	fn to_vec(self) -> Vec<T>;
 }
 
+pub trait CharDequeUtils {
+	fn to_string(self) -> String;
+	fn ends_with(&self, pat: &str) -> bool;
+	fn starts_with(&self, pat: &str) -> bool;
+}
+
 pub trait TkVecUtils<Tk> {
 	fn get_span(&self) -> Option<Span>;
 	fn debug_tokens(&self);
@@ -26,6 +32,42 @@ impl<T> VecDequeExt<T> for VecDeque<T> {
 	}
 }
 
+impl CharDequeUtils for VecDeque<char> {
+	fn to_string(mut self) -> String {
+		let mut result = String::with_capacity(self.len());
+		while let Some(ch) = self.pop_front() {
+			result.push(ch);
+		}
+		result
+	}
+
+	fn ends_with(&self, pat: &str) -> bool {
+		let pat_chars = pat.chars();
+		let self_len = self.len();
+
+		// If pattern is longer than self, return false
+		if pat_chars.clone().count() > self_len {
+			return false;
+		}
+
+		// Compare from the back
+		self.iter().rev().zip(pat_chars.rev()).all(|(c1, c2)| c1 == &c2)
+	}
+
+	fn starts_with(&self, pat: &str) -> bool {
+		let pat_chars = pat.chars();
+		let self_len = self.len();
+
+		// If pattern is longer than self, return false
+		if pat_chars.clone().count() > self_len {
+			return false;
+		}
+
+		// Compare from the front
+		self.iter().zip(pat_chars).all(|(c1, c2)| c1 == &c2)
+	}
+}
+
 impl TkVecUtils<Tk> for Vec<Tk> {
 	fn get_span(&self) -> Option<Span> {
 		if let Some(first_tk) = self.first() {

src/parse/execute.rs

@@ -18,13 +18,13 @@ pub struct ExecArgs {
 }
 
 impl ExecArgs {
-	pub fn new(argv: Vec<Tk>) -> Self {
+	pub fn new(argv: Vec<Tk>) -> ShResult<Self> {
 		assert!(!argv.is_empty());
-		let argv = prepare_argv(argv);
+		let argv = prepare_argv(argv)?;
 		let cmd = Self::get_cmd(&argv);
 		let argv = Self::get_argv(argv);
 		let envp = Self::get_envp();
-		Self { cmd, argv, envp }
+		Ok(Self { cmd, argv, envp })
 	}
 	pub fn get_cmd(argv: &[(String,Span)]) -> (CString,Span) {
 		(CString::new(argv[0].0.as_str()).unwrap(),argv[0].1.clone())
@@ -197,7 +197,7 @@ impl Dispatcher {
 		self.io_stack.append_to_frame(case_stmt.redirs);
 
 		flog!(DEBUG,pattern.span.as_str());
-		let exp_pattern = pattern.clone().expand(pattern.span.clone(), pattern.flags.clone());
+		let exp_pattern = pattern.clone().expand(pattern.span.clone(), pattern.flags.clone())?;
 		let pattern_raw = exp_pattern
 			.get_words()
 			.first()
@@ -396,7 +396,7 @@ impl Dispatcher {
 
 		self.io_stack.append_to_frame(cmd.redirs);
 
-		let exec_args = ExecArgs::new(argv);
+		let exec_args = ExecArgs::new(argv)?;
 		let io_frame = self.io_stack.pop_frame();
 		run_fork(
 			io_frame,
@@ -453,18 +453,18 @@ impl Dispatcher {
 	}
 }
 
-pub fn prepare_argv(argv: Vec<Tk>) -> Vec<(String,Span)> {
+pub fn prepare_argv(argv: Vec<Tk>) -> ShResult<Vec<(String,Span)>> {
 	let mut args = vec![];
 
 	for arg in argv {
 		let flags = arg.flags;
 		let span = arg.span.clone();
-		let expanded = arg.expand(span.clone(), flags);
+		let expanded = arg.expand(span.clone(), flags)?;
 		for exp in expanded.get_words() {
 			args.push((exp,span.clone()))
 		}
 	}
-	args
+	Ok(args)
 }
 
 pub fn run_fork<'t,C,P>(

src/parse/lex.rs

@@ -1,8 +1,8 @@
-use std::{fmt::Display, ops::{Bound, Deref, Range, RangeBounds}, str::Chars};
+use std::{collections::VecDeque, fmt::Display, iter::Peekable, ops::{Bound, Deref, Range, RangeBounds}, str::Chars};
 
 use bitflags::bitflags;
 
-use crate::{builtin::BUILTINS, libsh::error::{ShErr, ShErrKind, ShResult}, prelude::*};
+use crate::{builtin::BUILTINS, libsh::{error::{ShErr, ShErrKind, ShResult}, utils::CharDequeUtils}, prelude::*};
 
 pub const KEYWORDS: [&'static str;14] = [
 	"if",
@@ -137,9 +137,10 @@ bitflags! {
 		/// This is a  keyword that opens a new block statement, like 'if' and 'while'
 		const OPENER   = 0b0000000000000010;
 		const IS_CMD   = 0b0000000000000100;
-		const IS_OP   = 0b0000000000001000;
-		const ASSIGN  = 0b0000000000010000;
-		const BUILTIN = 0b0000000000100000;
+		const IS_SUBSH = 0b0000000000001000;
+		const IS_OP    = 0b0000000000010000;
+		const ASSIGN   = 0b0000000000100000;
+		const BUILTIN  = 0b0000000001000000;
 	}
 }
 
@@ -309,7 +310,7 @@ impl LexStream {
 		assert!(self.cursor <= self.source.len());
 		let slice = self.slice_from_cursor().unwrap().to_string();
 		let mut pos = self.cursor;
-		let mut chars = slice.chars();
+		let mut chars = slice.chars().peekable();
 		let mut quote_pos = None;
 
 		if let Some(count) = case_pat_lookahead(chars.clone()) {
@@ -331,10 +332,89 @@ impl LexStream {
 				}
 				'\\' => {
 					pos += 1;
-					if chars.next().is_some() {
-						pos += 1;
+					if let Some(ch) = chars.next() {
+						pos += ch.len_utf8();
 					}
 				}
+				'$' if chars.peek() == Some(&'(') => {
+					pos += 2;
+					chars.next();
+					let mut paren_stack = vec!['('];
+					let paren_pos = pos;
+					while let Some(ch) = chars.next() {
+						match ch {
+							'\\' => {
+								pos += 1;
+								if let Some(next_ch) = chars.next() {
+									pos += next_ch.len_utf8();
+								}
+							}
+							'(' => {
+								pos += 1;
+								paren_stack.push(ch);
+							}
+							')' => {
+								pos += 1;
+								paren_stack.pop();
+								if paren_stack.is_empty() {
+									break
+								}
+							}
+							_ => pos += ch.len_utf8()
+						}
+					}
+					if !paren_stack.is_empty() {
+						return Err(
+							ShErr::full(
+								ShErrKind::ParseErr,
+								"Unclosed subshell",
+								Span::new(paren_pos..paren_pos + 1, self.source.clone())
+							)
+						)
+					}
+				}
+				'(' if self.next_is_cmd() => {
+					let mut paren_stack = vec!['('];
+					let paren_pos = pos;
+					while let Some(ch) = chars.next() {
+						pos += ch.len_utf8();
+						match ch {
+							'\\' => {
+								if let Some(next_ch) = chars.next() {
+									pos += next_ch.len_utf8();
+								}
+							}
+							'(' => {
+								pos += 1;
+								paren_stack.push(ch);
+							}
+							')' => {
+								pos += 1;
+								paren_stack.pop();
+								if paren_stack.is_empty() {
+									break
+								}
+							}
+							_ => continue
+						}
+					}
+					if !paren_stack.is_empty() {
+						return Err(
+							ShErr::full(
+								ShErrKind::ParseErr,
+								"Unclosed subshell",
+								Span::new(paren_pos..paren_pos + 1, self.source.clone())
+							)
+						)
+					}
+					let mut subsh_tk = self.get_token(self.cursor..pos, TkRule::Str);
+					subsh_tk.flags |= TkFlags::IS_CMD;
+					subsh_tk.flags |= TkFlags::IS_SUBSH;
+					self.cursor = pos;
+					self.set_next_is_cmd(true);
+					flog!(DEBUG, subsh_tk);
+					return Ok(subsh_tk)
+				}
 				'{' if pos == self.cursor && self.next_is_cmd() => {
 					pos += 1;
 					let mut tk = self.get_token(self.cursor..pos, TkRule::BraceGrpStart);
@@ -384,6 +464,7 @@ impl LexStream {
 			}
 		}
 		let mut new_tk = self.get_token(self.cursor..pos, TkRule::Str);
+		flog!(DEBUG,new_tk);
 		if self.in_quote && !self.flags.contains(LexFlags::LEX_UNFINISHED) {
 			return Err(
 				ShErr::full(
@@ -428,6 +509,7 @@ impl LexStream {
 			}
 		}
 		self.cursor = pos;
+		flog!(DEBUG, self.slice_from_cursor());
 		Ok(new_tk)
 	}
 	pub fn get_token(&self, range: Range<usize>, class: TkRule) -> Tk {
@@ -595,7 +677,23 @@ pub fn is_keyword(slice: &str) -> bool {
 	(slice.ends_with("()") && !slice.ends_with("\\()"))
 }
 
-pub fn case_pat_lookahead(mut chars: Chars) -> Option<usize> {
+pub fn lookahead(pat: &str, mut chars: Chars) -> Option<usize> {
+	let mut pos = 0;
+	let mut char_deque = VecDeque::new();
+	while let Some(ch) = chars.next() {
+		char_deque.push_back(ch);
+		if char_deque.len() > pat.len() {
+			char_deque.pop_front();
+		}
+		if char_deque.starts_with(pat) {
+			return Some(pos)
+		}
+		pos += 1;
+	}
+	None
+}
+
+pub fn case_pat_lookahead(mut chars: Peekable<Chars>) -> Option<usize> {
 	let mut pos = 0;
 	while let Some(ch) = chars.next() {
 		pos += 1;

src/parse/mod.rs

@@ -42,6 +42,7 @@ impl ParsedSrc {
 		for token in LexStream::new(self.src.clone(), LexFlags::empty()) {
 			tokens.push(token?);
 		}
+		flog!(DEBUG,tokens);
 
 		let mut nodes = vec![];
 		for result in ParseStream::new(tokens) {

src/procio.rs

@@ -1,6 +1,6 @@
 use std::{fmt::Debug, ops::{Deref, DerefMut}};
 
-use crate::{libsh::{error::ShResult, utils::RedirVecUtils}, parse::{Redir, RedirType}, prelude::*};
+use crate::{libsh::{error::{ShErr, ShErrKind, ShResult}, utils::RedirVecUtils}, parse::{Redir, RedirType}, prelude::*};
 
 // Credit to fish-shell for many of the implementation ideas present in this module
 // https://fishshell.com/
@@ -10,6 +10,7 @@ pub enum IoMode {
 	Fd { tgt_fd: RawFd, src_fd: Rc<OwnedFd> },
 	File { tgt_fd: RawFd, file: Rc<File> },
 	Pipe { tgt_fd: RawFd, pipe: Rc<OwnedFd> },
+	Buffer { buf: String, pipe: Rc<OwnedFd> }
 }
 
 impl IoMode {
@@ -29,14 +30,16 @@ impl IoMode {
 		match self {
 			IoMode::Fd { tgt_fd, src_fd: _ } |
 			IoMode::File { tgt_fd, file: _ } |
-			IoMode::Pipe { tgt_fd, pipe: _ } => *tgt_fd
+			IoMode::Pipe { tgt_fd, pipe: _ } => *tgt_fd,
+			_ => panic!()
 		}
 	}
 	pub fn src_fd(&self) -> RawFd {
 		match self {
 			IoMode::Fd { tgt_fd: _, src_fd } => src_fd.as_raw_fd(),
 			IoMode::File { tgt_fd: _, file } => file.as_raw_fd(),
-			IoMode::Pipe { tgt_fd: _, pipe } => pipe.as_raw_fd()
+			IoMode::Pipe { tgt_fd: _, pipe } => pipe.as_raw_fd(),
+			_ => panic!()
 		}
 	}
 	pub fn get_pipes() -> (Self,Self) {
@@ -55,6 +58,50 @@ impl Read for IoMode {
 	}
 }
 
+pub struct IoBuf<R: Read> {
+	buf: Vec<u8>,
+	reader: R,
+}
+
+impl<R: Read> IoBuf<R> {
+	pub fn new(reader: R) -> Self {
+		Self {
+			buf: Vec::new(),
+			reader,
+		}
+	}
+
+	/// Reads exactly `size` bytes (or fewer if EOF) into the buffer
+	pub fn read_buffer(&mut self, size: usize) -> io::Result<()> {
+		let mut temp_buf = vec![0; size]; // Temporary buffer
+		let bytes_read = self.reader.read(&mut temp_buf)?;
+		self.buf.extend_from_slice(&temp_buf[..bytes_read]); // Append only what was read
+		Ok(())
+	}
+
+	/// Continuously reads until EOF
+	pub fn fill_buffer(&mut self) -> io::Result<()> {
+		let mut temp_buf = vec![0; 1024]; // Read in chunks
+		loop {
+			flog!(DEBUG, "reading bytes");
+			let bytes_read = self.reader.read(&mut temp_buf)?;
+			flog!(DEBUG, bytes_read);
+			if bytes_read == 0 {
+				break; // EOF reached
+			}
+			self.buf.extend_from_slice(&temp_buf[..bytes_read]);
+		}
+		Ok(())
+	}
+
+	/// Get current buffer contents as a string (if valid UTF-8)
+	pub fn as_str(&self) -> ShResult<&str> {
+		std::str::from_utf8(&self.buf).map_err(|_| {
+			ShErr::simple(ShErrKind::InternalErr, "Invalid utf-8 in IoBuf")
+		})
+	}
+}
+
 /// A struct wrapping three fildescs representing `stdin`, `stdout`, and `stderr` respectively
 #[derive(Debug,Clone)]
 pub struct IoGroup(RawFd,RawFd,RawFd);
@@ -74,6 +121,9 @@ impl<'e> IoFrame {
 	pub fn from_redirs(redirs: Vec<Redir>) -> Self {
 		Self { redirs, saved_io: None }
 	}
+	pub fn from_redir(redir: Redir) -> Self {
+		Self { redirs: vec![redir], saved_io: None }
+	}
 
 	/// Splits the frame into two frames
 	///