implemented '<>' redirects, and the 'seek' builtin

'seek' is a wrapper around the lseek() syscall

added noclobber to core shopts and implemented '>|' redirection syntax

properly implemented fd close syntax

fixed saved fds being leaked into exec'd programs

src/builtin/seek.rs

@@ -0,0 +1,253 @@
+use nix::{libc::STDOUT_FILENO, unistd::{Whence, lseek, write}};
+
+use crate::{getopt::{Opt, OptSpec, get_opts_from_tokens}, libsh::error::{ShErr, ShErrKind, ShResult}, parse::{NdRule, Node, execute::prepare_argv}, procio::borrow_fd, state};
+
+pub const LSEEK_OPTS: [OptSpec;2] = [
+	OptSpec {
+		opt: Opt::Short('c'),
+		takes_arg: false
+	},
+	OptSpec {
+		opt: Opt::Short('e'),
+		takes_arg: false
+	},
+];
+
+pub struct LseekOpts {
+	cursor_rel: bool,
+	end_rel: bool
+}
+
+pub fn seek(node: Node) -> ShResult<()> {
+	let NdRule::Command {
+		assignments: _,
+		argv,
+	} = node.class else { unreachable!() };
+
+	let (argv, opts) = get_opts_from_tokens(argv, &LSEEK_OPTS)?;
+	let lseek_opts = get_lseek_opts(opts)?;
+	let mut argv = prepare_argv(argv)?.into_iter();
+	argv.next(); // drop 'seek'
+
+	let Some(fd) = argv.next() else {
+		return Err(ShErr::simple(
+			ShErrKind::ExecFail,
+			"lseek: Missing required argument 'fd'",
+		));
+	};
+	let Ok(fd) = fd.0.parse::<u32>() else {
+		return Err(ShErr::at(
+			ShErrKind::ExecFail,
+			fd.1,
+			"Invalid file descriptor",
+		).with_note("file descriptors are integers"));
+	};
+
+	let Some(offset) = argv.next() else {
+		return Err(ShErr::simple(
+			ShErrKind::ExecFail,
+			"lseek: Missing required argument 'offset'",
+		));
+	};
+	let Ok(offset) = offset.0.parse::<i64>() else {
+		return Err(ShErr::at(
+			ShErrKind::ExecFail,
+			offset.1,
+			"Invalid offset",
+		).with_note("offset can be a positive or negative integer"));
+	};
+
+	let whence = if lseek_opts.cursor_rel {
+		Whence::SeekCur
+	} else if lseek_opts.end_rel {
+		Whence::SeekEnd
+	} else {
+		Whence::SeekSet
+	};
+
+	match lseek(fd as i32, offset, whence) {
+		Ok(new_offset) => {
+			let stdout = borrow_fd(STDOUT_FILENO);
+			let buf = new_offset.to_string() + "\n";
+			write(stdout, buf.as_bytes())?;
+		}
+		Err(e) => {
+			state::set_status(1);
+			return Err(e.into())
+		}
+	}
+
+	state::set_status(0);
+	Ok(())
+}
+
+pub fn get_lseek_opts(opts: Vec<Opt>) -> ShResult<LseekOpts> {
+	let mut lseek_opts = LseekOpts {
+		cursor_rel: false,
+		end_rel: false,
+	};
+
+  for opt in opts {
+    match opt {
+      Opt::Short('c') => lseek_opts.cursor_rel = true,
+      Opt::Short('e') => lseek_opts.end_rel = true,
+      _ => {
+        return Err(ShErr::simple(
+          ShErrKind::ExecFail,
+          format!("lseek: Unexpected flag '{opt}'"),
+        ));
+      }
+    }
+  }
+
+  Ok(lseek_opts)
+}
+
+#[cfg(test)]
+mod tests {
+  use crate::testutil::{TestGuard, test_input};
+  use pretty_assertions::assert_eq;
+
+  #[test]
+  fn seek_set_beginning() {
+    let dir = tempfile::TempDir::new().unwrap();
+    let path = dir.path().join("seek.txt");
+    std::fs::write(&path, "hello world\n").unwrap();
+    let g = TestGuard::new();
+
+    test_input(format!("exec 9<> {}", path.display())).unwrap();
+    test_input("seek 9 0").unwrap();
+
+    let out = g.read_output();
+    assert_eq!(out, "0\n");
+  }
+
+  #[test]
+  fn seek_set_offset() {
+    let dir = tempfile::TempDir::new().unwrap();
+    let path = dir.path().join("seek.txt");
+    std::fs::write(&path, "hello world\n").unwrap();
+    let g = TestGuard::new();
+
+    test_input(format!("exec 9<> {}", path.display())).unwrap();
+    test_input("seek 9 6").unwrap();
+
+    let out = g.read_output();
+    assert_eq!(out, "6\n");
+  }
+
+  #[test]
+  fn seek_then_read() {
+    let dir = tempfile::TempDir::new().unwrap();
+    let path = dir.path().join("seek.txt");
+    std::fs::write(&path, "hello world\n").unwrap();
+    let g = TestGuard::new();
+
+    test_input(format!("exec 9<> {}", path.display())).unwrap();
+    test_input("seek 9 6").unwrap();
+    // Clear the seek output
+    g.read_output();
+
+    test_input("read line <&9").unwrap();
+    let val = crate::state::read_vars(|v| v.get_var("line"));
+    assert_eq!(val, "world");
+  }
+
+  #[test]
+  fn seek_cur_relative() {
+    let dir = tempfile::TempDir::new().unwrap();
+    let path = dir.path().join("seek.txt");
+    std::fs::write(&path, "abcdefghij\n").unwrap();
+    let g = TestGuard::new();
+
+    test_input(format!("exec 9<> {}", path.display())).unwrap();
+    test_input("seek 9 3").unwrap();
+    test_input("seek -c 9 4").unwrap();
+
+    let out = g.read_output();
+    assert_eq!(out, "3\n7\n");
+  }
+
+  #[test]
+  fn seek_end() {
+    let dir = tempfile::TempDir::new().unwrap();
+    let path = dir.path().join("seek.txt");
+    std::fs::write(&path, "hello\n").unwrap(); // 6 bytes
+    let g = TestGuard::new();
+
+    test_input(format!("exec 9<> {}", path.display())).unwrap();
+    test_input("seek -e 9 0").unwrap();
+
+    let out = g.read_output();
+    assert_eq!(out, "6\n");
+  }
+
+  #[test]
+  fn seek_end_negative() {
+    let dir = tempfile::TempDir::new().unwrap();
+    let path = dir.path().join("seek.txt");
+    std::fs::write(&path, "hello\n").unwrap(); // 6 bytes
+    let g = TestGuard::new();
+
+    test_input(format!("exec 9<> {}", path.display())).unwrap();
+    test_input("seek -e 9 -2").unwrap();
+
+    let out = g.read_output();
+    assert_eq!(out, "4\n");
+  }
+
+  #[test]
+  fn seek_write_overwrite() {
+    let dir = tempfile::TempDir::new().unwrap();
+    let path = dir.path().join("seek.txt");
+    std::fs::write(&path, "hello world\n").unwrap();
+    let _g = TestGuard::new();
+
+    test_input(format!("exec 9<> {}", path.display())).unwrap();
+    test_input("seek 9 6").unwrap();
+    test_input("echo -n 'WORLD' >&9").unwrap();
+
+    let contents = std::fs::read_to_string(&path).unwrap();
+    assert_eq!(contents, "hello WORLD\n");
+  }
+
+  #[test]
+  fn seek_rewind_full_read() {
+    let dir = tempfile::TempDir::new().unwrap();
+    let path = dir.path().join("seek.txt");
+    std::fs::write(&path, "abc\n").unwrap();
+    let g = TestGuard::new();
+
+    test_input(format!("exec 9<> {}", path.display())).unwrap();
+    // Read moves cursor to EOF
+    test_input("read line <&9").unwrap();
+    // Rewind
+    test_input("seek 9 0").unwrap();
+    // Clear output from seek
+    g.read_output();
+    // Read again from beginning
+    test_input("read line <&9").unwrap();
+
+    let val = crate::state::read_vars(|v| v.get_var("line"));
+    assert_eq!(val, "abc");
+  }
+
+  #[test]
+  fn seek_bad_fd() {
+    let _g = TestGuard::new();
+
+    let result = test_input("seek 99 0");
+    assert!(result.is_err());
+  }
+
+  #[test]
+  fn seek_missing_args() {
+    let _g = TestGuard::new();
+
+    let result = test_input("seek");
+    assert!(result.is_err());
+
+    let result = test_input("seek 9");
+    assert!(result.is_err());
+  }
+}