From 2ebf74dd059ed777c7bfb2df3654735912d498e0 Mon Sep 17 00:00:00 2001
From: Jay Hemnani <193022578+jayhemnani9910@users.noreply.github.com>
Date: Sat, 24 Oct 2026 02:29:51 +0530
Subject: [PATCH 1/2] parser: read length without parentheses as length($0)

---
 lexer/src/lib.rs          |  2 +-
 parser/src/pratt.rs       | 13 ++++++++++---
 tests/by-util/test_awk.rs |  9 +++++++++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/lexer/src/lib.rs b/lexer/src/lib.rs
index 5c82dae..1640f64 100644
--- a/lexer/src/lib.rs
+++ b/lexer/src/lib.rs
@@ -107,7 +107,7 @@ pub enum Token<'a> {
     #[token("function", accept_expression)]
     #[token("func", |lex| parse_non_posix_keyword(lex, Token::Function))]
     Function,
-    #[token("length", accept_expression)]
+    #[token("length", accept_operator)]
     Length,
     #[token("substr", accept_expression)]
     Substr,
diff --git a/parser/src/pratt.rs b/parser/src/pratt.rs
index f002f00..0aa3439 100644
--- a/parser/src/pratt.rs
+++ b/parser/src/pratt.rs
@@ -9,9 +9,9 @@ use lexer::{Span, Token};
 use crate::{
     ArrayPlace, IdentifierExt, Lexer, Parser, Result,
     ast::{
-        ArrayOperator, Atom, BinaryOperator, BinaryPlaceOperator, BindingPower, Expr, ExprNode,
-        Getline, Place, Redirection, Ternary, UnaryOperator, UnaryPlaceOperator, Variable,
-        WriteKind,
+        ArrayOperator, Atom, BinaryOperator, BinaryPlaceOperator, BindingPower, BuiltinFunction,
+        Expr, ExprNode, Getline, Place, Redirection, Ternary, UnaryOperator, UnaryPlaceOperator,
+        Variable, WriteKind,
     },
     diagnostics::ParsingError,
     lex::{SpanExt, TokenExt},
@@ -358,6 +358,13 @@ impl<'a, 'b> Pratt<'a, 'b> {
                     lex.span().since(anchor),
                 ))
             }
+        } else if next == Token::Length && !lex.peek_is(&Token::OpenParent) {
+            // POSIX: `length` without an argument list is `length($0)`.
+            Ok(Expr::node(
+                ExprNode::BuiltinCall(BuiltinFunction::Length, Vec::new_in(self.parser.arena)),
+                self.parser,
+                lex.span().since(anchor),
+            ))
         } else if let Some(builtin) = next.maps_to_builtin() {
             self.parser
                 .parse_function_call::<false>(lex, |args| ExprNode::BuiltinCall(builtin, args))
diff --git a/tests/by-util/test_awk.rs b/tests/by-util/test_awk.rs
index 3003aab..47f185f 100644
--- a/tests/by-util/test_awk.rs
+++ b/tests/by-util/test_awk.rs
@@ -982,3 +982,12 @@ fn nr_counts_across_files() {
         .succeeds()
         .stdout_is("1 1\n2 2\n3 1\n");
 }
+
+#[test]
+fn length_without_parentheses_is_length_of_record() {
+    ucmd()
+        .arg("length > 2 { print length, length / 2 } BEGIN { print length }")
+        .pipe_in("ab\nabcd\nxyz\n")
+        .succeeds()
+        .stdout_only("0\n4 2\n3 1.5\n");
+}

From 4c3e2412d00d687ffb954fa9a2707d1de6d304db Mon Sep 17 00:00:00 2001
From: Jay Hemnani <193022578+jayhemnani9910@users.noreply.github.com>
Date: Sun, 25 Oct 2026 00:15:57 +0530
Subject: [PATCH 2/2] tests: cover length(/re/) and length $1 with the bare
 length change

---
 tests/by-util/test_awk.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tests/by-util/test_awk.rs b/tests/by-util/test_awk.rs
index 47f185f..1c16d6b 100644
--- a/tests/by-util/test_awk.rs
+++ b/tests/by-util/test_awk.rs
@@ -990,4 +990,9 @@ fn length_without_parentheses_is_length_of_record() {
         .pipe_in("ab\nabcd\nxyz\n")
         .succeeds()
         .stdout_only("0\n4 2\n3 1.5\n");
+    ucmd()
+        .arg("{ print length(/b/), length $1 }")
+        .pipe_in("abc def\nxyz\n")
+        .succeeds()
+        .stdout_only("1 7abc\n1 3xyz\n");
 }