interpreter: count NR across files and keep the last record for END

interpreter/src/vm/io.rs

@@ -58,23 +58,37 @@ impl From<&[u8]> for FilePath {
 }
 
 impl Interpreter<'_> {
-    pub fn begin_file_prelude(&mut self, f: Option<&Path>, res: Option<&io::Error>) {
+    pub fn begin_file_prelude(
+        &mut self,
+        f: Option<&Path>,
+        res: Option<&io::Error>,
+        has_begin_file: bool,
+    ) {
         let name = f.map_or(b"-".as_slice(), |p| p.as_os_str().as_encoded_bytes());
         let errno = res.map_or(0, |e| e.raw_os_error().unwrap_or(-1) as _);
 
         self.symbols.filename = Value::new_string(name.into());
         self.symbols.errno = Value::new_int(errno);
         self.symbols.fnr = Value::new_int(0);
-        self.record.clear();
+        // Like gawk, BEGINFILE never sees the previous file's last record.
+        // Without BEGINFILE, $0 survives an empty last file for END.
+        if has_begin_file {
+            self.record.clear();
+        }
     }
 
     // TODO: consider caching the result of all this validation, so we can
     // directly dispatch to the correct functions and avoid extra writes to RT.
     // TODO: on Windows, we must strip `\r` depending on BINMODE.
-    pub fn read_record(&mut self, reader: impl BufRead) -> Result<bool> {
+    pub fn read_record(&mut self, mut reader: impl BufRead) -> Result<bool> {
+        // At EOF, keep NR, FNR and $0 of the last record for END
+        if reader.fill_buf()?.is_empty() {
+            return Ok(false);
+        }
+
         // Update vars
         // TODO: optimize and make more ergonomic
-        self.symbols.nr = &self.symbols.fnr + &Value::new_int(1);
+        self.symbols.nr = &self.symbols.nr + &Value::new_int(1);
         self.symbols.fnr = &self.symbols.fnr + &Value::new_int(1);
 
         let rs = self.symbols.rs.clone();

src/event.rs

@@ -79,8 +79,9 @@ impl<'a> AwkRt<'a> {
         path: Option<&Path>,
         res: Option<&io::Error>,
     ) -> Result<bool> {
-        self.intrp.begin_file_prelude(path, res);
-        match self.drive(self.bc.begin_file_code())? {
+        let code = self.bc.begin_file_code();
+        self.intrp.begin_file_prelude(path, res, !code.is_empty());
+        match self.drive(code)? {
             CtrlSig::End => Ok(false),
             CtrlSig::NextFile => Ok(true),
             CtrlSig::Exit(code) => self.end_event_loop(code).map(|_| false),
@@ -106,7 +107,12 @@ impl<'a> AwkRt<'a> {
 
     pub fn rule_event_loop(&mut self) -> Result<()> {
         let range = self.bc.rules_code();
-        if range.is_empty() {
+        // Input is read unless the program has only BEGIN rules
+        if range.is_empty()
+            && self.bc.end_code().is_empty()
+            && self.bc.begin_file_code().is_empty()
+            && self.bc.end_file_code().is_empty()
+        {
             return Ok(());
         }
 

tests/by-util/test_awk.rs

@@ -908,3 +908,77 @@ fn slash_after_special_variable_divides() {
         .succeeds()
         .stdout_only("0.5 2\n1 1\n2\n3\n");
 }
+
+#[test]
+fn end_sees_last_record() {
+    ucmd()
+        .arg(r"{ s += $2 } END { print NR, FNR, $0, s / NR }")
+        .pipe_in("a 1\nb 2\nc 6\n")
+        .succeeds()
+        .stdout_is("3 3 c 6 3\n");
+}
+
+#[test]
+fn end_only_program_reads_input() {
+    ucmd()
+        .arg("END { print NR, $1 }")
+        .pipe_in("a\nb\n")
+        .succeeds()
+        .stdout_is("2 b\n");
+}
+
+#[test]
+fn end_after_empty_file() {
+    let ts = uutests::util::TestScenario::new("awk");
+    ts.fixtures.write("a", "x y\nlast z\n");
+    ts.fixtures.write("empty", "");
+    ts.cmd(crate::TESTS_BINARY)
+        .args(&["END { print NR, FNR, \"[\" $0 \"]\", NF }", "empty"])
+        .succeeds()
+        .stdout_is("0 0 [] 0\n");
+    ts.cmd(crate::TESTS_BINARY)
+        .args(&["END { print NR, FNR, \"[\" $0 \"]\", NF }", "a", "empty"])
+        .succeeds()
+        .stdout_is("2 0 [last z] 2\n");
+}
+
+#[test]
+fn beginfile_does_not_see_previous_record() {
+    let ts = uutests::util::TestScenario::new("awk");
+    ts.fixtures.write("a", "x y\nlast z\n");
+    ts.fixtures.write("b", "w\n");
+    ts.fixtures.write("empty", "");
+    ts.cmd(crate::TESTS_BINARY)
+        .args(&["BEGINFILE { print FILENAME, \"[\" $0 \"]\", NF }", "a", "b"])
+        .succeeds()
+        .stdout_is("a [] 0\nb [] 0\n");
+    // gawk clears $0 for BEGINFILE, so END after an empty last file sees it empty
+    ts.cmd(crate::TESTS_BINARY)
+        .args(&[
+            "BEGINFILE { n++ } END { print n, \"[\" $0 \"]\", NF }",
+            "a",
+            "empty",
+        ])
+        .succeeds()
+        .stdout_is("2 [] 0\n");
+}
+
+#[test]
+fn end_after_missing_trailing_newline() {
+    ucmd()
+        .arg(r#"END { print NR, FNR, "[" $0 "]", NF }"#)
+        .pipe_in("p\nq r")
+        .succeeds()
+        .stdout_is("2 2 [q r] 2\n");
+}
+
+#[test]
+fn nr_counts_across_files() {
+    let ts = uutests::util::TestScenario::new("awk");
+    ts.fixtures.write("a", "x\ny\n");
+    ts.fixtures.write("b", "z\n");
+    ts.cmd(crate::TESTS_BINARY)
+        .args(&["{ print NR, FNR }", "a", "b"])
+        .succeeds()
+        .stdout_is("1 1\n2 2\n3 1\n");
+}