expr: fix regex matching on inputs containing newlines (#10543)

Author: ChrisDryden

src/uu/expr/src/syntax_tree.rs

@@ -354,15 +354,15 @@ fn build_regex(pattern_bytes: Vec<u8>) -> ExprResult<(Regex, String)> {
             // For UTF-8 locale, use UTF-8 encoding
             Regex::with_options_and_encoding(
                 &re_string,
-                RegexOptions::REGEX_OPTION_SINGLELINE,
+                RegexOptions::REGEX_OPTION_SINGLELINE | RegexOptions::REGEX_OPTION_MULTILINE,
                 Syntax::grep(),
             )
         }
         UEncoding::Ascii => {
             // For non-UTF-8 locale, use ASCII encoding
             Regex::with_options_and_encoding(
                 EncodedBytes::ascii(re_string.as_bytes()),
-                RegexOptions::REGEX_OPTION_SINGLELINE,
+                RegexOptions::REGEX_OPTION_SINGLELINE | RegexOptions::REGEX_OPTION_MULTILINE,
                 Syntax::grep(),
             )
         }
@@ -427,7 +427,7 @@ fn find_match(regex: Regex, re_string: String, left_bytes: Vec<u8>) -> ExprResul
                 // Need to create ASCII version of regex too
                 let re_ascii = Regex::with_options_and_encoding(
                     EncodedBytes::ascii(re_string.as_bytes()),
-                    RegexOptions::REGEX_OPTION_SINGLELINE,
+                    RegexOptions::REGEX_OPTION_SINGLELINE | RegexOptions::REGEX_OPTION_MULTILINE,
                     Syntax::grep(),
                 )
                 .ok();

tests/by-util/test_expr.rs

@@ -457,6 +457,14 @@ fn test_regex_range_quantifier() {
         .stderr_only("expr: Invalid content of \\{\\}\n");
 }
 
+#[test]
+fn test_regex_newline() {
+    new_ucmd!()
+        .args(&["line1\nline2\nline3 ", ":", ".*line2.*"])
+        .succeeds()
+        .stdout_only("18\n");
+}
+
 #[test]
 fn test_substr() {
     new_ucmd!()