grep: Add ability to output line numbers

Author: https://github.com/BenWiederhake
Commit: https://github.com/SerenityOS/serenity/commit/1d777073fd2
Pull-request: https://github.com/SerenityOS/serenity/pull/10798
Reviewed-by: https://github.com/BertalanD
Reviewed-by: https://github.com/bgianfo
Reviewed-by: https://github.com/nico

Base/usr/share/man/man1/grep.md

@@ -5,7 +5,7 @@ grep
 ## Synopsis
 
 ```sh
-$ grep [--recursive] [--extended-regexp] [--regexp Pattern] [-i] [--invert-match] [--quiet] [--no-messages] [--binary-mode ] [--text] [-I] [--color WHEN] [file...]
+$ grep [--recursive] [--extended-regexp] [--regexp Pattern] [-i] [--line-numbers] [--invert-match] [--quiet] [--no-messages] [--binary-mode ] [--text] [-I] [--color WHEN] [file...]
 ```
 
 ## Options:
@@ -16,6 +16,7 @@ $ grep [--recursive] [--extended-regexp] [--regexp Pattern] [-i] [--invert-match
 * `-E`, `--extended-regexp`: Extended regular expressions
 * `-e Pattern`, `--regexp Pattern`: Pattern
 * `-i`: Make matches case-insensitive
+* `-n`, `--line-numbers`: Output line-numbers
 * `-v`, `--invert-match`: Select non-matching lines
 * `-q`, `--quiet`: Do not write anything to standard output
 * `-s`, `--no-messages`: Suppress error messages for nonexistent or unreadable files

Userland/Utilities/grep.cpp

@@ -46,6 +46,7 @@ int main(int argc, char** argv)
     const char* pattern = nullptr;
     BinaryFileMode binary_mode { BinaryFileMode::Binary };
     bool case_insensitive = false;
+    bool line_numbers = false;
     bool invert_match = false;
     bool quiet_mode = false;
     bool suppress_errors = false;
@@ -56,6 +57,7 @@ int main(int argc, char** argv)
     args_parser.add_option(use_ere, "Extended regular expressions", "extended-regexp", 'E');
     args_parser.add_option(pattern, "Pattern", "regexp", 'e', "Pattern");
     args_parser.add_option(case_insensitive, "Make matches case-insensitive", nullptr, 'i');
+    args_parser.add_option(line_numbers, "Output line-numbers", "line-numbers", 'n');
     args_parser.add_option(invert_match, "Select non-matching lines", "invert-match", 'v');
     args_parser.add_option(quiet_mode, "Do not write anything to standard output", "quiet", 'q');
     args_parser.add_option(suppress_errors, "Suppress error messages for nonexistent or unreadable files", "no-messages", 's');
@@ -129,7 +131,7 @@ int main(int argc, char** argv)
             return 1;
         }
 
-        auto matches = [&](StringView str, StringView filename, bool print_filename, bool is_binary) {
+        auto matches = [&](StringView str, StringView filename, size_t line_number, bool print_filename, bool is_binary) {
             size_t last_printed_char_pos { 0 };
             if (is_binary && binary_mode == BinaryFileMode::Skip)
                 return false;
@@ -144,6 +146,8 @@ int main(int argc, char** argv)
                 } else {
                     if ((result.matches.size() || invert_match) && print_filename)
                         out(colored_output ? "\x1B[34m{}:\x1B[0m" : "{}:", filename);
+                    if ((result.matches.size() || invert_match) && line_numbers)
+                        out(colored_output ? "\x1B[35m{}:\x1B[0m" : "{}:", line_number);
 
                     for (auto& match : result.matches) {
                         out(colored_output ? "{}\x1B[32m{}\x1B[0m" : "{}{}",
@@ -168,11 +172,11 @@ int main(int argc, char** argv)
                 return false;
             }
 
-            while (file->can_read_line()) {
+            for (size_t line_number = 1; file->can_read_line(); ++line_number) {
                 auto line = file->read_line();
                 auto is_binary = memchr(line.characters(), 0, line.length()) != nullptr;
 
-                if (matches(line, filename, print_filename, is_binary) && is_binary && binary_mode == BinaryFileMode::Binary)
+                if (matches(line, filename, line_number, print_filename, is_binary) && is_binary && binary_mode == BinaryFileMode::Binary)
                     return true;
             }
             return true;
@@ -197,17 +201,20 @@ int main(int argc, char** argv)
             size_t line_len = 0;
             ssize_t nread = 0;
             ScopeGuard free_line = [line] { free(line); };
+            size_t line_number = 0;
             while ((nread = getline(&line, &line_len, stdin)) != -1) {
                 VERIFY(nread > 0);
                 if (line[nread - 1] == '\n')
                     --nread;
+                // Human-readable indexes start at 1, so it's fine to increment already.
+                line_number += 1;
                 StringView line_view(line, nread);
                 bool is_binary = line_view.contains(0);
 
                 if (is_binary && binary_mode == BinaryFileMode::Skip)
                     return 1;
 
-                auto matched = matches(line_view, "stdin", false, is_binary);
+                auto matched = matches(line_view, "stdin", line_number, false, is_binary);
                 did_match_something = did_match_something || matched;
                 if (matched && is_binary && binary_mode == BinaryFileMode::Binary)
                     return 0;