Using U+ notation instead of M- for non-printing characters.

README.md

@@ -3,7 +3,7 @@
 
 # dcat: Concatenate File(s) to Standard Output
 
-A **cat** command-line implemenation in [Dart](https://dart.dev/), inspired by the [Write command-line apps sample code](https://dart.dev/tutorials/server/cmdline).
+A **cat** command-line implementation in [Dart](https://dart.dev/), inspired by the [Write command-line apps sample code](https://dart.dev/tutorials/server/cmdline).
 
 ## Synopsis
 
@@ -30,7 +30,7 @@ With no FILE, or when FILE is -, read standard input.
   -T, --show-tabs                display TAB characters as ^I
   -s, --squeeze-blank            suppress repeated empty output lines
       --version                  output version information and exit
-  -v, --show-nonprinting         use ^ and M- notation, except for LFD and TAB
+  -v, --show-nonprinting         use ^ and U+ notation, except for LFD and TAB
 
 Examples:
   dcat f - g  Output f's contents, then standard input, then g's contents.
@@ -51,4 +51,5 @@ dart compile exe bin/dcat.dart
 ## Differences from [GNU cat](https://www.gnu.org/software/coreutils/manual/html_node/cat-invocation.html#cat-invocation)
   - No binary file support.
   - A line is considered terminated by either a `CR` (carriage return), a `LF` (line feed), a `CR+LF` sequence (DOS line ending).
-  - The non-printing `M-^?` notation is always used for unicode characters.
+  - A line ending is automatically appended to the last line of any read file.
+  - The `U+` notation is used instead of `M-` for non-printing characters.

bin/dcat.dart

@@ -57,7 +57,7 @@ Future<int> main(List<String> arguments) async {
   parser.addFlag(showNonPrintingFlag,
       negatable: false,
       abbr: 'v',
-      help: 'use ^ and M- notation, except for LFD and TAB');
+      help: 'use ^ and U+ notation, except for LFD and TAB');
 
   final ArgResults argResults;
   try {

doc/api/index.html

@@ -47,7 +47,7 @@
   <p><a href="http://opensource.org/licenses/BSD-3-Clause"><img src="https://img.shields.io/badge/license-BSD%203--Clause-blue.svg?style=flat-square" alt="License (3-Clause BSD)"></a>
 <a href="https://github.com/ethauvin/dcat/actions/workflows/dart.yml"><img src="https://github.com/ethauvin/dcat/actions/workflows/dart.yml/badge.svg" alt="GitHub CI"></a></p>
 <h1 id="dcat-concatenate-files-to-standard-output">dcat: Concatenate File(s) to Standard Output</h1>
-<p>A <strong>cat</strong> command-line implemenation in <a href="https://dart.dev/">Dart</a>, inspired by the <a href="https://dart.dev/tutorials/server/cmdline">Write command-line apps sample code</a>.</p>
+<p>A <strong>cat</strong> command-line implementation in <a href="https://dart.dev/">Dart</a>, inspired by the <a href="https://dart.dev/tutorials/server/cmdline">Write command-line apps sample code</a>.</p>
 <h2 id="synopsis">Synopsis</h2>
 <p><strong>dcat</strong> copies each file, or standard input if none are given, to standard output.</p>
 <h2 id="command-line-usage">Command-Line Usage</h2>
@@ -68,7 +68,7 @@ With no FILE, or when FILE is -, read standard input.
   -T, --show-tabs                display TAB characters as ^I
   -s, --squeeze-blank            suppress repeated empty output lines
       --version                  output version information and exit
-  -v, --show-nonprinting         use ^ and M- notation, except for LFD and TAB
+  -v, --show-nonprinting         use ^ and U+ notation, except for LFD and TAB
 
 Examples:
   dcat f - g  Output f's contents, then standard input, then g's contents.
@@ -85,7 +85,8 @@ Examples:
 <ul>
 <li>No binary file support.</li>
 <li>A line is considered terminated by either a <code>CR</code> (carriage return), a <code>LF</code> (line feed), a <code>CR+LF</code> sequence (DOS line ending).</li>
-<li>The non-printing <code>M-^?</code> notation is always used for unicode characters.</li>
+<li>A line ending is automatically appended to the last line of any read file.</li>
+<li>The <code>U+</code> notation is used instead of <code>M-</code> for non-printing characters.</li>
 </ul>
 </section>
 

lib/dcat.dart

@@ -83,18 +83,7 @@ Future<String> _parseNonPrinting(String line, bool showTabs) async {
       } else if (ch == 127) {
         sb.write('^?');
       } else {
-        sb.write('M-');
-        if (ch >= 128 + 32) {
-          if (ch < 128 + 127) {
-            sb.writeCharCode(ch - 128);
-          } else {
-            sb.write('^?');
-          }
-        } else {
-          sb
-            ..write('^')
-            ..writeCharCode(ch - 128 + 64);
-        }
+          sb.write('U+' +  ch.toRadixString(16).padLeft(4, '0').toUpperCase());
       }
     } else if (ch == 9 && !showTabs) {
       sb.write('\t');

test/dcat_test.dart

@@ -1,4 +1,6 @@
-import 'dart:io';
+// Copyright (c) 2021, Erik C. Thauvin. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be found
+// in the LICENSE file.
 
 import 'package:dcat/dcat.dart';
 import 'package:test/test.dart';
@@ -129,13 +131,13 @@ void main() {
     test('Test cat -A', () async {
       await cat(['test/test.txt'],
           log: log, showNonPrinting: true, showEnds: true, showTabs: true);
-      expect(log.last, equals('^I^A^B^C^DM-)^?M-^@M-^?\$'));
+      expect(log.last, equals('^I^A^B^C^DU+00A9^?U+0080U+2713\$'));
     });
 
     test('Test cat -t', () async {
       await cat(['test/test.txt'],
           log: log, showNonPrinting: true, showTabs: true);
-      expect(log.last, equals('^I^A^B^C^DM-)^?M-^@M-^?'));
+      expect(log.last, equals('^I^A^B^C^DU+00A9^?U+0080U+2713'));
     });
 
     test('Test cat-Abs', () async {
@@ -156,8 +158,7 @@ void main() {
     });
 
     test('Test cat -v', () async {
-      await cat(['test/test.txt'],
-          log: log, showNonPrinting: true);
+      await cat(['test/test.txt'], log: log, showNonPrinting: true);
       var hasTab = false;
       for (final String line in log) {
         if (line.contains('\t')) {
@@ -166,6 +167,8 @@ void main() {
         }
       }
       expect(hasTab, true, reason: "has real tab");
+      expect(log.last, equals('\t^A^B^C^DU+00A9^?U+0080U+2713'),
+          reason: 'non-printing');
     });
   });
 }