dcat: Concatenate File(s) to Standard Output or File

A cat command-line and library implementation in Dart, inspired by the Write command-line apps sample code.

Synopsis

dcat copies each file, or standard input if none are given, to standard output or file.

Command-Line Usage

dcat --help

Usage: dcat [OPTION]... [FILE]...
Concatenate FILE(s) to standard output.

With no FILE, or when FILE is -, read standard input.

  -A, --show-all                 equivalent to -vET
  -b, --number-nonblank          number nonempty output lines, overrides -n
  -e, --show-nonprinting-ends    equivalent to -vE
  -E, --show-ends                display $ at end of each line
  -h, --help                     display this help and exit
  -n, --number                   number all output lines
  -t, --show-nonprinting-tabs    equivalent to -vT
  -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 U+ notation, except for LFD and TAB

Examples:
  dcat f - g  Output f's contents, then standard input, then g's contents.
  dcat        Copy standard input to standard output.

Compile Standalone Application

*nix

dart compile exe -o bin/dcat bin/dcat.dart

Windows

dart compile exe bin/dcat.dart

Library Usage

import 'package:dcat/dcat.dart';

final result = await cat(['path/to/file', 'path/to/otherfile]'],
    File('path/to/outfile').openWrite());
if (result.isFailure) {
  for (final message in result.messages) {
    print("Error: $message");
  }
}

The cat function supports the following parameters:

• paths and output are required.
• output should be an IOSink like stdout or a File stream.
• input can be stdin.

The remaining optional parameters are similar to the GNU cat utility.

A CatResult object is returned which contains the exitCode (exitSuccess or exitFailure) and error messages if any:

final result = await cat(['path/to/file'], stdout);
if (result.exitCode == exitSuccess) {
  ...
} else {
  for (final message in result.messages) {
    stderr.writeln("Error: $message");
  }
}

Differences from GNU cat

• No binary file support.
• The U+ notation is used instead of M- for non-printing characters.