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

A Dart command-line and library implementation of the standard cat Unix utility, inspired by the Write command-line apps sample code.

Synopsis

dcat sequentially reads files, or standard input if none are given, writing them 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
  -v, --show-nonprinting         use ^ and M- notation, except for LFD and TAB
      --version                  output version information and exit

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

Linux / MacOS

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

Windows

dart compile exe bin/dcat.dart

Library Usage

dart pub add dcat

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 error in result.errors) {
    print('Error: ${error.message}');
  }
}

View Full Instructions

The cat function supports the following parameters:

Parameter	Description	Type
paths	The file paths.	String[]
output	The standard output or file.	IOSink
input	The standard input.	Stream
showEnds	Same as -e	bool
numberNonBlank	Same as -b	bool
showLineNumbers	Same as -n	bool
showTabs	Same as -T	bool
squeezeBlank	Same as -s	bool
showNonPrinting	Same as -v	bool

• paths and output are required.
• output should be an IOSink such as 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 errors, if any:

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

View Full Example