Pipeline Command for Crystal

Line by line text processor for console command mainly using with pipes('|').

Installation

Add this to your application's shard.yml:

dependencies:
  pipeline:
    github: arcage/pipeline

Usage

Inherit the Pipeline::Command class and implement #proc(line : String) method on it.

# up_case.cr
require "pipeline"

class UpCase < Pipeline::Command

  def proc(line : String)
    line.upcase
  end

end

UpCase.new.run
% crystal up_case.cr
abc def  <- INPUT
ABC DEF  <- OUTPUT
% cat input.txt
input text file
% crystal up_case.cr -- input.txt
INPUT TEXT FILE

Default input and ouput are ARGF and STDOUT respectivery.

You can specify other input or output by calling '#run' method with input or output argument.

File.open("input.txt") do |file|
  UpCase.new.run(input: file)
end

#output: INPUT TEXT FILE

Override #initialize and call super(&block), then you can set flags for the internal OptionParser object in the block.

# up_or_camel_case.cr
require "pipeline"

class UpOrCamelCase < Pipeline::Command

  def initialize
    @camelcase = false
    super() do
      # Default receiver in this block is the internal OpttionParser object.
      on("-c", "camel case") { @camelcase = true }
    end
  end

  def proc(line : String) : String
    @camelcase ? line.camelcase : line.upcase
  end

end

UpOrCamelCase.new.run
% crystal up_or_camel_case.cr
abc def  <- INPUT
ABC DEF  <- OUTPUT
^D
% crystal up_or_camel_case.cr -- -c
abc def  <- INPUT
AbcDef   <- OUTPUT
^D

Contributors