how to write command line pipeline in ruby

I would like to create a shell-script like pipeline using command line commands in ru开发者_StackOverflowby. So I have a few steps in the pipeline, each step is a command line like commands (using a particular tool and the usual input and output files, like run xtool -i xx -o xxx).

Thanks in advance

Mark

You can run external programs by quoting with backticks or using %x:

x = `echo "hello"`
y = %x{echo "hello"}

You can look at the last process through $?:

`rm an_existing_file`
$?.exitstatus # now: o

`rm missing_file`
$?.exitstatus # now: 1

If you need to do anything more complex, look at the Ruby Process Docs.

Hard to know what you are asking, but if you want to write a Ruby command-line app that can be used in a pipeline on the command line, but also possibly use command-line arguments, you can do this:

require 'optparse'

input = STDIN
output = STDOUT
option_parser = OptionParser.new do |opts|
  options.on("-i FILE","Input file (defaults to stdin)") do |filename|
    input = File.new(filename)
  end
  options.on("-o FILE","Output file (defaults to stdout)") do |filename|
    output = File.new(filename,'w')
  end
end

option_parser.parse!

input.readlines.each do |line|
  # do something with line
  output.puts "Some awesome output"
end
output.close # NOTE, this must be the last line of your program since
             # you are possibly closing the standard output

You also have sh and system kernel methods. You can write your own shell script and invoke it using system('yourscript.sh').

system returns true if the command gives zero exit status, false otherwise.