Unix-function-like Ruby Script

script_ruby.rb

#!/usr/bin/env ruby

require 'getoptlong'

version        = "0.0.1" # used by the --version or -v option handler
extract_f      = false   # set to true when --extract or -e are used
extract_args   = []      # stores the list of arguments of --extract or -e
remove_f       = false   # set to true when --remove or -r are used
remove_args    = []      # stores the list of arguments of --remove or -r
ex_options_n   = 0       # used to store the number of mutually exclusive
                         # options, when > 1, the script will terminate
have_options_f = false   # set to true when at least one option is used 

def printusage(error_code)
  print "csvt -- extract columns of data from a CSV (Comma-Separate Values) file\n"
  print "Usage: csvt [POSIX or GNU style options] file ...\n\n"
  print "POSIX options                     GNU long options\n"
  print "    -e col[,col][,col]...             --extract col[,col][,col]...\n"
  print "    -r col[,col][,col]...             --remove col[,col][,col]...\n"
  print "    -h                                --help\n"
  print "    -u                                --usage\n"
  print "    -v                                --version\n\n"

  print "Examples: \n"
  print "csvt -e 1,5,6 file            print column 1,5 and 6 from file\n"
  print "csvt --extract 4,1 file       print column 4 and 1 from file\n"
  print "csvt -r 2,7,1 file            print all columns except 2,7 and 1 from file\n"
  print "csvt --remove 6,0 file        print all columns except 6 and 0 from file\n"
  print "cat file | csvt --remove 6,0  print all columns except 6 and 0 from file\n\n"
  print "Send bugs reports to bugs@foo.bar\n"
  print "For licensing terms, see source code\n"
  exit(error_code)
end

opts = GetoptLong.new(
  [ "--extract",     "-e",   GetoptLong::REQUIRED_ARGUMENT ],
  [ "--remove",      "-r",   GetoptLong::REQUIRED_ARGUMENT ],
  [ "--help",        "-h",   GetoptLong::NO_ARGUMENT ],
  [ "--usage",       "-u",   GetoptLong::NO_ARGUMENT ],
  [ "--version",     "-v",   GetoptLong::NO_ARGUMENT ]
)

begin
  opts.each do |opt, arg|
    case opt
      when "--extract"
        extract_f    = true
        extract_args = arg.split(",")

        tmp = 0
        extract_args.each do |column|
          begin
            extract_args[tmp] = Integer(column)
            tmp += 1
          rescue
            $stderr.print "csvt: non-integer column index\n"
            printusage(1)
          end
        end

        ex_options_n   += 1
        have_options_f  = true
      when "--remove"
        remove_f    = true
        remove_args = arg.split(",")

        tmp = 0
        remove_args.each do |column|
          begin
            remove_args[tmp] = Integer(column)
            tmp += 1
          rescue
            $stderr.print "csvt: non-integer column index\n"
            printusage(1)
          end
        end

        ex_options_n   += 1
        have_options_f  = true
      when "--help"
        printusage(0)
      when "--usage"
        printusage(0)
      when "--version"
        print "csvt, version ", version, "\n"
        exit(0)
    end
  end

  #################################################################
  # test for mutually exclusive options: --extract and --remove

  if ex_options_n > 1
    $stderr.print "csvt: cannot use --extract (-e) and --remove (-r) together\n"
    printusage(1)
  end

  #################################################################
  # test for missing options 

  if have_options_f == false
    printusage(1)
  end

rescue 
  printusage(1)
end