shell script: grab

grab

#!/usr/bin/env ruby

if STDIN.tty?
  def print_help
    puts <<-EOT.gsub(/^\s+\|/, '')
      |Usage: ls | grab <column number>
      |       grab <column number> < INFILE
      |       grab <column number> <column number2> <column number3> ... < INFILE
      |
      |grab outputs a specific column of content from STDIN.
      |
      |  column number - the numeric index of the column you want
      |        to output. This is 1-based Not 0-based.
      |
      |Example #1: Grabbing the filename from ls -l
      |  ls -l | grab 9
      |
      |Example #2: Grabbing the list of modified file names in your Git index
      |  git status | grep modified: | grab 3
      |
      |Example #3: Grabbing multiple columns
      |  ls -l | grab 1 9
      |
      |Author: Zach Dennis ([email protected], [email protected])
      |        http://www.continuousthinking.com
      |        http://www.mutuallyhuman.com
    EOT
  end

  if ["-h", "--help"].include?(ARGV.first)
    print_help
    exit 0
  else
    print_help
    exit 1
  end
else
  # we are 1-based, so convert to 0-based
  columns = ARGV.map { |i| i.to_i - 1 }

  arr = STDIN.readlines.map{ |line|
    columns.map{ |column_index|
      line.split(/\s+/)[column_index].to_s
    }
  }

  maxlengths = []

  columns.each { |column_index|
    arr.each { |data|
      length = 0
      data.each_with_index { |cdata, i|
        maxlengths[i] = cdata.length if cdata.length > length
      }
    }
  }

  arr.each do |data|
    data.each_with_index do |cdata, i|
      printf "%-#{maxlengths[i]}s\t", cdata
    end
    puts
  end
end