#!/bin/bash 
bins=3
bin=1
seed=$RANDOM
while [ `echo $1 | grep "-"` ]; do
	case $1 in
		-B|--bins) bins=$2;;
		-b|--bin) bin=$2;;
		-s|--seed) seed=$2;;
		-h|--help) cat <<-EOF
			someArff : divide an arrf file into Bins, create train/test files 	
			usage: someArff [flags] arffFile
			Flags
		  	-B, --bins NUM   Randomly divide the data into NUM bins
		  	-b, --bin  NUM   Store bin NUM into test.arff and rest into train.arff
		  	-s, --seed NUM   Set the random number seed to NUM
		  	-h, --help       Print this text
			EOF
			return 1;;
		*)   blabln "'"$1"' unknown\n usage cat file | someArff [options]"
		     return 1;;
    	esac
	shift 2
done
gawk '
	BEGIN  { 
	 	 IGNORECASE=1;
	         Trainf="train.arff"; Testf="test.arff"; 
      		 Bins=3; 
		 Bin=1; 
	         Seed=1;
	       } 
	 /^[ \t]*$/          { next }
	 /@relation/         { Seed ? srand(Seed) : srand(1)      }
	 /@relation/         { printf "">Trainf;  printf "">Testf }
	 /@relation/,/@data/ { print $0 >> Trainf;  print $0 >> Testf; next }
         { Line[rand()] = $0; Lines++ }
  	END { 
		Start = Lines/Bins * (Bin - 1) ;
		Stop  = Lines/Bins * Bin;
		for(I in Line) {
			N++;
			What = (N>= Start && N < Stop) ? Testf : Trainf
			print Line[I]>>What; }
		}' Seed=$seed Bins=$bins Bin=$bin -