split big file on first column's value

gistfile1.sh

function splitBigFile()
{
   tail -n 1000000000 $1 | awk '{
    subNum=substr($1,length($1)-1)
    print subNum,$0
  }' | while read subNum others
  do
    echo $others >> $2.$subNum
  done
}

tail -n 10000 member_pv.tmp | awk '{a=$1%100; print $0 > "mid_"a".txt"}'