Given a list of numbers separated by newlines, prints out a histogram.

histogram.sh

#!/bin/bash

NUMTESTS=0
histogram=()

while read num
do
  ((NUMTESTS++))
  ((histogram[num]++))
done

maxIndex=0
maxCount=0

for index in ${!histogram[*]}
do
  if ((index>maxIndex))
  then
    maxIndex=$index
  fi

  if ((histogram[index]>maxCount))
  then
    maxCount=${histogram[index]}
  fi
done

for ((i=maxCount; i>0; i--))
do
  printf '%3d' $i
  for ((j=0; j<=maxIndex; j++))
  do
    if ((histogram[j] >= i))
    then
      printf ' # '
    else
      printf '   '
    fi
  done
  echo
done

echo -n '   '
for ((j=0; j<=maxIndex; j++))
do
  printf '%2d ' $j
done