#!/bin/bash

# This program computes the median of a list of integers on the command line.
# If there are no arguments, then it asks the user to enter them on
# separate lines.  Then it prints the median (middle
# value after sorting).  If there are an even number of numbers, then
# the median is the average of the 2 middle values, rounding down

# Copy the command line into array n
i=0  # current element of n
finished=0  # 1 (true) when there is no more interactive input expected
while (($# > 0)); do
  ((n[i] = $1))
  shift
  ((i++))
  finished=1
done

# Else if there are no arguments then ask the user to enter some numbers
if ((!finished)); then
  echo Enter some numbers, one per line.  Enter a blank line when done.
  while ((!finished)); do
    read x
    if [ "$x" == "" ]; then
      finished=1
    else
      ((n[i++]=x))
    fi
  done
fi

# If n is empty then give up
size=${#n[*]}
if ((size==0)); then
  echo Error: at least one number is expected
  exit 1
fi

# Bubble sort n
((i=size-1))
while ((i>0)); do
  j=0
  while ((j<i)); do
    if ((n[j]>n[j+1])); then  #swap so n[j] <= n[j+1]
      ((t=n[j]))
      ((n[j]=n[j+1]))
      ((n[j+1]=t))
    fi
    ((++j))
  done
  ((--i))
done

# Compute the median from the middle 1 or 2 elements
((mid = size/2))
if ((size  % 2 == 0)); then
  ((median = (n[mid] + n[mid-1]) / 2))
else
  ((median = n[mid]))
fi

# Print the sorted array and the median
echo The median of ${n[*]} is $median