UNIX for Dummies Questions & Answers

#!/usr/bin/env ksh
# add a value to the array
function add_value
{
    typeset i=0

    i=${#values[@]}             # current length
    if (( $i >= $nvalues ))     # cap at nvalues
    then
        i=$(( $nvalues - 1 ))
    fi
    for (( ; i > 0; i-- ))          # shift values up in the array
    do
        values[$i]=${values[$(($i-1))]}
    done

    values[0]=$1            # add the new value
}

# compute the mean
function mean
{
    typeset i=0
    typeset sum=0

    if (( ${#values[@]} < 1 ))   # prevent divide by zero accidents
    then
        echo 0
        return
    fi

    for (( i = 0; i < ${#values[@]}; i++ ))
    do
        sum=$(( ${values[$i]} + sum ))
    done

    echo $(( sum / ${#values[@]} ))
}

nvalues=5               # max number of values to maintain

add_value 25            # add values to the list
add_value 2
add_value 23
mean                    # compute mean at any time if needed
add_value 42   
add_value 43
add_value 44

mean                    # compute mean
exit