For those wanting to make sure their script is Bourne Shell compatible but you don’t have actual Bourne Shell available, Heirloom Bourne Shell is something you may want to look into – comes in source package, no configure script, you just have to edit very simple modifications to very simple Makefile, compile and install and you have Bourne Shell with NO extensions whatsoever – with that I’ve learned a lot on how much imagination and crazy hacks you may have to achieve to do things that in Bash are quite normal things to do It may be fun, I for one like to do some hobby projects “just to see if I can” where I try to do something in Bourne Shell – like transforming script relying on recursive function calls into Bourne Shell which has no function local variables, only script global ones (hint: subprocess inside function can help, of course the things you can do are limited, subprocess can have it’s own variables, but you can’t change variables outside it, he-he).

PS. There’s no need for ‘-p “”‘, it should default to a blank prompt

n=0 # n being the number of (valid) data provided
sum=0 # sum being the running total of all data

# “Note that by using ^D (aka “EOF”) to quit, this script will work just as well blah blah”
# — Thanks, so i can make a function out of this and pipe data directly into it =)

function calc_avg() {
while read -p “” x; do
sum=`expr $sum + $x` && n=$[n+1] # “expr” return status indicates if valid integer or not
done

# ok, finished adding, now calculate the average.
echo “scale=2;$sum/$n” | bc
}

# like said above, just pipe $* args through calc_avg with a newline between each one.
echo $* | tr ‘ ‘ ‘\n’ | calc_avg

### TODO: write a version that accepts floating point numbers as arguments ###

what about

$ awk ‘{ sum += $1} END {print sum/NR}’ /path/to/data.txt

These days, most *nix boxes have Bash available, but /bin/sh still points to the Bourne shell. Indeed, Debian is going back from /bin/sh being bash, to dash. Ubuntu has already replaced /bin/sh with dash.

http://release.debian.org/lenny/goals.txt

Steve

#!/bin/sh
n=0
sum=0
while read x
do
sum=$(( $sum + $x ))
if [ "$?" -eq "0" ]; then
(( n += 1 ))
fi
done
echo “$(echo “scale=2;$sum/$n” | bc) $n”

The last command, bc, is changed a bit to also show the number of elements in the average.

Time to average 10000 items:
OLD: 25.76s
NEW: 0.44s (440ms)

#!/bin/sh
n=0
sum=0
while read x
do
sum=`echo $sum + $x|bc`
if [ "$?" -eq "0" ]; then
n=`expr $n + 1`
fi
done
echo “scale=2;$sum/$n” | bc