Biodegradable Geek

This Bash script is used to calculate your Grade Point Average (GPA) on the command line. Usage might not be intuitive. Please see the usage function or just run the script without passing it any arguments.

The gval function should be edited to reflect your own region or university. It has been written and tested on Bash 3.2.48.

#!/bin/sh
#
# Bash GPA calculator
#
# Isam | r0cketjump@yahoo.com | biodegradablegeek.com
# 05/21/2009 - Just another 4 AM project

function usage {
  echo -e "\nBASH GPA Calculator"
  echo
  echo -e "\tAccepts an even # of arguments in the form of C G C G C G ..."
  echo -e "\t (C = number of credits, G = grade for the course)"
  echo
  echo -e "\tExample: You got a B+ in a 4 credit course, "
  echo -e "\t         an A in a 3 credit course, etc.."
  echo
  echo -e "\tUSAGE: $0 4 B+ 3 A 3 F 3 B-"
  echo
  echo "Acceptable grades are A B C D F WU (eq to F)"
  echo
}

function calc {
  echo `echo "scale=3; $1" | bc`
}

function gval {
  grade=`echo "$1" | tr [a-z] [A-Z]`
  case $grade in
    A+ ) echo '4.3';;
    A ) echo '4';;
    A- ) echo '3.7';;

    B+ ) echo '3.3';;
    B ) echo '3.00';;
    B- ) echo '2.7';;

    C+ ) echo '2.3';;
    C ) echo '2.0';;
    C- ) echo '1.7';;

    D+ ) echo '1.3';;
    D ) echo '1.0';;
    D- ) echo '0.7';;

    F ) echo '0';;
    WF ) echo '0';;
    WU ) echo '0';;
  esac
}

# check # of arguments. is it even?
let MOD=$#%2
if [ ! $MOD -eq 0 ]; then
  usage
  exit
elif [ $# -eq 0 ]; then
  usage
  exit
fi

args=($@)
n=${#args[@]}

points=0
credits=0

for ((i=0;i<$n-1;i+=2)); do
  k=${i}

  creds=${args[$k]}
  cgrade=${args[$k+1]}

  # convert cgrade (C-) to a number
  grade=`gval $cgrade`
  pts=`calc $grade*$creds`

  echo "$creds * $cgrade ($grade) = $pts"

  points=`calc $points+$pts`
  credits=`calc $credits+$creds`
done

gpa=`calc $points/$credits`
echo "------------"
echo "Total points  = $points"
echo "Total credits = $credits"
echo "------------"
echo "** GPA (pts/crd) = $gpa"
echo "------------"

(Script uses bc as the calculator. Change that in the calc function if you need to.)

I’ll never get used to Bash’s ugly ass syntax. … esac?
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