#!/bin/sh -u
# Sample solution to Unix Final Script (neat version)
#  This "neat" version is a cleaned-up version of the "sloppy" version.
#  This script is easier to maintain than the "sloppy" version.
#------------------------------------------------------------
# One line summary: compile a file and compare the source and output sizes
#------------------------------------------------------------
# Syntax:
#    $0  sourcefilename  [ outputfilename ]
#------------------------------------------------------------
# Purpose: not required for test
#-------------------------------------------------------------
# Assignment Label: not required for test
#-------------------------------------------------------------

# Step 1 - 5 marks - interpreter, one line comment, syntax, PATH, and umask
# Set a standard search path and non-restrictive umask.
#
PATH=/bin:/usr/bin ; export PATH
umask 022

#-----------------------------------------
# Input and Validation Sections
#   Normally we like to keep the Input section ahead of the Validation
#   Section; but, it seems wise to exit the script right away if the
#   first argument is bad, rather than prompting for a second argument
#   and then exiting because the first one is bad.
#-----------------------------------------

# Step 2 - 8 marks
# Exit the script if less than 1 or more than 2 arguments.
#
if [ $# -lt 1 -o $# -gt 2 ]; then
	echo 1>&2 "$0: expecting source file and optional output file,"
	echo 1>&2 "    found $# ($*)"
	exit 1
fi

# Step 3 - 2 marks
# Put the source file name (first argument) into a variable.
#
src="$1"

# Step 4 - 7 marks
# Exit if the pathname is not a plain file.
#
if [ ! -f "$src" ]; then
	echo 1>&2 "$0: C++ source '$src' is missing, inaccessible,"
	echo 1>&2 "    or not a plain file"
	exit 2
fi

# Step 5 - 7 marks
# Exit if the file is empty (zero size - contains no data).
#
if [ ! -s "$src" ]; then
	echo 1>&2 "$0: C++ source file '$src' is empty (zero size)"
	exit 3
fi

# Step 6 - 8 marks
# Read the output file name from the user if the argument is missing.
#
if [ $# -eq 2 ]; then
	out="$2"
else
    	echo 1>&2 "Enter an output file name:" 
    	read out || exit 4
fi

# Step 7 - 6 marks
# Exit if the pathname is an empty string (null string - no characters).
#
if [ -z "$out" ]; then
	echo 1>&2 "$0: Empty output file name - nothing done.  Bye!"
	exit 5
fi

#-----------------------------------------
# Processing Section
#-----------------------------------------

# Step 8 - 4 marks
# Add read permissions only for group.
#
chmod g+r "$src" || exit 6

# Step 9 - 4 marks
# Rename an existing output pathname.
#
if [ -e "$out" ]; then
	mv "$out" "backup.bak"
fi

# Step 10 - 4 marks
# Compile the C++ source into the output file with warnings enabled
#
g++ -o "$out" -Wall "$src"

# Step 11 - 4 marks
# Step 12 - 4 marks
# Step 13 - 7 marks
# Count the characters in the two files and compare the sizes.
# Tell how the size of the source file compares with the output file.
#
schars=$( wc -c <"$src" )
ochars=$( wc -c <"$out" )

if [ "$schars" -gt "$ochars" ] ; then
    diff='larger than'
elif [ "$schars" -eq "$ochars" ] ; then
    diff='the same size as'
else
    diff='smaller than'
fi

echo "source $src is $diff output $out"