#! /bin/bash
#copy c programs to $HOME/backup directory
if    test ! -d $HOME/backup 
then
 echo $HOME/backup not exist
 mkdir $HOME/backup
 echo ... $HOME/backup created
fi
for i in *.c
do
if  test ! -f $HOME/backup/$i 
# or [  ]  make sure you leave spaces at each side.
#if  [ ! -f $HOME/backup/$i ] 
then
	echo $i not in $HOME/backup
	cp $i $HOME/backup/$i
	echo copied $i to $HOME/backup/$i
else
	echo comparing $i with $HOME/backup/$i
	if  cmp -s $i $HOME/backup/$i
	then
       		echo .... identical...
	else
		echo .... different...copying $i to $HOME/backup/$i
		cp $i $HOME/backup/$i
	fi
fi
done