section6.sh

#!/bin/bash

EXERCISE_NUMBER=0
TOTAL_ALLOWED_EXERCISE=2

# Exercise 1:
# Write a shell script that renames all files in the current directory that end in ".jpg" to begin with
# today's date in the following format: YYYY­MM­DD. For example, if a picture of my cat was in
# the current directory and today was October 31, 2016 it would change name from "mycat.jpg" to
# "2016­10­31­mycat.jpg".
# Hint: Look at the format options to the date command.
# For "extra credit" make sure gracefully handle instances where there are no ".jpg" files in the
# current directory. (Hint: Man bash and read the section on the nullglob option.)
function e1() {
	shopt -s nullglob
	local DATE_PREFIX=$(date +%Y%m%d)
	[ $? -ne 0 ] && echo "No file found" ;
	for i in `ls *.jpg`;
		do cp $i $DATE_PREFIX$i;
	done
}




# Exercise 2:
# Write a script that renames files based on the file extension. The script should prompt the user
# for a file extension. Next, it should ask the user what prefix to prepend to the file name(s). By
# default the prefix should be the current date in YYYY­MM­DD format. So, if the user simply
# presses enter the date will be used. Otherwise, whatever the user entered will be used as the
# prefix. Next, it should display the original file name and the new name of the file. Finally, it
# should rename the file.
# Example output 1:
# Please enter a file extension: jpg
# Please enter a file prefix: (Press ENTER for 2015­08­10). vacation
# Renaming mycat.jpg to vacation­mycat.jpg.
# Example output 2:
# Please enter a file extension: jpg
# Please enter a file prefix: (Press ENTER for 2015­08­10).
# Renaming mycat.jpg to 2015­08­10­mycat.jpg.
function e2() {
	read -p "Please enter a file extension: " FILE_EXTENSION
	read -p "Please enter a file prefix: (Press ENTER for 20160209) " PREFIX
	for i in `ls *.$FILE_EXTENSION`; do
		[ -z $PREFIX ] && PREFIX=`date +%Y%m%d`
		local new_file_name=$PREFIX$i
		echo "Renaming $i to $new_file_name"
		cp $i $new_file_name
	done
}

function run() {
	if [ $# -ne 1 ]
	then
		echo "No exercise selected!"
		read -p "Please pass in the exercise number[1-2]: " EXERCISE_NUMBER
	else
		EXERCISE_NUMBER=$1
    fi
	run_exercise $EXERCISE_NUMBER
}

function run_exercise() {
	if [ "$1" -le "$TOTAL_ALLOWED_EXERCISE" ]
		then 
			FUNCTION_NAME="e$1"
			$FUNCTION_NAME
    else
    	echo "Wrong exercise number passed: "$1
    fi
}
run $@