.bash_alias

# Helper function which takes one argument and writes the alias to file.
# Argument taken in the form nickname='commands' or nickname="commands".
setpermalias() {

	# Make sure the file exists before you continue.
	if [ ! -f $ABSPATH/.usr_aliases ]; then
		echo "File .usr_aliases does not exist. Creating."
		touch $ABSPATH/.usr_aliases
	fi

	# Define original alias in current session.
	\alias "$1"
	
	# Only proceed if the command was successful. Else leave alias' inbuilt error to tell the user what's wrong.
	if [ $? == 0 ]; then
		# Isolate nickname from alias.
		nick=`expr match "$1" '\(.*=\)'` # nick will be of form "myname="
		nick=$(echo "$nick" | tr -d '=') # nick is now alphanumeric only

		# Identify code to define this alias.
		full=$(\alias $nick)

		# Clear name definition if it already exists.  
		reg="g/^alias $nick/d\nwq\n"

		printf "$reg" | ed -s $ABSPATH/.usr_aliases > /dev/null 2>&1

		# Write new permanent alias to file.
		echo "Creating new permanent alias: $full"
		echo "$full" >> $ABSPATH/.usr_aliases
	fi
}

# Allows definition of permanent aliases. 
# Use like the alias command; use the option -s if you want to save across sessions.
# You may define multiple aliases at once.
altalias() {

	local should_save=0
	
	# Check if the -s option is enabled.
	local OPTIND opt
	while getopts "s" opt; do
		case "${opt}" in
			s) should_save=1;; 
		esac
	done

	# Iterate over all arguments.
	for arg in "$@"
	do
		if [ "$arg" != "-s" ]; then
			# If you're trying to make a permanent alias.
			if [ "$should_save" -gt 0 ]; then
				# Call helper function defined above on this arg.
				setpermalias "$arg"
			# Else do basic behavior of alias.
			else
				\alias "$arg"
			fi
		fi
	done
}

delpermalias() {
	# Unalias for current session.
	unalias "$1"
	# Check if the generated file exists
	if [ -f $ABSPATH/.usr_aliases ]; then
		# Delete the line in the file that has arg 1, the nickname. 
		sed "/^alias $1=/d" $ABSPATH/.usr_aliases
	fi
}

# Include all user-created aliases if the generated file exists. 
if [ -f $ABSPATH/.usr_aliases ]; then
	. $ABSPATH/.usr_aliases
fi