Today, bash_profile based task logger

.bash_profile.sh

# Create a log of what I did today at ~/.today
# Example:
# today I made a sandwich
# today I ate a sandwich
# cat ~/.today
# 2018-07-16 16:02:12 I made a sandwich
# 2018-07-16 15:59:28 I ate a sandwich
today(){
	# make sure the file exists
	touch ~/.today
	# get the current date/time
	DATE=`date '+%Y-%m-%d %H:%M:%S'`
	# take all of the arguments to this function and assemble them with spaces
	str="$*"
	# prepend the content to the file
	echo -e "$DATE $str\n$(cat ~/.today)" > ~/.today
}

Nice! I'm new to bash scripts, how do you get this to run? Do I source this file from bash_profile?