#replace : with new line
echo $PATH|tr ":" "\n" #equivalent with:
echo $PATH|tr -t ":" \n 

#complement "aa"
echo aabbccd |tr -c "aa" 1
#output: aa11111%
#tip: Complement meaning keep aa,all other is replace with 1

#complement "ab\n"
echo aabbccd |tr -c "ab\n" 1
#output: aabb111 with new line

#Preserve all alpha(-c). ":-[:digit:] etc" will translate to "\n". sequeeze mode.
echo $PATH|tr -cs "[:alpha:]" "\n" 

#ordered list to unordered list
echo "1 /usr/bin\n2 /bin" |tr -cs "/\n[:alpha:]" "+"

#remove all occurance of "ab"
echo aabbcc |tr -d "ab"