tr

commas to newlines

cat file.txt | tr , "\n" 

wipe all whitespace including newlines

cat file.txt | tr -d " \t\n\r" 

remove spaces

cat file.txt | tr -d "[:space:]"

or

cat file.txt | tr -d " "

in order to wipe just horizontal white space

cat file.txt | tr -d "[:blank:]"