Before everyone starts modifying their programs, modifying all their print statements, I'd like to point old and trusty cat. Everyone knows cat. Not everyone knows its options. -E is very useful in this regard: it makes cat print a $ at the end of each line. Other useful cat options for debugging output: -T which displays tabs as ^I, and -v which will show non-printable and non-ASCII characters using ^ and M- notation. With some versions of cat,
cat -vET can also be written as cat -A.
in reply to Unbelievably Obvious Debugging Tip
cat is your friend. Never debug without it!