ROT13/ROT47 is an example of the Caesar cipher, developed in ancient Rome. Unix command. tr transliterate

ROT13.sh

# encode 
tr 'A-Za-z' 'N-ZA-Mn-za-m' <<<"The Quick Brown Fox Jumps Over The Lazy Dog"

# decode
echo "Gur Dhvpx Oebja Sbk Whzcf Bire Gur Ynml Qbt" | tr '[A-Za-z]' '[N-ZA-Mn-za-m]'

ROT47.sh

$ tr '\!-~' 'P-~\!-O' <<<"The Quick Brown Fox Jumps Over The Lazy Dog"