tr1

tr

echo 12345 | tr '0-9' '9876543210'

echo 87654 | tr '9876543210' '0-9'

ROT13

echo "tr came, tr saw, tr conquered." | tr 'a-zA-Z' 'n-za-mN-ZA-M'

echo ge pnzr, ge fnj, ge pbadhrerq. | tr 'a-zA-Z' 'n-za-mN-ZA-M'

tr ' ' ' ' < file.txt

tr -d  #delete char

cat file.txt | tr -d '[set1]'

e.g. 

echo "Hello 123 world 456" | tr -d '0-9'

tr -c

tr -s '[string]'

echo 'GNU is    not     UNIX . Recursive   right  ?' | tr -s ' '

  cat file.txt | tr -s ' '

tr [:class:] [:class:]

tr ' [:lower:]' '[:upper:]'

tr

alnum

alpha

cntrl

digit

graph

lower

print

punct

space

upper

xdigit