# Reverse content of each line.
# Casper Boden-Cummins <casper@wollery.demon.co.uk>

sed '
# add newline as a marker
G
: next
  # move char before marker to end of line
  s/\(.\)\(\n.*\)$/\2\1/

  # repeat until marker is at beginning
  t next

# remove marker
s/\n//
'