Sed regexp looking for either whitespace or end of line

Question

I\'m trying to detect a pattern that has three parts:

1. A space
2. Either an \"m\" or a \"t\"
3. Either a space or the end of a line

I

Answer 1

Make last space optional:

sed 's/[ ]\([mt][ ]\?\)$/\1/' input

Posix friendly version:

sed 's/[ ]\([mt][ ]\{,1\}\)$/\1/' input