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

Space or end of line? Use |:

s/ \([mt]\)\( \|$\)/\1\2/g

Answer 2

Just matching space, then m or t, then space or newline won't catch cases with punctuation, e.g. a missing ' in "please don t!". A more general solution is to use word boundaries instead:

echo "i m sure he doesn t test test don t." | sed 's/ \([mt]\)[[:>:]]/\1/g'

The funky [[:>:]] is required on OS X (which I use), see Larry Gerndt's answer to sed whole word search and replace. On other sed flavors you may be able to use \b (any word boundary) or \> instead.

# example with word boundary
echo "i m sure he doesn t test test don t." | sed 's/ \([mt]\)[[:>:]]/\1/g'
im sure he doesnt test test dont.

Answer 3

Make last space optional:

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

Posix friendly version:

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