I'm piping output from clock through sed to remove leading zeroes from numbers. It looks like this:

clock -sf 'S%A, %B %d. %I:%M %P' | sed 's/\b0\+\([0-9]\+\)/\1/g'

That works fine and produces the output I want.

However, when I try to redirect the output to a file, nothing is written to the file. The following does NOT work.

clock -sf 'S%A, %B %d. %I:%M %P' | sed 's/\b0\+\([0-9]\+\)/\1/g' > testfile

Nothing is written to testfile. What am I doing wrong?