Add up a column of numbers at the Unix shell

Question

Given a list of files in files.txt, I can get a list of their sizes like this:

cat files.txt | xargs ls -l | cut -c 23-30

which pr

Answer 1

Here goes

cat files.txt | xargs ls -l | cut -c 23-30 | 
  awk '{total = total + $1}END{print total}'