File: sed.info,  Node: wc -w,  Next: wc -l,  Prev: wc -c,  Up: Examples

7.14 Counting Words
===================

This script is almost the same as the previous one, once each of the
words on the line is converted to a single ‘a’ (in the previous script
each letter was changed to an ‘a’).

   It is interesting that real ‘wc’ programs have optimized loops for
‘wc -c’, so they are much slower at counting words rather than
characters.  This script's bottleneck, instead, is arithmetic, and hence
the word-counting one is faster (it has to manage smaller numbers).

   Again, the common parts are not commented to show the importance of
commenting ‘sed’ scripts.

     #!/usr/bin/sed -nf

     # Convert words to a's
     s/[ ][ ]*/ /g
     s/^/ /
     s/ [^ ][^ ]*/a /g
     s/ //g

     # Append them to hold space
     H
     x
     s/\n//

     # From here on it is the same as in wc -c.
     /aaaaaaaaaa/! bx;   s/aaaaaaaaaa/b/g
     /bbbbbbbbbb/! bx;   s/bbbbbbbbbb/c/g
     /cccccccccc/! bx;   s/cccccccccc/d/g
     /dddddddddd/! bx;   s/dddddddddd/e/g
     /eeeeeeeeee/! bx;   s/eeeeeeeeee/f/g
     /ffffffffff/! bx;   s/ffffffffff/g/g
     /gggggggggg/! bx;   s/gggggggggg/h/g
     s/hhhhhhhhhh//g
     :x
     $! { h; b; }
     :y
     /a/! s/[b-h]*/&0/
     s/aaaaaaaaa/9/
     s/aaaaaaaa/8/
     s/aaaaaaa/7/
     s/aaaaaa/6/
     s/aaaaa/5/
     s/aaaa/4/
     s/aaa/3/
     s/aa/2/
     s/a/1/
     y/bcdefgh/abcdefg/
     /[a-h]/ by
     p