more sed stuff

from http://www.oracle.com/technology/pub/articles/dulaney_sed.html

$ cat sample_one
one 1
two 1
three 1
one 1
two 1
two 1
three 1
$

Suppose that it would be desirable for "1" to be substituted with "2," but only after the word "two" and not throughout every line. This can be accomplished by specifying that a match is to be found before giving the substitute command:

$ sed '/two/ s/1/2/' sample_one
one 1
two 2
three 1
one 1
two 2
two 2
three 1
$