Vi: Search and Replace

Change to normal mode with <ESC>.

Search (Wraped around at end of file):

Search STRING forward :   / STRING.

Search STRING backward:   ? STRING.

Repeat search:   n

Repeat search in opposite direction:  N  (SHIFT-n)

Replace: Same as with sed, Replace OLD with NEW:

First occurrence on current line:      :s/OLD/NEW

Globally (all) on current line:        :s/OLD/NEW/g 

Between two lines #,#:                 :#,#s/OLD/NEW/g

Every occurrence in file:              :%s/OLD/NEW/g