replacing word after multiple spaces

Question

I need to replace a word after multiple spaces :

actually the file contains this string :

local   all             all                                         


        

Answer 1

Am I missing some part of this problem? I made a file with the first line above as contents, then ran the simplest possible sed command on it ... and came out with the 2nd line.

~ >cat test.txt
local   all             all                                     peer

~ >sed 's/peer/md5/g' test.txt
local   all             all                                     md5

works fine with multiple lines as well ...

~ >cat test.txt
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
~ >sed 's/peer/md5/g' test.txt
local   all             all                                     md5
local   all             all                                     md5
local   all             all                                     md5
local   all             all                                     md5
local   all             all                                     md5
local   all             all                                     md5

The only time this will not work is if the word "peer" shows up somewhere else on a line where you do not want it replaced with md5 ...

This one replaces only the first occurance of the search term:

~ >cat test.txt
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
~ >sed '0,/peer/s//md5/' test.txt
local   all             all                                     md5
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer
local   all             all                                     peer