editing with regular expressions in linux?

Alex_is · 11-18-2009, 05:58 AM

if i have created a file consisting of lines, with say four words per line separated by a space, andsay i typed this command into vi;

:%s/\(\a\+\)\s*\(\a\+\)\s*\(\a\+\)\s*\(\a\+\)/\4-\3-\2-\1/

what would this command do to the file and how would it work exactly. i am very new to linux and have tried to understand the question but cannot. i dont have access to a linux machine until next week so cant try it. plz help!

druuna · 11-18-2009, 06:22 AM

Hi,

First: This looks a lot like homework to me, so I'll just give a partial answer. It is up to you to figure out how this command works.

The end result will be: the four words in reverse with a dash (-) in between.

aaaaa bbbbb ccccc ddddd -> ddddd-ccccc-bbbbb-aaaaa

Take a look at this sed page, it holds all the answers you are looking for:
sed tutorial

Hope this helps.