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$ sed "s/\(^[a-z,0-9]*\)\(.*\)\( [a-z,0-9]*$\)/\1\2 \1/g" desired_file_name

I apreciate it even if you only explain part of it or at lest structure it with words as in s\alphanumerical_at_start\something\alphanumerical_at_end\something_else\global

Could someone explain what that means, why and are all regEx so ... awful ?

I know that it replaces the first lowcase alphanumerical word with the last one. But could you explain bit by bit what's going on here ? what's with all the /\ and \(.*\)\ and everything else ?

I'm just lost.

EDIT: Here is what I do get: (^[a-z0-9]*) starting with a trough z and 0 trough 9; and [a-z,0-9]*$ is the same but the last word (however [0-9,a-z] = just first 2 characters / first character, or the entire word ?). Also: what does the * or the \(.*\)\ even mean ?

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closed as off topic by hhlp, fossfreedom Jun 5 '12 at 17:15

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Question isn't suited to this SE site. Try stackoverflow.com –  jackweirdy Jun 5 '12 at 16:36
    
I understand. I thought it being linux this is the place, sorry about that. And here I have tags for both regEx and sed ... they seem to be there also, so I'll give it a shot –  Kalec Jun 5 '12 at 16:45
    
askubuntu is (or at least aims to be) specific to Ubuntu. RegEx can apply to lots of operating systems and programming languages so it doesn't fit here –  jackweirdy Jun 5 '12 at 17:31

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