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Another one I can't seem to solve : all greek letters with 5 unique letters (meaning that each letter only appears once).

my solution :

egrep '(.)([^/1])([^/1/2])([^/1/2/3])([^/1/2/3/4])' greek.txt

So What I think I am saying :

  • match any first character

  • every consecutive character can't be any of the previous patterns

But what comes out :

alpha
gamma
delta
epsilon
theta
kappa
lambda
omicron
sigma
upsilon
omega

Alpha, gamma, they have characters that are not unique. Any hints or tips on what I am doing wrong ?

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1 Answer 1

I think you're on the right track but got your slashes going to wrong direction to be back-references. Use \1 not /1!

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indeed, backrefs are \1 and not /1 –  Goez Aug 8 '11 at 12:44
    
still not working unfortunately :( –  Lucas Kauffman Aug 8 '11 at 13:24
    
I'll have a look when I get home... –  Goez Aug 8 '11 at 13:41
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