August 2012
Intermediate to advanced
624 pages
17h 11m
Polish
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8.5. Usuwanie zduplikowanych wierszy
Problem
Po wyodrębnieniu i (lub) posortowaniu danych na listingu wynikowym występuje wiele wierszy o jednakowej treści. Trzeba pozbyć się duplikatów i pozostawić w zestawieniu jedynie wartości unikatowe.
Rozwiązanie
Do dyspozycji mamy dwa rozwiązania. Jeśli zestawienie podlega sortowaniu, wystarczy dodać do polecenia sort opcję –u:
$ sekwencja_poleceń | sort –uJeżeli instrukcja sortująca nie jest wykorzystywana, ale dane są wstępnie posortowane (wiersze o jednakowej treści sąsiadują ze sobą), można za pomocą potoku przekazać treść listingu do polecenia uniq.
$ sekwencja_poleceń | uniqAnaliza
Ponieważ polecenie uniq wymaga dostarczenia wstępnie posortowanych danych, zazwyczaj korzystniejszym rozwiązaniem okazuje się ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.