August 2012
Intermediate to advanced
624 pages
17h 11m
Polish
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14.7. Wyznaczenie bezpiecznej wartości $IFS
Problem
Chcemy mieć pewność, że wartość zmiennej środowiskowej $IFS, czyli zmienna wewnętrznego separatora pól, jest właściwie zdefiniowana.
Rozwiązanie
Na początku każdego skryptu zmienna powinna otrzymać poprawną, znaną wartość. Służy do tego poniższe polecenie (niezgodne ze specyfikacją POSIX):
# Ustawienie bezpiecznej wartości IFS (składnia dla powłok bash i ksh93 - nieprzenośna!) IFS=$' \t\n'
Analiza
Zgodnie z dołączonym do kodu komentarzem przedstawiona składnia nie jest przenośna. Niestety standardowa (przenośna) składnia instrukcji nie gwarantuje ustawienia właściwych wartości — treść wiersza może zostać zniekształcona przez edytory, które usuwają krańcowe znaki odstępu. Wartościami separatora są zazwyczaj ...
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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.