August 2012
Intermediate to advanced
624 pages
17h 11m
Polish
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19.10. Usuwanie plików z użyciem pustej zmiennej
Problem
Wykorzystujemy zmienną, która zgodnie z założeniem powinna przechowywać listę plików przeznaczonych do usunięcia. Okazuje się jednak, że zmienna jest pusta, a realizacja zadania kończy się dramatycznie.
Rozwiązanie
Nigdy nie wolno stosować polecenia:
rm –rf $pliki_do_usuniecia
Nigdy, przenigdy nie wolno stosować polecenia:
rm –rf /$pliki_do_usunięcia
Zamiast nich należy korzystać z instrukcji:
[ "$plliki_do_usuniecia" ] && rm –rf $pliki_do_usuniecia
Analiza
Pierwsze polecenie nie jest aż tak złe. Po prostu generuje komunikat o błędzie. Natomiast drugie stanowi istotne zagrożenie dla systemu, gdyż może doprowadzić do usunięcia katalogu głównego. Szkody nie będą szczególnie dotkliwe, jeśli instrukcję ...
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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.