August 2012
Intermediate to advanced
624 pages
17h 11m
Polish
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5.17. Generowanie komunikatów o błędach w przypadku niezdefiniowania parametrów
Problem
Przedstawione wcześniej rozwiązania mające na celu wyznaczanie wartości domyślnych są bardzo przydatne, ale niekiedy działanie skryptu jest uzależnione od tego, czy użytkownik wprowadzi pewną wartość, czy nie. Czasami nieuwzględnienie parametrów sprawia, że użytkownicy nie wiedzą, jakie zadania są w rzeczywistości realizowane przez skrypt. Załóżmy, że zgadywanie nie jest wskazane. Czy istnieje jakaś szybsza metoda sprawdzenia wartości kilku parametrów niż definiowanie grupy instrukcji if?
Rozwiązanie
W odwołaniach do parametrów można wykorzystać zapis ${:?}. Jeżeli parametr nie jest zdefiniowany lub ma pustą wartość, powłoka bash wygeneruje stosowny komunikat ...
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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.
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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.