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How to check if a variable is set in Bash?
How do I know if a variable is set in Bash?
33 Answers
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Useless use of cat?
This is probably in many FAQs - instead of using:
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What is the explanation for these bizarre JavaScript behaviours mentioned in the 'Wat' talk for Code
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Here's a list of explanations for the results you're seeing (and supposed to be seeing). The references I'm using are from the ECMA-262 standard.
[] + []
When using the addition operator, both the left and right operands are convert...
Java logical operator short-circuiting
Which set is short-circuiting, and what exactly does it mean that the complex conditional expression is short-circuiting?
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What is the purpose of the var keyword and when should I use it (or omit it)?
What exactly is the function of the var keyword in JavaScript, and what is the difference between
19 Answers
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What is the relationship between Looper, Handler and MessageQueue in Android?
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A Looper is a message handling loop: it reads and processes items from a MessageQueue. The Looper class is usually used in conjunction with a HandlerThread (a subclass of Thread).
A Handler is a utility class that facilitates interac...
What is an “unwrapped value” in Swift?
I'm learning Swift for iOS 8 / OSX 10.10 by following this tutorial , and the term " unwrapped value " is used several times, as in this paragraph (under Objects and Class ):
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How is Python's List Implemented?
Is it a linked list, an array? I searched around and only found people guessing. My C knowledge isn't good enough to look at the source code.
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How do you effectively model inheritance in a database?
...ch class which derives from it has its own table, with a primary key which is also a foreign key to the base class table; the derived table's class contains only the different elements.
So for example:
class Person {
public int ID;
public string FirstName;
public string LastName;
}
cl...
Lock, mutex, semaphore… what's the difference?
...A lock allows only one thread to enter the part that's locked and the lock is not shared with any other processes.
A mutex is the same as a lock but it can be system wide (shared by multiple processes).
A semaphore does the same as a mutex but allows x number of threads to enter, this can be used ...