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What does -D_XOPEN_SOURCE do/mean?

...t;some number> it tells your compiler to include definitions for some extra functions that are defined in the X/Open and POSIX standards. This will give you some extra functionality that exists on most recent UNIX/BSD/Linux systems, but probably doesn't exist on other systems such as Windows. ...
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How to ignore xargs commands if stdin input is empty?

... may take advantage of -L <#lines>, -n <#args>, -i, and -I <string>: ls /empty_dir/ | xargs -n10 chown root # chown executed every 10 args or fewer ls /empty_dir/ | xargs -L10 chown root # chown executed every 10 lines or fewer ls /empty_dir/ | xargs -i cp {} {}.bak # every {} is ...
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Is there a way to ignore header lines in a UNIX sort?

... after the end of the first line. If you run it on a pipe, bash reads one char at a time until it passes the end of the line. – Sam Watkins May 5 '15 at 9:01 ...
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C# Events and Thread Safety

...ith every event - aka boilerplate code! public event Action<thisClass, string> Some; protected virtual void DoSomeEvent(string someValue) { var e = Some; // avoid race condition here! if(null != e) // avoid null condition here! e(this, someValue); } 2 - the race condition issue) ...
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In Python, what happens when you import inside of a function? [duplicate]

...me is expensive. Try running an empty script vs one containing just import string,itertools,fractions,heapq,re,array,bisect,collections,math,os. The first takes an average of 180 ms, and the second 230 ms. So it's not microseconds for starters. It's tens of milliseconds (maybe a disc access happens?...
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PHP: Storing 'objects' inside the $_SESSION

...on objects based on the ID the client submitted with the request. All this extra work is a double whammy on scalability (a big reason HTTP is stateless). Whammy One: It reduces the work a single server can do. Whammy Two: It makes it harder to scale out because now you can't just route a request t...
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How to stop C++ console application from exiting immediately?

... Edit: As Charles Bailey rightly points out in a comment below, this won't work if there are characters buffered in stdin, and there's really no good way to work around that. If you're running with a debugger attached, John Dibling's ...
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How can I get a list of Git branches, ordered by most recent commit?

... Great alias! I would suggest column -ts'|' and pipe characters if the comma char can occur inside relative timestamps in your locale. – Björn Lindqvist
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What is the difference between RDF and OWL? [closed]

...edicate. The object is either another URI or a literal such as a number or string. Literals can have a type (which is also a URI), and they can also have a language. Yes, this means triples can have up to 5 bits of data! For example a triple might describe the fact that Charles is Harrys father. &...
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HTML entity for the middle dot

... There's actually six variants of this: char description unicode html html entity utf-8 · Middle Dot U+00B7 · · C2 B7 • Bullet U+2022 • • ...