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How to call an external command?
How do you call an external command (as if I'd typed it at the Unix shell or Windows command prompt) from within a Python script?
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Test for non-zero length string in Bash: [ -n “$var” ] or [ “$var” ]
...t, I'll use [ ! "$var" ] instead of [ -z "$var" ].
– AllenHalsey
Oct 6 '10 at 20:32
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What is the correct SQL type to store a .Net Timespan with values > 24:00:00?
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There isn't a direct equivalent. Just store it numerically, e.g. number of seconds or something appropriate to your required accuracy.
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How to use double or single brackets, parentheses, curly braces
...veral more
Also, brace expansions create lists of strings which are typically iterated over in loops:
$ echo f{oo,ee,a}d
food feed fad
$ mv error.log{,.OLD}
(error.log is renamed to error.log.OLD because the brace expression
expands to "mv error.log error.log.OLD")
$ for num in {000..2}; do ech...
Do NSUserDefaults persist through an Update to an app in the Appstore?
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They are usually not reset unless the user deletes the app. For basic data, NSUserDefaults is the best way to save data such as preferences, dates, strings etc. If you are looking to save images and files, the file system is a better bet...
How to loop through file names returned by find?
... # Not recommended, will break on whitespace
process "$i"
done
Marginally better, cut out the temporary variable x:
for i in $(find -name \*.txt); do # Not recommended, will break on whitespace
process "$i"
done
It is much better to glob when you can. White-space safe, for files in the ...
What does the -ObjC linker flag do?
...braries that contain categories on existing classes.
From this Technical Q&A
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Is there any async equivalent of Process.Start?
Like the title suggests, is there an equivalent to Process.Start (allows you run another application or batch file) that I can await?
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Convert an image to grayscale in HTML/CSS
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For posterity: @TomAuger, this Q&A has specific instructions for IE10.
– Barney
Sep 25 '14 at 10:32
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Are arrays passed by value or passed by reference in Java? [duplicate]
...a primitive type in Java, but they are not objects either ... "
In fact, all arrays in Java are objects1. Every Java array type has java.lang.Object as its supertype, and inherits the implementation of all methods in the Object API.
... so are they passed by value or by reference? Does it de...