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Correct Bash and shell script variable capitalization

I run across many shell scripts with variables in all caps, and I've always thought that there is a severe misunderstanding with that. My understanding is that, by convention (and perhaps by necessity long ago), environment variables are in all-caps. ...
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What is a segmentation fault?

...ng to a read-only portion of the memory, etc. Segmentation fault is essentially the same in most languages that let you mess with the memory management, there is no principial difference between segfaults in C and C++. There are many ways to get a segfault, at least in the lower-level languages suc...
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Return value in a Bash function

...t should provide data cannot also echo other stuff to stdout, because the caller using $() will receive that too and get confused or have to parse the output. Global variables are not great because it's just a matter of time before you use the same global var in two places that happen to be nested a...
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Event system in Python

...r methods', which is a simple implementation of the Observer pattern. Basically, the handler methods (callables) are stored in an array and are each called when the event 'fires'. Publish-Subscribe The disadvantage of Observer event systems is that you can only register the handlers on the actual Ev...
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Transposing a NumPy array

...of a 1D array is still a 1D array! (If you're used to matlab, it fundamentally doesn't have a concept of a 1D array. Matlab's "1D" arrays are 2D.) If you want to turn your 1D vector into a 2D array and then transpose it, just slice it with np.newaxis (or None, they're the same, newaxis is just mor...
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Maven fails to find local artifact

Occasionally maven complains that a particular dependency, which is built and packaged locally, cannot be found in the local repository while building another project that has it as a dependency. We get an error like: ...
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Best explanation for languages without null

... that every reference type gets this extra state in its space that is typically undesired. A string variable could be any sequence of characters, or it could be this crazy extra null value that doesn't map into my problem domain. A Triangle object has three Points, which themselves have X and Y va...
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TypeError: 'str' does not support the buffer interface

...ype. In py3 plaintext is only a string, and the method outfile.write() actually takes a byte array when outfile is opened in binary mode, so an exception is raised. Change the input to plaintext.encode('utf-8') to fix the problem. Read on if this bothers you. In py2, the declaration for file.wri...
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PHP mkdir: Permission denied problem

...te permissions on the directory. Here's what you do in Ubuntu Make sure all files are owned by the Apache group and user. In Ubuntu it is the www-data group and user chown -R www-data:www-data /path/to/webserver/www Next enabled all members of the www-data group to read and write files chmod -R...
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How to change collation of database, table, column?

... You need to either convert each table individually: ALTER TABLE mytable CONVERT TO CHARACTER SET utf8mb4 (this will convert the columns just as well), or export the database with latin1 and import it back with utf8mb4. ...