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Check if a string has white space
... "/" characters are sufficient.
/^\s+$/ is checking whether the string is ALL whitespace:
^ matches the start of the string.
\s+ means at least 1, possibly more, spaces.
$ matches the end of the string.
Try replacing the regex with /\s/ (and no quotes)
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Count all occurrences of a string in lots of files with grep
...a bunch of log files. I need to find out how many times a string occurs in all files.
15 Answers
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How can I add a help method to a shell script?
... into a shell script? I would like to display a help message when a user calls myscript.sh -h .
6 Answers
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JPA: How to have one-to-many relation of the same Entity type
...em.persist(daughter);
em.getTransaction().commit();
}
In this case, all three entity instances must be persisted before transaction commit. If I fail to persist one of the entities in the graph of parent-child relationships, then an exception is thrown on commit(). On Eclipselink, this is a...
'IF' in 'SELECT' statement - choose output value based on column values
...tp://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html.
Additionally, you could handle when the condition is null. In the case of a null amount:
SELECT id,
IF(type = 'P', IFNULL(amount,0), IFNULL(amount,0) * -1) as amount
FROM report
The part IFNULL(amount,0) means when amount ...
How to duplicate virtualenv
...is to use pip to generate a requirements file. A requirements file is basically a file that contains a list of all the python packages you want to install (or have already installed in case of file generated by pip), and what versions they're at.
To generate a requirements file, go into your origin...
Find size of object instance in bytes in c#
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First of all, a warning: what follows is strictly in the realm of ugly, undocumented hacks. Do not rely on this working - even if it works for you now, it may stop working tomorrow, with any minor or major .NET update.
You can use th...
Canary release strategy vs. Blue/Green
...old until someone flips a feature toggle. Breaking your application into small, independently releaseable services is another, since there is less to test and less that can break.
You need to do a canary release if you're not completely certain that the new version will function correctly in produc...
Check if a div exists with jquery [duplicate]
...re using jQuery I don't see any reason to use getElementById, unless you really need the performance improvement (e.g. it's in a long loop or something, though I can't think of how this would come up, that you need to run thousands of select queries over and over). It's just much more verbose, over ...
What is the use case of noop [:] in bash?
... to do.
while keep_waiting; do
: # busy-wait
done
The : builtin dates all the way back to the Thompson shell, it was present in Unix v6. : was a label indicator for the Thompson shell's goto statement. The label could be any text, so : doubled up as a comment indicator (if there is no goto comm...