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What is a regular expression for a MAC Address?
...at" comes from Wikipedia, not the 802.3 standards body. IEEE 802-2014 actually specifies hyphens for ordinary MAC addresses (§ 8.1 ¶ 3) and colons for the obsolescent bit-reversed notation (¶ 4). Importantly, in practice, no one observes this. We simply use one or the other, but never mix them...
Inputting a default image in case the src attribute of an html is not valid?
...body>
</html>
Since the first image doesn't exist, the fallback (the sprites used on this web site*) will display. And if you're using a really old browser that doesn't support object, it will ignore that tag and use the img tag. See caniuse website for compatibility. This element...
How to set proxy for wget?
...
For all users of the system via the /etc/wgetrc or for the user only with the ~/.wgetrc file:
use_proxy=yes
http_proxy=127.0.0.1:8080
https_proxy=127.0.0.1:8080
or via -e options placed after the URL:
wget ... -e use_proxy=ye...
How can I merge two commits into one if I already started rebase?
...7d8b496ea00d5488481db5 a
That is, a was the first commit, then b, and finally c. After committing c we decide to squash b and c together:
(Note: Running git log pipes its output into a pager, less by default on most platforms. To quit the pager and return to your command prompt, press the q key.)...
Including a groovy script in another groovy
...ble quotes with your groovy script).
I do this with a class surprisingly called "Tools.groovy".
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Which commit has this blob?
... scripts take the blob’s SHA1 as the first argument, and after it, optionally, any arguments that git log will understand. E.g. --all to search in all branches instead of just the current one, or -g to search in the reflog, or whatever else you fancy.
Here it is as a shell script – short and sw...
Invalidating JSON Web Tokens
...s an emergency, or a user token was compromised, one thing you could do is allow the user to change an underlying user lookup ID with their login credentials. This would render all associated tokens invalid, as the associated user would no longer be able to be found.
I also wanted to note that it is...
Using LIMIT within GROUP BY to get N results per group?
...
You could use GROUP_CONCAT aggregated function to get all years into a single column, grouped by id and ordered by rate:
SELECT id, GROUP_CONCAT(year ORDER BY rate DESC) grouped_year
FROM yourtable
GROUP BY id
Result:
---------------------------------------------------...
Is the practice of returning a C++ reference variable evil?
...
In general, returning a reference is perfectly normal and happens all the time.
If you mean:
int& getInt() {
int i;
return i; // DON'T DO THIS.
}
That is all sorts of evil. The stack-allocated i will go away and you are referring to nothing. This is also evil:
int& get...
How to rename a single column in a data.frame?
...r.name'
This code pretty much does the following:
names(df) looks into all the names in the df
[names(df) == old.var.name] extracts the variable name you want to check
<- 'new.var.name' assigns the new variable name.
...