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How to get the start time of a long-running Linux process?
...ticks since system boot.1
This is a slightly tricky unit to use; see also convert jiffies to seconds for details.
awk -v ticks="$(getconf CLK_TCK)" 'NR==1 { now=$1; next }
END { printf "%9.0f\n", now - ($20/ticks) }' /proc/uptime RS=')' /proc/12345/stat
This should give you seconds, which yo...
Numbering rows within groups in a data frame
...g this approach, make sure that you are not getting conflicts between plyr and dplyr as explained in this post It can be avoided by explicitly calling dplyr::mutate(...)
– EcologyTom
Apr 10 '18 at 14:16
...
How can I beautify JavaScript code using Command Line?
...cutefoo.js
uglify uses spaces for indentation by default so if I want to convert the 4-space-indentation to tabs I can run it through unexpand which Ubuntu 12.04 comes with:
unexpand --tabs=4 cutefoo.js > cuterfoo.js
Or you can do it all in one go:
uglifyjs foo.js --beautify | unexpan...
Difference between freeze and seal
...rn false
It makes every existing property non-configurable: they cannot be converted from 'data descriptors' to 'accessor descriptors' (and vice versa), and no attribute of accessor descriptors can be modified at all (whereas data descriptors can change their writable attribute, and their value attr...
Comparing two dataframes and getting the differences
... lists, to do it efficiently we should first order them then compare them (converting the list to sets/hashing would also be fast; both are an incredible improvement to the simple O(N^2) double comparison loop
Note: the following code produces the tables:
df1=pd.DataFrame({
'Date':['2013-11-24...
Why does appending “” to a String save memory?
...owing:
data.substring(x, y) + ""
creates a new (smaller) String object, and throws away the reference to the String created by substring(), thus enabling garbage collection of this.
The important thing to realise is that substring() gives a window onto an existing String - or rather, the charac...
Laravel Check If Related Model Exists
...$relation) is a general solution for all relations. It will work for Model and Collection, while Model has no ->count() method.
– Jarek Tkaczyk
Jul 29 '14 at 17:16
8
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MySQL: @variable vs. variable. What's the difference?
...are loosely typed variables that may be initialized somewhere in a session and keep their value until the session ends.
They are prepended with an @ sign, like this: @var
You can initialize this variable with a SET statement or inside a query:
SET @var = 1
SELECT @var2 := 2
When you develop a stor...
JavaScript + Unicode regexes
...mall Java program that uses its own native Unicode support).
Basically it converts \p{...} to a range of values, much like the output of the tool mentioned by Tomalak, but the intervals can end up quite large (since it's not dealing with blocks, but with characters scattered through many different ...
How do I implement an Objective-C singleton that is compatible with ARC?
How do I convert (or create) a singleton class that compiles and behaves correctly when using automatic reference counting (ARC) in Xcode 4.2?
...