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Define make variable at rule execution time
...r are evaluated. In order to create the directory only when out.tar is actually fired, you need to move the directory creation down into the steps:
out.tar :
$(eval TMP := $(shell mktemp -d))
@echo hi $(TMP)/hi.txt
tar -C $(TMP) cf $@ .
rm -rf $(TMP)
The eval function evaluates a...
Get last result in interactive Python shell
...
Underscore.
>>> 5+5
10
>>> _
10
>>> _ + 5
15
>>> _
15
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How do I use extern to share variables between source files?
...ler is informed that a
variable exists (and this is its type); it does not allocate the
storage for the variable at that point.
A variable is defined when the compiler allocates the storage for
the variable.
You may declare a variable multiple times (though once is sufficient);
you may only defin...
How to base64 encode image in linux bash / shell
...
You need to use cat to get the contents of the file named 'DSC_0251.JPG', rather than the filename itself.
test="$(cat DSC_0251.JPG | base64)"
However, base64 can read from the file itself:
test=$( base64 DSC_0251.JPG )
...
How can I save a screenshot directly to a file in Windows? [closed]
...ormat format = ImageFormat.PNG; or ImageFormat format = ImageFormat.JPG; All is here for you
– Patrick Desjardins
Oct 1 '08 at 15:31
4
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Rails: confused about syntax for passing locals to partials
...:partial => 'foo', :locals => {blah blah blah}) then it will pass in all of your arguments as a hash and parse them accordingly.
If you pass in a string as your first argument, it assumes the first argument is your partial name, and will pass the remainder as your locals. However, in that s...
Named routes _path vs _url
...
_path helpers provide a site-root-relative path. You should probably use this most of the time.
_url helpers provide an absolute path, including protocol and server name. I've found that I mainly use these in emails when cre...
How to initialize private static members in C++?
...t be done outside of any function.
Note: Matt Curtis: points out that C++ allows the simplification of the above if the static member variable is of const int type (e.g. int, bool, char). You can then declare and initialize the member variable directly inside the class declaration in the header fil...
Input and output numpy arrays to h5py
I have a Python code whose output is a sized matrix, whose entries are all of the type float . If I save it with the extension .dat the file size is of the order of 500 MB. I read that using h5py reduces the file size considerably. So, let's say I have the 2D numpy array named A . How do I ...
Why use apparently meaningless do-while and if-else statements in macros?
...into
if (corge)
f(corge); g(corge);
else
gralt();
which is syntactically incorrect, as the else is no longer associated with the if. It doesn't help to wrap things in curly braces within the macro, because a semicolon after the braces is syntactically incorrect.
if (corge)
{f(corge); g(co...