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Test if remote TCP port is open from a shell script
... > /dev/tcp/sfsfdfdff.com/80'
bash: sfsfdfdff.com: Name or service not known
bash: /dev/tcp/sfsfdfdff.com/80: Invalid argument
$ echo $?
1
# Connection not established by the timeout
$ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/google.com/81'
$ echo $?
124
What's happening here is tha...
Git - Pushing code to two remotes [duplicate]
...riginal/repo.git
remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
Now, if you want to push to two or more repositories using a single command, you may create a new remote named all (as suggested by @Adam Nelson in comments), or keep using the origin, though the latter name is less descripti...
Anaconda vs. EPD Enthought vs. manual installation of Python [closed]
...
Update 2015: Nowadays I always recommend Anaconda. It includes lots of Python packages for scientific computing, data science, web development, etc. It also provides a superior environment tool, conda, which allows to easily switch betwee...
Python assigning multiple variables to same value? list behavior
...t element of a to 1, the first elements of b and c are 1.
If you want to know if two names are naming the same object, use the is operator:
>>> a=b=c=[0,3,5]
>>> a is b
True
You then ask:
what is different from this?
d=e=f=3
e=4
print('f:',f)
print('e:',e)
Here, you'r...
Proper way to renew distribution certificate for iOS
...l of my provisioning files. How do I properly renew it? Should I revoke it now and request a new one? If I do that than will all my live apps be taken down?
...
Can I embed a custom font in an iPhone application?
...:
Custom Font Support
Applications that want to use custom fonts can now include those fonts in their application bundle and register those fonts with the system by including the UIAppFonts key in their Info.plist file. The value of this key is an array of strings identifying the font files in...
What are enums and why are they useful?
...s (contract status: "permanent", "temp", "apprentice"), or flags ("execute now", "defer execution").
If you use enums instead of integers (or String codes), you increase compile-time checking and avoid errors from passing in invalid constants, and you document which values are legal to use.
BTW, o...
Difference between timestamps with/without time zone in PostgreSQL
...ly in the docs. The difference arises from what the system can reasonably know about the value:
With a time zone as part of the value, the value can be rendered as a local time in the client.
Without a time zone as part of the value, the obvious default time zone is UTC, so it is rendered for that...
What's the difference between passing by reference vs. passing by value?
...by value vs. pass by reference" distinction as defined in the CS theory is now obsolete because the technique originally defined as "pass by reference" has since fallen out of favor and is seldom used now.1
Newer languages2 tend to use a different (but similar) pair of techniques to achieve the sam...
Is it smart to replace boost::thread and boost::mutex with c++11 equivalents?
...1 timeouts are different to Boost timeouts (though this should soon change now Boost.Chrono has been accepted).
Some of the names are different (e.g. boost::unique_future vs std::future)
The argument-passing semantics of std::thread are different to boost::thread --- Boost uses boost::bind, which re...