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How to check if an email address exists without sending an email?
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VRFY user
You can issue a RCPT, and see if the mail is rejected.
MAIL FROM:<>
RCPT TO:<user@domain>
If the user doesn't exist, you'll get a 5.1.1 DSN. However, just because the email is not rejected, does not mean the user exists. Some server will silently discard requests like t...
Explain the concept of a stack frame in a nutshell
...atter it has loaded the local variables or not, it will immediately return from stack with it's stack frame. It means that whenever any recursive function get base condition satisfied and we put a return after base condition, the base condition will not wait to load local variables which are located...
How to pipe list of files returned by find command to cat to view all the files
...ys the contents of all those files) and basically need to grep something from these files.
15 Answers
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how to delete all cookies of my website in php
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PHP setcookie()
Taken from that page, this will unset all of the cookies for your domain:
// unset cookies
if (isset($_SERVER['HTTP_COOKIE'])) {
$cookies = explode(';', $_SERVER['HTTP_COOKIE']);
foreach($cookies as $cookie) {
$par...
How to check whether a variable is a class or not?
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That was taken from the inspect module so I doubt it doesn't work. It's simple to check with Python2.7 for example In [8]: class NewStyle(object): ...: pass ...: In [9]: isinstance(NewStyle, (type, types.ClassType)) ...
performSelector may cause a leak because its selector is unknown
...round. Here's how:
if (!_controller) { return; }
SEL selector = NSSelectorFromString(@"someMethod");
IMP imp = [_controller methodForSelector:selector];
void (*func)(id, SEL) = (void *)imp;
func(_controller, selector);
Or more tersely (though hard to read & without the guard):
SEL selector =...
Why can't we have static method in a (non-static) inner class?
.... I want to write a utility inner class. Some of its methods would benefit from access to the outer class, so I can't make it static, but some of its methods are just utility functions. Why can't I call A.B.sync(X) or even (from within A) B.sync(x)?
– Edward Falk
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Detect permission of camera in iOS
... if you are testing code that uses this, you can't merely delete your App from the testing device and then re-instal. Doing this will not cause iOS to reissue the request to the user! What's worked for me though is to change the Bundle ID of the app each time I want to test this. A pain in the bum, ...
How do I find the time difference between two datetime objects in python?
...conds, 60)
(0, 8) # 0 minutes, 8 seconds
Subtracting the later time from the first time difference = later_time - first_time creates a datetime object that only holds the difference.
In the example above it is 0 minutes, 8 seconds and 562000 microseconds.
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Why are mutable structs “evil”?
...e around.
If your struct is immutable then all automatic copies resulting from being passed by value will be the same.
If you want to change it you have to consciously do it by creating a new instance of the struct with the modified data. (not a copy)
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