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ruby system command check exit code
...d execution fails.
system("unknown command") #=> nil
system("echo foo") #=> true
system("echo foo | grep bar") #=> false
Furthermore
An error status is available in $?.
system("VBoxManage createvm --invalid-option")
$? #=> #<Process::Status: pid 9...
Check if a temporary table exists and delete if it exists before creating a temporary table
...te to say that double dot is the default schema of the user, which is typically dbo (which isn't a great idea, making dbo the default schema for users but that's usually how it goes)
– jcollum
Oct 22 '14 at 17:45
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(Built-in) way in JavaScript to check if a string is a valid number
...
A very important note about parseInt is that it will allow you to specify a radix for converting the string to an int. This is a big gotcha as it tries to guess a radix for you if you don't supply it. So, for example: parseInt("17") results in 17 (decimal, 10), but parseInt("...
disable textbox using jquery?
... value = $(this).val();
if(value == 'x'){
enableInput('foo'); //with class foo
enableInput('bar'); //with class bar
}else{
disableInput('foo'); //with class foo
disableInput('bar'); //with class bar
}
});
});
...
How can I get the ID of an element using jQuery?
...'#test').prop('id')
which is different from .attr() and $('#test').prop('foo') grabs the specified DOM foo property, while $('#test').attr('foo') grabs the specified HTML foo attribute and you can find more details about differences here.
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When to use Vanilla JavaScript vs. jQuery?
... there are certain practices using javascript, instead of jQuery, that actually enable you to write less and do ... well the same amount. And may also yield performance benefits.
...
Isn't “package private” member access synonymous with the default (no-modifier) access?
...package. As a concrete example :
package ab;
class A {
protected void foo() {}
void dd(){}
}
class C {
void aa(){
A a = new A();
a.foo(); //legal
a.dd(); //legal
}
}
package sub;
class D extends A{
void ac(){
foo(); //legal ..
dd(); //...
Is it possible to make a type only movable and not copyable?
...of a value is a byte copy:
let x: T = ...;
let y: T = x; // byte copy
fn foo(z: T) -> T {
return z // byte copy
}
foo(y) // byte copy
They are byte copies whether or not T moves or is "implicitly copyable". (To be clear, they aren't necessarily literally byte-by-byte copies at run-time: ...
How to drop columns by name in a data frame
I have a large data set and I would like to read specific columns or drop all the others.
11 Answers
...
Using emit vs calling a signal as if it's a regular function in Qt
...e this:
#ifndef QT_NO_EMIT
# define emit
#endif
(The define guard is to allow you to use Qt with other frameworks that have colliding names via the no_keywords QMake config option.)
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