大约有 48,000 项符合查询结果（耗时：0.0731秒） [XML]
What is the difference between ${var}, “$var”, and “${var}” in the Bash shell?
...
Braces ($var vs. ${var})
In most cases, $var and ${var} are the same:
var=foo
echo $var
# foo
echo ${var}
# foo
The braces are only needed to resolve ambiguity in expressions:
var=foo
echo $varbar
# Prints nothing because there is no variable 'varbar'
echo ${var}bar...
PDO closing connection
...ber of other reasons. When connecting or running a query, catch any error, and if it is "MySQL has gone away", attempt to connect again or run the query a second time.
– Frank Forte
Dec 14 '17 at 20:50
...
How do I perform the SQL Join equivalent in MongoDB?
...t array field>
}
}
Of course Mongo is not a relational database, and the devs are being careful to recommend specific use cases for $lookup, but at least as of 3.2 doing join is now possible with MongoDB.
share
...
how to override left:0 using CSS or Jquery?
...
The default value for left is auto, so just set it to that and you will "reset" it.
.elem {
left: auto;
}
Make sure that the above comes after the original CSS file.
share
|
imp...
Scheduling recurring task in Android
...ng. This guarantees that the phone will not sleep until you have finished handling the broadcast. Once onReceive() returns, the Alarm Manager releases this wake lock. This means that the phone will in some cases sleep as soon as your onReceive() method completes. If your alarm receiver called Contex...
Should I use the Reply-To header when sending emails as a service to others?
...
You may want to consider placing the customer's name in the From header and your address in the Sender header:
From: Company A <joe.bloggs@a.com>
Sender: notifications@b.com
Most mailers will render this as "From notifications@b.com on behalf of Company A", which is accurate. And then a...
Why catch and rethrow an exception in C#?
...about where the exception actually was created.
Second, if you just catch and re-throw like that, I see no added value, the code example above would be just as good (or, given the throw ex bit, even better) without the try-catch.
However, there are cases where you might want to catch and rethrow a...
Git - working on wrong branch - how to copy changes to existing topic branch
...orking on a project, but unfortunately, I forgot to switch to my branch, and as such have been working on master
4 Answer...
Saving a Numpy array as an image
...yPNG. It's a pure Python (no dependencies) open source PNG encoder/decoder and it supports writing NumPy arrays as images.
share
|
improve this answer
|
follow
...
Is it unnecessary to put super() in constructor?
... or protected or, if both classes are in the same package, package access; and
Default constructor: the public no-args constructor added by the compiler when there is no explicit constructor in the class.
So all classes have at least one constructor.
Subclasses constructors may specify as the fir...