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mongo group query how to keep fields
...h group, you can try aggregating like:
db.test.aggregate({
$group: {
_id : '$name',
name : { $first: '$name' },
age : { $first: '$age' },
sex : { $first: '$sex' },
province : { $first: '$province' },
city : { $first: '$city' },
area : { $first: '$area' },
address : { $firs...
/usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.15' not found
How can I get GLIBCXX_3.4.15 in Ubuntu? I can't run some programs that I'm compiling.
19 Answers
...
Linq to Sql: Multiple left outer joins
...SQL:
Dim db As New ContractDataContext()
Dim query = From o In db.Orders _
Group Join v In db.Vendors _
On v.VendorNumber Equals o.VendorNumber _
Into ov = Group _
From x In ov.DefaultIfEmpty() _
Group Join s In db.Status _
On...
URL rewriting with PHP
...
You can essentially do this 2 ways:
The .htaccess route with mod_rewrite
Add a file called .htaccess in your root folder, and add something like this:
RewriteEngine on
RewriteRule ^/?Some-text-goes-here/([0-9]+)$ /picture.php?id=$1
This will tell Apache to enable mod_rewrite for this ...
How to obtain the number of CPUs/cores in Linux from the command line?
...
The most portable solution I have found is the getconf command:
getconf _NPROCESSORS_ONLN
This works on both Linux and Mac OS X. Another benefit of this over some of the other approaches is that getconf has been around for a long time. Some of the older Linux machines I have to do development o...
Instagram how to get my user id from username?
...request is made with the url below:
https://www.instagram.com/{username}/?__a=1
E.g:
This url will get all information about a user whose username is therock
https://www.instagram.com/therock/?__a=1
Update i June-20-2019, the API is public now. No authentication required.
Update in Decembe...
How to set child process' environment variable in Makefile
...ever you can use make's export to force them to do so. Change:
test: NODE_ENV = test
to this:
test: export NODE_ENV = test
(assuming you have a sufficiently modern version of GNU make >= 3.77 ).
share
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...
Create a menu Bar in WPF?
...nel>
<Menu DockPanel.Dock="Top">
<MenuItem Header="_File">
<MenuItem Header="_Open"/>
<MenuItem Header="_Close"/>
<MenuItem Header="_Save"/>
</MenuItem>
</Menu>
<StackPanel></StackPa...
Detecting endianness programmatically in a C++ program
...e warned against by compiler. That's exactly what unions are for !
bool is_big_endian(void)
{
union {
uint32_t i;
char c[4];
} bint = {0x01020304};
return bint.c[0] == 1;
}
The principle is equivalent to the type case as suggested by others, but this is clearer - and...
Run a callback only if an attribute has changed in Rails
...
Rails 5.1+
class Page < ActiveRecord::Base
before_save :do_something, if: :will_save_change_to_status_id?
private
def do_something
# ...
end
end
The commit that changed ActiveRecord::Dirty is here: https://github.com/rails/rails/commit/16ae3db5a5c6a08383b974ae...