How to return number of updated objects in mongodb?

Question

I'm updating multiple elements in mongodb. Is it possible to return the number of affected objects?

Answer 1

Use getLastError. The n key will contain the number of updated documents

> db.count.update({x : 1}, {$inc : {x : 1}}, false, true)
> db.runCommand({getLastError : 1})
{
"err" : null,
"updatedExisting" : true,
"n" : 5,
"ok" : true
}

Note that this runs the command "getLastError" which returns the number of rows after the update command has completed.

Database commands are listed here.