MongoDB: How to update multiple documents with a single command?

Multi update was added recently, so is only available in the development releases (1.1.3). From the shell you do a multi update by passing true as the fourth argument to update(), where the the third argument is the upsert argument:

db.test.update({foo: "bar"}, {$set: {test: "success!"}}, false, true);

For versions of mongodb 2.2+ you need to set option multi true to update multiple documents at once.

db.test.update({foo: "bar"}, {$set: {test: "success!"}}, {multi: true})

For versions of mongodb 3.2+ you can also use new method updateMany() to update multiple documents at once, without the need of separate multi option.

db.test.updateMany({foo: "bar"}, {$set: {test: "success!"}})

Starting in v3.3 You can use updateMany

db.collection.updateMany(   <filter>,   <update>,   {     upsert: <boolean>,     writeConcern: <document>,     collation: <document>,     arrayFilters: [ <filterdocument1>, ... ]   })

In v2.2, the update function takes the following form:

 db.collection.update(   <query>,   <update>,   { upsert: <boolean>, multi: <boolean> })

https://docs.mongodb.com/manual/reference/method/db.collection.update/

For Mongo version > 2.2, add a field multi and set it to true

db.Collection.update({query},                  {$set: {field1: "f1", field2: "f2"}},                 {multi: true })