Mongodb-the MONGO Shell, Access the MONGO shell help

In addition to the documentation in the MongoDB Manual, the MONGO Shell provides some additional information in I TS "Online" Help system. This document provides a overview of accessing this Help information.

Command line Help

The list of options and help for starting the MONGO shell with the --help option from the command Line

MONGO--help

Shell Help

To see the list of help, in the MONGO shell, type help:

Help

Database Help

In the MONGO Shell:

• To the list of databases in the server, use the show dbs command:

  Show DBS

  New in version 2.4: Show Databases is now a alias for show DBS

• To see the list of Help for methods you can use on the DB object, call the db.help () method:

  Db.help ()

• To see the implementation of a method in the shell, type the db.<method name> without the parenthesis ( ()), as in the following example which would return the implementation of the method Db.updateuser ():

  Db.updateuser

Collection Help

In the MONGO Shell:

• The list of collections in the current database, use the show Collections command:

  Show collections

• To see the methods available on the collection objects (e.g. db.<collection>) , use the db.< Collection>.help () method:

  Db.collection.help ()

  <collection> Can is the name of a collection that exists, although specify a collection that doesn ' T exist.

• To see the collection method implementation, type the db.<collection>.<method> name without the Paren Thesis (()), as in the following example which would return the implementation of the Save ()method:

  Db.collection.save

Cursor Help

When you perform read Operations with the  find ()  method in the &NBSP;mongo  shell , you can use various cursor methods to modify THE&NBSP;find ()  behavior and various JavaScript methods to handle the cursor returned from the < TT class= "XRef mongodb mongodb-method docutils literal" >find ()  method.

• To list the available modifier and cursor handling methods with the Db.collection.find (). Help () command:

  Db.collection.find (). Help ()

  <collection> Can is the name of a collection that exists, although specify a collection that doesn ' T exist.

• To see the implementation of the cursor method, type the db.<collection>.find () .<method> name without  The parenthesis (()), as in the following example which would return the implementation of the ToArray () Method

  Db.collection.find (). ToArray

Some useful methods for handling cursors is:

• Hasnext () which checks whether the cursor has a more documents to return.
• next () which returns the next document and advances the cursor position forward by one.
• ForEach (<function>) which iterates the whole cursor and applies the <function> to each docum ENT returned by the cursor. The <function> expects a single argument which corresponds to the document from each iteration.

For examples on iterating a cursor and retrieving the "documents from the" cursor, see cursor handling. See also cursor for all available cursor methods.

Wrapper Object Help

To get a list of the wrapper classes available in the MONGO shell, such as Bindata (), type help misc in the MONGO Shell:

Help Misc

Mongodb-the MONGO Shell, Access the MONGO shell help