The mongo
Shell¶
On this page
Introduction¶
The mongo
shell is an interactive JavaScript interface to
MongoDB. You can use the mongo
shell to query and update
data as well as perform administrative operations.
The mongo
shell is included as part of the MongoDB Server installation. MongoDB also provides the mongo
shell as a standalone package. To download the standalone mongo
shell package:
Open the Download Center. For the
mongo
Enterprise Shell, select the MongoDB Enterprise Server tab.Select your preferred Version and OS from the dropdowns.
Select
Shell
from the Package dropdown and click Download to start downloading the package.If the
Shell
option is unavailable for the selected OS and Version, contact MongoDB Technical Support for assistance.
Once you have installed and have started MongoDB, connect
the mongo
shell to your running MongoDB instance.
Note
Starting in MongoDB 3.6.15, the mongo
shell displays a
warning message when connected to non-genuine MongoDB instances as
these instances may behave differently from the official MongoDB
instances; e.g. missing or incomplete features, different feature
behaviors, etc.
Most examples in the MongoDB Manual use the
mongo
shell; however, many drivers provide similar interfaces to MongoDB.
Start the mongo
Shell¶
Important
Ensure that MongoDB is running before attempting to start the
mongo
shell.
To start the mongo
shell and connect to your MongoDB instance running on localhost with
default port:
At a prompt in a terminal window (or a command prompt for Windows), go to your
<mongodb installation dir>
:Type
./bin/mongo
to startmongo
:If you have added the
<mongodb installation dir>/bin
to thePATH
environment variable, you can just typemongo
instead of./bin/mongo
.
Options¶
When you run mongo
without any arguments, the
mongo
shell will attempt to connect to the MongoDB instance
running on the localhost
interface on port 27017
. To specify a
different host or port number, as well as other options, see
examples of starting up mongo and
mongo reference which provides
details on the available options.
.mongorc.js
File¶
When starting, mongo
checks the user’s HOME
directory for a JavaScript file named .mongorc.js. If found, mongo
interprets the
content of .mongorc.js
before displaying the prompt for the
first time. If you use the shell to evaluate a JavaScript file or
expression, either by using the --eval
option on the command line or by specifying a .js file to
mongo, mongo
will read the
.mongorc.js
file after the JavaScript has finished processing.
You can prevent .mongorc.js
from being loaded by using the
--norc
option.
Working with the mongo
Shell¶
To display the database you are using, type db
:
The operation should return test
, which is the default database.
To switch databases, issue the use <db>
helper, as in the
following example:
To list the available databases, use the helper show dbs
. See also
db.getSiblingDB()
method to access a different database from
the current database without switching your current database context
(i.e. db
).
You can switch to non-existing databases. When you first store data in
the database, such as by creating a collection, MongoDB creates the
database. For example, the following creates both the database
myNewDatabase
and the collection myCollection
during
the insertOne()
operation:
The db.myCollection.insertOne()
is one
of the methods available in the mongo shell.
db
refers to the current database.myCollection
is the name of the collection.
If the mongo
shell does not accept the name of a collection,
you can use the alternative db.getCollection()
syntax.
For instance, if a collection name contains a space or hyphen, starts
with a number, or conflicts with a built-in function:
The mongo
shell prompt has a limit of 4095 codepoints for
each line. If you enter a line with more than 4095 codepoints, the
shell will truncate it.
For more documentation of basic MongoDB operations in the
mongo
shell, see:
- Getting Started Guide for the mongo Shell
- Insert Documents
- Query Documents
- Update Documents
- Delete Documents
- mongo Shell Methods
Format Printed Results¶
The db.collection.find()
method returns a cursor to
the results; however, in the mongo
shell, if the returned
cursor is not assigned to a variable using the var
keyword, then
the cursor is automatically iterated up to 20 times to print up to the
first 20 documents that match the query. The mongo
shell
will prompt Type it
to iterate another 20 times.
To format the printed result, you can add the .pretty()
to the
operation, as in the following:
In addition, you can use the following explicit print methods in the
mongo
shell:
print()
to print without formattingprint(tojson(<obj>))
to print with JSON formatting and equivalent toprintjson()
printjson()
to print with JSON formatting and equivalent toprint(tojson(<obj>))
For more information and examples on cursor handling in the
mongo
shell, see Iterate a Cursor in the mongo Shell. See also
Cursor Help for list of cursor help in the
mongo
shell.
Multi-line Operations in the mongo
Shell¶
If you end a line with an open parenthesis ('('
), an open brace
('{'
), or an open bracket ('['
), then the subsequent lines start
with ellipsis ("..."
) until you enter the corresponding closing
parenthesis (')'
), the closing brace ('}'
) or the closing
bracket (']'
). The mongo
shell waits for the closing
parenthesis, closing brace, or the closing bracket before evaluating
the code, as in the following example:
You can exit the line continuation mode if you enter two blank lines, as in the following example:
Tab Completion and Other Keyboard Shortcuts¶
The mongo
shell supports keyboard shortcuts. For example,
Use the up/down arrow keys to scroll through command history. See .dbshell documentation for more information on the
.dbshell
file.Use
<Tab>
to autocomplete or to list the completion possibilities, as in the following example which uses<Tab>
to complete the method name starting with the letter'c'
:Because there are many collection methods starting with the letter
'c'
, the<Tab>
will list the various methods that start with'c'
.
For a full list of the shortcuts, see Shell Keyboard Shortcuts
Exit the Shell¶
To exit the shell, type quit()
or use the <Ctrl-C>
shortcut.
See also
- Getting Started Guide for the mongo Shell
mongo
Reference Page