mongoDB Logo - mongo shell scriptingLearn how to create a JavaScript file that executes mongo shell commands

Why Mongo Shell Scripting ?

In the article: “Getting Started With the Mongo Shell – Basic CRUD Operations“, I covered the basics needed to perform CRUD operations on a MongoDB database, using the mongo shell. All of the examples in that article were in real-time. This is perfectly acceptable, and there may be cases in which you will want to perform administrative tasks manually. But it is also possible (and more likely) that you’ll want to create a script that executes a batch of mongo shell tasks. So, since JavaScript is the language used to interact with the mongo shell, we can pass a JS file to the mongo command in a terminal. This is mongo shell scripting.

This functionality offers a great deal of potential. For example, in this article I will provide a very simple demonstration that performs basic CRUD operations (“Create, Read, Update, Delete”).

An important note about the following examples:

If you want to run these examples locally, you have two options:

  1. Clone this GitHub repo and follow the instructions: https://github.com/kevinchisholm/mongo-shell-scripting-basic-crud-operations 
  2. Scroll down to the section: “How to Demo“, and then follow the instructions

Creating a Database

Create the “madMen” database – Example # 1

In Example # 1, we create the “madMen” database and establish a connection to it. The “allMadMen” variable is set to null for now, but will indeed be used in the next example.

Adding Data to / Reading Data from a Database

Create the “names” collection – Example # 2

In Example # 2, we create the “names” collection and then add four documents to it. We then use the “allMadMen” variable to store a reference to the names collection, and then iterate it. The purpose of the iteration is to allow you to see in your terminal that the madMen database has actually been populated with documents. Example # 2 demonstrates both the “Create” part of our CRUD operations, and  the “Read” part as well.

Updating A Collection Document

Let’s make a change to “Donald Draper” – Example # 3

Example # 3 is the “U” in our CRUD operation; in other words: “Update”. Here we use the forEach method of the names collection to iterate and find the document whose “name” property is set to: “Don Draper”. So, once we find that document, we update its “name” property to: “Dick Whitman”.

Deleting A Collection Document

Let’s delete “Dick Whitman.” – Example # 4

In Example # 4, we delete the document whose “name” property is set to: “Dick Whitman.

Dropping a Database

Drop the “madMen” database – Example # 5

db.dropDatabase();

In Example # 5, we drop the “madMen” database.

The Entire App – Example # 6A

In Example # 6A, we have the completed example code. To demonstrate, numerous print and printjson statements have been added so that the terminal output makes a bit more sense.

The Output – Example # 6B

In Example # 6B, we have the terminal output from the code in Example # 6A.

How to Demo:

  • Make sure the MongoDB database server is running
  • Create a file named: “create-db.js”.
  • Copy the entire contents of Example # 6 to “create-db.js
  • In a terminal window, execute the following command: “mongo create-db.js

Summary

In summary, we learned how to perform basic CRUD operations on a MongoDB database by leveraging mongo shell scripting.

Helpful Links for Mongo Shell Scripting

Getting Started With the Mongo Shell – Basic CRUD Operations | Kevin Chisholm – Blog

http://docs.mongodb.org/manual/administration/scripting/

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