Making Mongodb Shell scripts, getting started.

In this post on mongodb, I will be writing about making mongodb shell scripts. These are scripts that can be called from the mongodb shell with the load command, or directly from the main os command line interface my calling mongodb and then passing the path of the js file. These scripts can be used to work with any of the database methods in the mongo shell such as db.getName.

1 - what to know

This is a post on mongodb shell scripts. It is not a getting stared post on mongodb, javaScript, node.js or any other topics that you should know at least a thing or two about before hand in order to get anything of value from these posts.

2 - writing a hello world mongodb shell script

Start by making a folder that will be used to store the shell scripts. If these scripts will be closely tied to a particular project then I might want to call the folder something like mongo_shell or something to that effect in the root path of a project folder.

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$ mkdir mongo_shell
$ cd mongo_shell

After making a new folder to store shell scripts in I then create a file called helloworld.js that looks like this:

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printjson("hello World");

2.1 - running the helloworld.js mongodb shell script from the command line

When that is done I can then call the script from the command line, assuming that the current working directory is the same as where the script is located, this will call the script.

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$ mongo helloworld.js
MongoDB shell version v4.0.0
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 4.0.0
"hello World"

2.2 running the helloworld.js mongodb shell script from the mongo shell using the load command.

Although most of the time I would want to just run the script from the command line directly, when working withing the mongodb shell scripts can be called from within these using the load command.

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$ mongo
MongoDB shell version v4.0.0
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 4.0.0
---
> load('helloworld.js')
"hello World"
true
> exit
bye

3 - An example the prints some info about a database

So a script can be used to do anything that would be done manually in the mongoShell. Including using methods that get the name of the current database that is being used, and a list of the collection names.

So I could make a script called connect_users.js that connects to and displays some information about a database called ‘mongoose_users’.

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conn = new Mongo();
db = conn.getDB('mongoose_users');
printjson({"dbName":db.getName(), "collectionNames": db.getCollectionNames()});

Works like a charm

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$ mongo connect_users.js
MongoDB shell version v4.0.0
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 4.0.0
{ "dbName" : "mongoose_users", "collectionNames" : [ "users" ] }

4 - conclusion

So this was just a quick getting stared post on theses kinds of scripts. I might write more posts on this in the future as my content on mongodb continues to grow.