Sending Files in Sinatra

Introduction 

Sinatra is an open-source web application framework of Ruby. It is an alternative to Ruby on Rails among the other web application frameworks based on Ruby. It is more robust and hence requires more work and time for development.

This article will discuss how to send files in Sinatra. We will illustrate the concept with the help of an example.

Sending Files in Sinatra

If you wish to get the contents of a file as a response, you can use the send_file helper method in Sinatra. A helper method is a pre-defined method that helps perform a specific task. It has the instructions written already, and we have to invoke the function without understanding the underlying details of how it is executing.  

Example 1

Create a demo.rb file as follows: 

require 'sinatra'
get '/' do
  send_file 'Coding_Ninjas_Logo.png'
end

You can also try this code with Online Ruby Compiler

Run Code

Output 

Run ruby demo.rb on the command line after making sure you are in the same directory as where the demo.rb file is saved. You will see the following results.
 

Now visit http://localhost:4567, and you will see the below page.
 

Optional Parameters of send_file method

You can pass several parameters or options to the send file method. All of these parameters are optional. 

:filename

You can specify the file name you want to use in the response using this parameter. By default, the filename is the same as the original file’s name.

:type

This parameter is used to set the value of the Content-Type header. By default, the type value is guessed by the file extension. You can also specify the type. 

:last_modified

The last_modified parameter is used to set the value of the Last-Modified header. By default, it is the same as the file's mtime.

:length

It sets the value of the Content-Length header. By default, it is the same as the size of the file sent. 

:disposition

It specifies the value of the Content-Disposition header. The possible values for d :disposition parameters are: nil, :attachment, and :inline. By default, it is set to nil. 

:status

Using this option, you can specify the status code you want to send with the file. It can be used to send a static file as an error page. 

Example 2

In this example, we will be sending an error image. First, we create an Error image we want to send, then using the helper method send_file, we send the image to the response. 

Create an error_file.rb as shown below:

require 'sinatra'

get '/' do
  send_file 'error_image.png'
end

You can also try this code with Online Ruby Compiler

Run Code

Output

Visit http://localhost:4567, and you will see the below page.