Golang Web Scraper Example

Let's clear some things. A Selection is a collection of nodes matching some criteria. Doc.Find is Selection.Find which returns a new Selection containing the elements matching the criteria. And Selection.Each iterations over each of the elements of the collection and calls the function value passed to it. So in your case Find('tbody') will find all tbody elements, Each will iterate. Colly provides a clean interface to write any kind of crawler/scraper/spider. With Colly you can easily extract structured data from websites, which can be used for a wide range of applications, like data mining, data processing or archiving. By Divyanshu Shekhar. In Golang, Go Web Development. On June 20, 2020. A Simple HTTP Server in Golang can easily be created using Golang’s net/http package. In this blog, we will be creating a simple HTTP Server in Golang that will render some text on the browser. Web scrapping with Golang Web scrapping with Golang. September 4, 2018 kavi Comments 0 Comment. Web scrapping is a technic to parse HTML output of website. Most of the online bots are based on same technic to get required information about particular website or page. Web Scraper code to get post from website.

Golang Web Scraper Example

Web scrapping is a technic to parse HTML output of website. Most of the online bots are based on same technic to get required information about particular website or page.

A week ago I decided to try my hand at web scraping. The initial plan was to use python, but when looking up on YouTube I happened to come across this video on web scraping using Golang and Colly. Given my level of comfort using Golang being better than using Python, I decided to go ahead with Golang.

Using XML parser we can parse HTML page and get the required information. However, jquery selector are best to parse HTML page. So, in this tutorial we will be using Jquery library in Golang to parse the HTML doc.

Project Setup and dependencies

As mention above, we will be using Jquery library as a parser. So go get the library using following command

Golang Web Scraper Example

Create a file webscraper.go and open it in any of your favorite text editor.

Web Scraper code to get post from website

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I stumbled across a scraper and crawler framework written in Go called Colly. Colly makes it really easy to scrape content from web pages with it’s fast speed and easy interface. I have always been interested in web scrapers ever since I did a project for my university studies and you can read about that project here. Before continuing, please note that scraping of websites is not always allowed and sometimes even illegal. In the guide below we will be parsing this blog, GoPHP.io.

To begin let’s take a look at the Colly Github page and scroll down to the example code listed there. We will create a new project with a new main.go file that looks like this:

Golang Web Scraper Example

You may need to use go get -u github.com/gocolly/colly/... to download the framework into your go directory. Now let’s go ahead and change the url to the gophp.io website.

And then we can run the script by typing go run main.go in your terminal making sure you are in the project directory when you do this. You can use ctrl+c in your terminal to cancel as it may run for a long time. What do we get as our output? For me it looked like this:

What we see here is exactly what you would expect. Our program parsed all the urls on the main gophp.io page and then proceeded to the first link. This first link is a post at gophp.io but the first link on that page is a link to Virtualbox and our program will keep looping until it stops finding links. That could be a long time and unless you want to make a search engine spider it won’t be the most efficent. What I want is a server that I can call on from a PHP script that just fetches and formats the data I need. Luckily Colly has a complete example of what we need, a scraper server.

What does the above code do? It will start a webserver running locally on your machine on port 7171. It takes a url parameter and returns all the links found on the url you input. Let’s give it a go by going to http://127.0.0.1:7171/?url=https://gophp.io/. Here is an example of the json encoded output we get:

Golang Web Scraper Examples

The above json output is only 1 level deep. Notice that it does not keep finding links on the pages it finds. This is great because now we could use this program as a sort of microservice. A PHP application could make calls to this microservice and receive all links for the specified url which could later be processed by the PHP application. Now, links are good but we might want to parse other content on the page. Let’s customize our code for this purpose.

Queries For Specific Content With Colly

If we take a look at the source of gophp.io we can see that every title has the css class entry-title which we can use for our query. We will modify the handler function by adding another map for headings. I am only including the section of code that I have changed below:

Now if we restart our program and navigate to our page on port 7171 again we will see some additional output in our json response.

As you can see we have now parsed all the titles on the page and added them to our json output. Using queries we can make very general or specific parsers for any kind of website.

Golang Web Service Example

I hope this guide helps someone get started with web scraping. There are several real world examples in the documentation if you would like to learn more. I would love to hear your feedback, questions and comments below!