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By David Li on Fri, 7 July 2024

Web scraping is the process of extracting data from websites. It is a powerful tool for data scientists and analysts who need to collect data from various sources. In this article, we will walk through the process of building a web scraper in Rust using popular libraries like reqwest, select, and scraper.

Before we get started, it is important to note that web scraping can be a contentious issue. Some website owners may view web scraping as a violation of their terms of service or even as an illegal activity. As such, it is important to ensure that you are not violating any laws or terms of service when building your web scraper.

Step 1: Setup

The first step in building a web scraper in Rust is to set up a new Rust project. You can use your favorite IDE or text editor to create a new Rust project. For this tutorial, we will be using the cargo command to create a new project:

cargo new my_scraper
cd my_scraper

Step 2: Dependencies

The next step is to add the necessary dependencies to our project. We will be using the reqwest, select, and scraper libraries for this. Add the following lines to your Cargo.toml file:

[dependencies]
reqwest = "0.11.4"
select = "0.6.0"
scraper = "0.13.0"

The reqwest library is used for making HTTP requests to websites. The select library is used for parsing HTML documents and selecting specific elements from them. The scraper library is built on top of select and provides a more convenient interface for parsing HTML documents.

Step 3: Making HTTP requests

Now that we have our dependencies set up, we can start making HTTP requests to websites. In this example, we will be scraping data from the Hacker News website.

use reqwest::Error;
use scraper::{Html, Selector};

#[tokio::main]
async fn main() -> Result<(), Error> {
    let url = "https://news.ycombinator.com/";
    let body = reqwest::get(url).await?.text().await?;

    let document = Html::parse_document(&body);
    let selector = Selector::parse(".storylink").unwrap();

    for element in document.select(&selector) {
        let link = element.value().attr("href").unwrap_or("");
        let title = element.text().collect::<Vec<_>>().join("");
        println!("{} ({})", title, link);
    }

    Ok(())
}

We start by defining the URL of the website we want to scrape. We then use the reqwest library to make an HTTP request to the website and get the HTML body of the response. We use the Html::parse_document function from the scraper library to parse the HTML document and create a Document object.

We then use the Selector::parse function from the select library to select all elements with the class storylink. We loop through each of these elements and extract the link and title information using the attr and text methods provided by the scraper library.

Step 4: Saving data

Once we have scraped the data we need, we can save it to a file or database for further processing. In this example, we will simply print the data to the console.

use std::fs::File;
use std::io::prelude::*;

#[tokio::main]
async fn main() -> Result<(), Error> {
    let url = "https://news.ycombinator.com/";
    let body = reqwest::get(url).await?.text().await?;

    let document = Html::parse_document(&body);
    let selector = Selector::parse(".storylink").unwrap();

    let mut file = File::create("output.txt").unwrap();

    for element in document.select(&selector) {
        let link = element.value().attr("href").unwrap_or("");
        let title = element.text().collect::<Vec<_>>().join("");
        let line = format!("{} ({})\n", title, link);
        file.write_all(line.as_bytes()).unwrap();
    }

    Ok(())
}

In this example, we create a new file called output.txt and write each scraped line to the file using the write_all method provided by the std::io::prelude module.

Conclusion

In this article, we have walked through the process of building a web scraper in Rust using popular libraries like reqwest, select, and scraper. We have shown how to make HTTP requests to websites, parse HTML documents, and save the scraped data to a file. With this knowledge, you can build powerful web scraping tools to collect and analyze data from the web.

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