What are the limitations of using Curl for web scraping?

Curl is a powerful tool that is used for transferring data to or from a server and it supports a wide range of protocols. It is often used for web scraping, the practice of automating the extraction of data from websites. However, there are some limitations when using Curl for web scraping.

1. Difficulty Handling JavaScript: Curl doesn't interpret JavaScript. Most modern websites use JavaScript to load or display content, meaning that Curl might not be able to see everything that a normal web browser can see.

2. Session Handling: Curl does not handle sessions in the same way as a web browser. This means that it can be more difficult to manage cookies and maintain state between requests.

3. Difficulty Scraping Complex Websites: It can be harder to scrape more complex websites that require interaction or have a complicated structure, as Curl isn't built for web navigation.

4. Lack of built-in parsing: Curl does not inherently support HTML parsing. This makes it more difficult to extract specific elements from the HTML document.

5. Time-Consuming: For large scraping tasks, Curl can be slower and more time-consuming compared to other tools.

Though Curl has these limitations, it can still be used for web scraping in conjunction with other tools. For example, you can use Curl to fetch a webpage's content and then use a parsing library such as BeautifulSoup in Python or Cheerio in JavaScript to parse the HTML.

Below is a simple example of using Curl and BeautifulSoup in Python:

import os
from bs4 import BeautifulSoup

# Use Curl to fetch a webpage's content
os.system("curl https://example.com > temp.html")

# Open the file with BeautifulSoup
with open("temp.html") as fp:
    soup = BeautifulSoup(fp, 'html.parser')

# Extract data
data = soup.find_all('div', {'class': 'example'})

# Remember to remove the temporary file
os.remove("temp.html")

And here is an example of using Curl and Cheerio in JavaScript:

const exec = require('child_process').exec;
const cheerio = require('cheerio');

// Use Curl to fetch a webpage's content
exec("curl https://example.com", (error, stdout, stderr) => {
    if (error) {
        console.error(`exec error: ${error}`);
        return;
    }

    // Load the HTML into Cheerio
    const $ = cheerio.load(stdout);

    // Extract data
    const data = $('.example').map((i, element) => {
        return $(element).text();
    }).get();
});

Remember that web scraping should always be done in accordance with the website's terms of service and with respect for the server's resources.