C language can be used to write crawler programs, but compared to other programming languages, crawler development in C language may be more complicated and cumbersome. Because the C language itself does not provide a ready-made crawler framework and library, you need to write your own functions such as network requests and HTML parsing.
However, if you are familiar with C language, you can also try to write a crawler program in C language, so that you can better grasp the underlying principles and implementation methods of crawlers. When writing C language crawlers, you can use some third-party libraries to simplify development, such as libcurl for network requests, libxml2 for HTML parsing, etc.
Why are C language crawlers unpopular?
The C language is not as suitable for writing crawlers as languages such as Python and Java, mainly because of the following reasons:
1. The C language supports relatively weak strings and dynamic memory management. When parsing HTML, you need to deal with a large number of strings and memory allocation issues, which requires using additional libraries or implementing related functions by yourself, which will increase the difficulty and workload of development.
2. The C language itself is not suitable for IO-intensive operations, such as network transmission. In many crawler scenarios, it is necessary to download web pages or other data through ∨∨∨, or exchange or request data through network APIs. Although the C language supports low-level network programming such as sockets, it will be more cumbersome and complicated than using a high-level language.
3. There are currently many popular high-level languages (such as Python, Java, etc.) that can be easily implemented as crawlers. Compared with these languages, C language has fewer documents and information and an imperfect ecological environment, and is inferior to modern high-level programming languages in terms of development efficiency and code reusability.
4. For most crawler tasks, the performance advantage of C language is not as obvious as before. After introducing many concurrent libraries and asynchronous processing methods, the performance of the already fast Python code is comparable to that of C language. .
To sum up, due to the native features of C language and its disadvantages in crawler development, many developers often choose other programming languages and more suitable tools to complete crawler development tasks.
The C language is not as suitable for writing crawlers as languages such as Python and Java, but there are some libraries and tools available, such as:
libCURL: is a free, open source, reusable, easy-to-use client-side URL transfer library that can be used to get data from a given URL and parse HTML content, supporting protocols such as HTTPS, HTTP, FTP, and Telnet.
Gumbo: It is a C language HTML5 parser library developed by Google, similar to Python's Beautiful Soup, but it is only responsible for parsing and manipulating HTML fragments, and does not involve network transmission and data request related issues.
WebkitGTK+: It is a browser engine library for Linux systems, providing a C language interface, which is very suitable for use in GTK+-based applications, and can directly load and render HTML pages.
The following is the sample code of the libCURL library used by Huake Cloud Business technicians:
#include <stdio.h>
#include <curl/curl.h>
int main(void)
{
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "∧∧∧∧∧∧∧∧∧∧∧∧∧∧∧∧∧");
res = curl_easy_perform(curl);
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
curl_easy_cleanup(curl);
}
0;
}
The above code uses the curl_easy_init() function to initialize the libCURL library, then sets the URL that needs to fetch data, and calls the curl_easy_perform() function to perform the fetch operation. In actual development, more network requests and HTML parsing issues need to be considered.
In general, although the C language is not the best choice to write crawlers, in some fields such as the development of embedded systems and high-performance computing applications, it is necessary to directly operate the underlying network protocols and data transmission. At this time, it may be used C language to realize the crawler function.