libcurl for C++: Complete Guide with Examples

What is libcurl and why is it needed

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libcurl is a powerful and widely used cross-platform library for data transfer over various network protocols. Written in C, it provides a C++ interface (often called curlpp or simply a libcurl wrapper) for making HTTP requests, downloading files, working with FTP, SMTP, and many other protocols. In the context of C++, libcurl is the de facto standard for creating HTTP clients.

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Why is libcurl needed in C++?

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• Working with REST API: Sending GET, POST, PUT, DELETE requests to web services.
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• Downloading files: Downloading images, documents, archives from the internet.
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• Sending data: Uploading files to a server, submitting forms.
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• Web scraping: Retrieving HTML code for further analysis.
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• Authentication: Support for Basic, Digest, OAuth, NTLM, and other schemes.
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• Working with cookies: Managing sessions and state.
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• SSL/TLS: Secure connection via HTTPS.
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The library is known for its high performance, stability, and support for virtually all modern network protocols. It is used in projects such as cURL (command line), PHP (cURL extension), and many others.

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Installing libcurl for C++

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Unlike Python or JavaScript, C++ does not have a single package manager, so installation depends on your operating system and compiler.

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Installation on Linux (Ubuntu/Debian)

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sudo apt update\nsudo apt install libcurl4-openssl-dev

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For other distributions (Fedora, CentOS, Arch), use the corresponding package managers (dnf, yum, pacman).

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Installation on macOS

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brew install curl

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Installation on Windows

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The easiest way is to use vcpkg:

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git clone https://github.com/Microsoft/vcpkg.git\ncd vcpkg\n.\\bootstrap-vcpkg.bat\n.\\vcpkg integrate install\n.\\vcpkg install curl

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Or download pre-built binaries from the official curl website.

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Connecting in a CMake project

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find_package(CURL REQUIRED)\ntarget_link_libraries(your_project PRIVATE CURL::libcurl)

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Quick start: simple HTTP GET request

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Let's write a simple program that performs a GET request to a website and outputs the received data.

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#include <iostream>\n#include <string>\n#include <curl/curl.h>\n\n// Callback function for writing data to a string\nsize_t WriteCallback(void* contents, size_t size, size_t nmemb, std::string* output) {\n    size_t totalSize = size * nmemb;\n    output->append(static_cast<char*>(contents), totalSize);\n    return totalSize;\n}\n\nint main() {\n    CURL* curl;\n    CURLcode res;\n    std::string response;\n\n    curl_global_init(CURL_GLOBAL_DEFAULT);\n    curl = curl_easy_init();\n\n    if (curl) {\n        curl_easy_setopt(curl, CURLOPT_URL, "https://api.github.com");\n        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);\n        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);\n        \n        // Perform the request\n        res = curl_easy_perform(curl);\n        \n        if (res != CURLE_OK) {\n            std::cerr << "Error: " << curl_easy_strerror(res) << std::endl;\n        } else {\n            std::cout << "Server response:" << std::endl;\n            std::cout << response << std::endl;\n        }\n        \n        curl_easy_cleanup(curl);\n    }\n\n    curl_global_cleanup();\n    return 0;\n}

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Compilation:

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g++ -o http_client http_cl