C++ 23 cheatsheet

C++ 23: Input, exceptions and threads

7 common C++ 23 tasks.

Read a file line by line

Read a text file with ifstream and getline.

std::ifstream file("data.txt");
std::string line;
while (std::getline(file, line)) {
    std::cout << line << '\n';
}

Read a line from the keyboard

Read a whole line, including spaces.

std::string name;
std::getline(std::cin, name);

Handle exceptions

Catch exceptions by const reference.

try {
    auto n = std::stoi(text);
} catch (const std::exception& e) {
    std::cerr << e.what() << '\n';
}

Run code on another thread

Start a thread and wait for it. std::jthread joins automatically when it is destroyed (C++20).

std::jthread worker([] { std::cout << "working\n"; });

Compute a value in the background

Run a function asynchronously and collect the result later.

auto fut = std::async(std::launch::async, [] { return 6 * 7; });
std::cout << fut.get() << '\n';

Share a counter between threads

An atomic integer can be updated by several threads without a mutex.

std::atomic<int> hits{0};
++hits;

Time a section of code

Measure elapsed time with a steady clock.

auto start = std::chrono::steady_clock::now();
work();
auto ms = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::steady_clock::now() - start).count();