C++:
Logging

How to:

Let’s say you’re working on a Linux box and you want to chuck your logs into a file with good ‘ol C++. You’ll want to include the <iostream> and <fstream> libraries to do file operations. Here’s a quick example:

#include <iostream>
#include <fstream>
#include <string>

int main() {
    std::ofstream logFile("appLog.txt", std::ios::app);  // Open in append mode

    if (!logFile.is_open()) {
        std::cerr << "There was a problem opening the log file!" << std::endl;
        return 1;
    }

    logFile << "Application started" << std::endl;
  
    // ... somewhere in your app logic
    logFile << "An important event has occurred" << std::endl;

    // Don't forget to close your file stream
    logFile.close();

    return 0;
}

If you tail your log file with tail -f appLog.txt, you should see:

Application started
An important event has occurred

Neat, you’ve got a timestamped record of events!

Deep Dive

Logging is as old as computing itself, with roots in literal marks on paper to trace what ancient computers were up to. In the modern era, it’s all about sophisticated software solutions. You’ve got straight-to-file logging, like the quick and dirty example above, or you might indulge in a fancier logging framework, such as Log4cpp or Boost.Log in the C++ realm; these bad boys offer logging levels, format control, and more.

Speaking of levels, logging best practices include using varying levels of severity—info, debug, warning, error, fatal—so you can filter the noise when you’re trying to squash bugs or figure out why your app’s behaving like a moody teenager.

On the performance note, don’t get sloppy with your logs. Excessive logging can turn your lightning-fast app into a snail marathon, bog down file systems, or even cost you bucks in storage fees if you’re cloud-based. Striking the right balance is key: log what you need, and nothing more.

See Also

For those of you who like to go the extra mile with your logging practices, check these out:

• The Boost.Log Library for some heavy-duty logging features.
• Google’s glog library if you’re into what the tech giant’s cooks are using to log their apps.
• The Log4cpp library for a configurable logging mechanism.

And for a bit of background reading on the whys and hows of logging, dive into:

• This Stack Overflow thread on logging best practices will give you a peer-reviewed deep dive into the subject.