Log management technology in C++

In the software development process, log management is an important factor that must be considered, especially in C language. C is a strongly typed, efficient object-oriented programming language that supports generic programming and templates. It is widely used in operating systems, network communications, game development, etc. During the development process of C applications, developers often need to track and record the internal status and operation of the application in order to discover and solve problems in a timely manner. This article will introduce the log management technology in C, including the basic principles of logging, logging methods, log level settings, and the implementation of logging.

1. Basic principles of logging

The log is a recording system that records program running status, events and error information. In C applications, developers can monitor the running status of the application by recording logs, quickly locate system faults and solve problems. A logging system usually consists of loggers, targets, and filters. The logger is used to record log information, with the goal of outputting the log information to a file, terminal output, or network, while the filter can filter and forward log messages based on log levels or keywords.

2. Logging methods

In C applications, there are usually three ways to implement logging:

1. Use standard output or file output. This method is relatively simple. Developers only need to call standard output or file output-related APIs to output logs to the console or file. However, this method cannot implement functions such as log level and asynchronous output.

2. Use third-party libraries. There are many efficient, stable, and mature third-party log libraries in C, such as log4cxx, log4cpp, glog, etc. These libraries can implement advanced functions such as log level and asynchronous output. Developers can choose the appropriate library according to the needs of the application. integrated.

3. Write your own log processing module. This method requires developers to write their own log processing code to implement advanced functions such as log level and asynchronous output, but it is more complicated and requires developers to have certain programming experience and technical level.

3. Setting the log level

The log level refers to the priority of the log message, usually including debug, info, warn, error and other levels. In applications, only log information with relatively high levels is generally recorded to reduce the size of log files and improve log processing efficiency. In C, we can set different log levels by defining different macros. For example, in the log4cxx library, you can use the following macros to define different log levels:

define LOG_TRACE(msg) LOG4CXX_TRACE(logger,msg)

define LOG_DEBUG(msg) LOG4CXX_DEBUG(logger ,msg)

define LOG_INFO(msg) LOG4CXX_INFO(logger,msg)

define LOG_WARN(msg) LOG4CXX_WARN(logger,msg)

define LOG_ERROR(msg) LOG4CXX_ERROR( logger,msg)

4. Implementation of logging

In C, multi-threading can be used to achieve asynchronous output of log information. By using multi-threading, log processing efficiency can be improved and the blocking time of the application can be reduced. The following is a simple C log management code example:

include "Logger.h"

include <thread>

include <mutex>

include <condition_variable>

include <queue>

using namespace std;

class LogMessage {

public:

LogMessage(int lv, const string& str): level(lv), message(str)

{

}

int level;

string message ;

};

class Logger {

public:

void log(int level, const string& message)

{

if(level < min_level_)

return;

queue_.emplace(level, message);

cv_.notify_all();

}

void run()

{

while(true) {

unique_lock<mutex> lk(mu_);

cv_.wait(lk, [&] {return !queue_.empty();});

LogMessage msg = queue_.front();

queue_.pop() ;

mu_.unlock();

output(msg.level, msg.message);

mu_.lock();

}

}

void output(int lv, const string& msg)

{

switch(lv) {

case 1: cerr << "[TRACE] "; break;

case 2: cerr << "[DEBUG] "; break;

case 3: cerr << "[ INFO] "; break;

case 4: cerr << "[WARN] "; break;

case 5: cerr << "[ERROR] "; break;

default: cerr << "[UNKNOWN LEVEL]"; break;

}

cerr << msg << endl;

}

protected:

mutex mu_;

condition_variable cv_;

queue<LogMessage> queue_;

int min_level_ = 3;

};

Logger logger;

void log(int level, const string& msg)

{

logger .log(level, msg);

}

int main()

{

thread t1(&Logger::run, &logger);

t1.detach();

log(1, "test trace log");

log(2, "test debug log");

log(3, "test info log");

log(4, "test warn log");

log(5, "test error log");

return 0;

}

In the above code, we use a thread pool to asynchronously output log information. There is a dedicated thread that extracts log messages from the message queue and outputs them to the console. Thread synchronization and safe access to message queues are achieved through mutex locks and condition variables.

Conclusion

Log management is an important issue that cannot be ignored in the software development process. As an efficient programming language, C requires an efficient and stable log management system to monitor the operation of the application. Status, quickly and accurately locate faults and solve problems. In C, we can use standard output, third-party libraries, and write our own log processing modules to implement logging. In addition, we can also optimize the efficiency of logging by setting log levels, implementing asynchronous output and other advanced functions.

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