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// The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
/*
This is an example showing how to control where the dlib::logger sends its messages.
This is done by creating a "hook" class that is called whenever any of the loggers want
to log a message. The hook class then outputs the messages using any method you like.
Prior to reading this example, you should understand the basics of the dlib::logger.
So you should have already read the logger_ex.cpp and logger_ex_2.cpp example programs.
*/
#include <dlib/logger.h>
using namespace dlib;
using namespace std;
class my_hook
{
public:
my_hook(
)
{
fout.open("my_log_file.txt");
}
void log (
const string& logger_name,
const log_level& ll,
const uint64 thread_id,
const char* message_to_log
)
{
// Log all messages from any logger to our log file.
fout << ll << " ["<<thread_id<<"] " << logger_name << ": " << message_to_log << endl;
// But only log messages that are of LINFO priority or higher to the console.
if (ll >= LINFO)
cout << ll << " ["<<thread_id<<"] " << logger_name << ": " << message_to_log << endl;
}
private:
ofstream fout;
};
int main()
{
my_hook hook;
// This tells all dlib loggers to send their logging events to the hook object. That
// is, any time a logger generates a message it will call hook.log() with the message
// contents. Additionally, hook.log() will also only be called from one thread at a
// time so it is safe to use this kind of hook in a multi-threaded program with many
// loggers in many threads.
set_all_logging_output_hooks(hook);
// It should also be noted that the hook object must not be destructed while the
// loggers are still in use. So it is a good idea to declare the hook object
// somewhere where it will live the entire lifetime of the program, as we do here.
logger dlog("main");
// Tell the dlog logger to emit a message for all logging events rather than its
// default behavior of only logging LERROR or above.
dlog.set_level(LALL);
// All these message go to my_log_file.txt, but only the last two go to the console.
dlog << LDEBUG << "This is a debugging message.";
dlog << LINFO << "This is an informational message.";
dlog << LERROR << "An error message!";
}
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