CODEWITHSUNDEEP
clinux
user1832809
user1832809

Reputation: 81

Application log level

I've seen a lot of applications with different log levels, where you can enable/disable them with the level number you specify.

For example, log level 1 has the most details and outputs a lot of detail. Level 2 has less details, level 3 is even less detailed, and level 4 is to disable logging altogether.

Can you please advise on how to implement that in a C application?

Upvotes: 1

Views: 156

Answers (1)

paxdiablo
paxdiablo

Reputation: 881103

It all basically comes down to the logging function. It will be something like:

#define LOG_ALL       0
#define LOG_DEBUG     1
#define LOG_INFO      2
#define LOG_WARN      3
#define LOG_ERROR     4
#define LOG_FATAL     5
#define LOG_NEXTFREE  6

static unsigned int threshold = LOG_WARN;

void logIt (unsigned int level, char *message) {
    if (level >= threshold)
        puts (message);
}

In other words, the log function will only output a message if the level for that message is sufficient to pass the logging threshold. You call it with things like:

logIt (LOG_INFO, "process starting");
logIt (LOG_FATAL, "cannot read boot sector");

At the default threshold (warning), you will see the latter but not the former.

All you need to add then is a way to modify the threshold dynamically and you can affect what gets logged.

void getAndChangeLevel (unsigned int newLevel) {
    if (newLevel < LOG_NEXTFREE)
        threshold = newLevel;
}

Of course, there's all sorts of other functionality that may be desirable, I've tried to keep the code simple to illustrate the particular concept you asked about.

Upvotes: 2

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