Question

Does someone know how to write a program in C with the verbose option (the option to choose if messages are printed or not) in a nice way.

I mean, not writing an if(verbose) for each printf in the code.

Is there a more elegant solution?

Answer 1

Just use a (variadic) macro / vararg function that tests a flag before calling something like vfprintf.

/* Crude example. */
void my_log(char *format, ...)
{
    va_list args;
    if (!ok_to_log)
        return;

    va_start(args, format);
    vprintf(format, args);
    va_end(args);
}

EDIT As requested

How about a slightly modified gnu example:

#define eprintf(format, ...) do {                 \
    if (ok_to_print)                              \
        fprintf(stderr, format, ##__VA_ARGS__);   \
} while(0)