In conjuntion with vsprintf
<stdarg.h> in conjunction with
vsprintf allows to write a
printf function that automatically prepends the written string with a timestamp:
#include <stdarg.h>
#include <stdio.h>
#include <time.h>
void printfWithTimestamp(char* fmt, ...) {
va_list args;
char buf[256]; // 256 bytes should be enough for anyone...
va_start(args, fmt);
vsprintf(buf, fmt, args);
va_end(args);
time_t t = time(NULL);;
struct tm *tm = localtime(&t);
printf("%4d-%02d-%02d %02d:%02d:%02d | ", tm->tm_year+1900, tm->tm_mon+1, tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
printf(buf);
printf("\n");
}
int main() {
printfWithTimestamp("The number is %d, the text is %s.", 42, "Hello world");
sleep(3);
printfWithTimestamp("Three seconds later.");
}