Question

I would like to modify the function printf to a new function printf2 that simply prepends the message to be printed with Hello.

I could do

void printf2(char message[]) {
    printf("Hello ");
    printf(message);
}

The problem is that I cannot pass the extra arguments for cases when message has %d, %c, etc.

How can I have printf2 accept as many parameters printf can, and pass them on to printf?

Answer 1

The comment above points you in the right direction, but here is an example of how to prepend your tag (Hello).

Notes:
I have used the s and n version of printf to format a new string that shouldn’t overflow my temp buffer, and *MAX_MSG_SIZE* is assumed to be defined appropriately elsewhere.

void printf2(const char *format, ...)
{

    char buffer[MAX_MSG_SIZE] = "";  


    va_list args;


    va_start(args,format);
    vsnprintf(buffer, MAX_MSG_SIZE, format, args);
    va_end(args);   

    printf("Hello: %s\n", buffer);
}