C: Passing variable number of arguments from one function to another

Question

So, here's a small problem I'm facing right now -> I'm trying to write a function that will accept a char* message and a variable number of arguments. My function will modify the message a little, and then It'll call printf with the message and given parameters. Essentialy, I'm trying to write something like that:

void modifyAndPrintMessage(char* message,...){
    char* newMessage; //copy message.
    //Here I'm modifying the newMessage to be printed,and then I'd like to print it. 
    //passed args won't be changed in any way.

    printf(newMessage,...); //Of course, this won't work. Any ideas?
    fflush(stdout);

}

So, anybody knows what should I do to make it happen? I'd be most grateful for any help :)

Answer 1

You want to use varargs...

void modifyAndPrintMessage( char* message, ... )
{
    // do somehthing custom

    va_list args;
    va_start( args, message );

    vprintf( newMessage, args );

    va_end( args );
}

Answer 2

void modifyAndPrintMessage(char* message,...)
{   char newMessage[1024]; // **Make sure the buffer is large enough**
    va_list args;
    va_start(args, message);
    vsnprintf(newMessage, message, args);
    printf(newMessage);
    fflush(stdout);
}