vprintf() - I/O Function

Tutorials

Cpp

Topic

How is "vprintf()" used in C++?

Explanation

vprintf() is an I/O function that writes the contents of the format string to the stdout with a pointer to a list of arguments replacing the argument list. The total number of characters are returned by this function, but on failure a negative number is returned.

Syntax:

    int vprintf ( const char * format, va_list arg );

The following table lists the type specifier used with vprintf()

Type	Description
c	Character
d or i	Signed decimal integer
e	Scientific notation using e character
E	Scientific notation using E character
f	Decimal floating point
g	Use the shorter of %e or %f
G	Use the shorter of %E or %f
o	Signed octal
s	String of characters
u	Unsigned decimal integer
x	Unsigned hexadecimal integer
X	Unsigned hexadecimal integer(capital)
p	Pointer address
%	A % followed by another % character will write % to the stream.

Example:

   #include <stdio.h>
   #include <stdarg.h>
   
   void Form (char * format, ...)
    {
      va_list args;
      va_start (args, format);
      vprintf (format, args);
      va_end (args);
    }
   
   int main ()
    {
      Form ("Function with %d variable argument.\n",1);
      Form ("Function with %d variable %s.\n",2,"arguments");
      return 0;
    }

Result:

    Function with 1 variable argument.
    Function with 2 variable arguments.

In the above example vprintf() is used to call a function with different number of arguments.