Variable Argument

It’s possible to create functions that receive an unspecified number of arguments. Most programs in the text have used the standard library function printf which, as you know, takes a variable number of arguments. As a minimum, printf must receive a string as its first argument, but printf can receive any number of additional arguments.

The function prototype for printf is

int printf( const char *format, ... );

 

The ellipsis (…) in the function prototype indicates that the function receives a variable number of arguments of any type. The ellipsis must always be placed at the end of the parameter list. The macros and definitions of the variable arguments headers <stdarg.h> provide the capabilities necessary to build functions with variable-length argument lists. Here, demonstrates function average that receives a variable number of arguments. The first argument of average is always the number of values to be averaged.