C in a Nutshell

Name

vfprintf, vprintf, vsnprintf, vsprintf

Synopsis

Writes formatted output using a variable argument list object

#include <stdio.h>
#include <stdarg.h>
intvfprintf( FILE * restrict fp, const char * restrict format,
              va_list argptr );
int vprintf( const char * restrict format, va_list argptr );
int vsprintf( char * restrict buffer, const char * restrict format,
              va_list argptr );
int vsnprintf( char * restrict buffer, size_t n,
               const char * restrict format, va_list argptr );  (C99)

The functions vfprintf(), vprintf(), vsprintf(), and vsnprintf() work in the same way as fprintf(), printf(), sprintf(), and snprintf(), respectively, except that their last argument, argptr, is a variable-argument list object with type va_list. The program must initialize this object by calling the va_start() macro before calling the vfprintf(), vprintf(), vsprintf(), or vsnprintf() function, and must call the va_end() macro after the function returns. Because these functions use the va_arg() macro internally to advance argptr through the argument list, its value is indeterminate after the vfprintf(), vprintf(), vsprintf(), or vsnprintf() function call has returned.

Tip

The va_start(), va_arg(), and va_end() macros and the type va_list are declared in the header file stdarg.h.

Like the fprintf() and printf() functions, vfprintf() and vprintf(), return the number of characters written to the output stream. The function vsprintf() returns the number of characters written to the string buffer, not counting the terminator ...