vsnprintf() — Format and print data to fixed length buffer

Standards

Standards / Extensions	C or C++	Dependencies
C99 Single UNIX Specification, Version 3 C++ TR1 C99	both	z/OS® V1R6

Format

#define _ISOC99_SOURCE
#include <stdio.h>
#include <stdarg.h>

int  vsnprintf(char *__restrict__ s, size_t n, 
               const char *__restrict__ format, va_list arg);

General description

Equivalent to snprintf(), except that instead of being called with a variable number of arguments, it is called with an argument list as defined by <stdarg.h>.

Returned value

Returns the number of characters that would have been written had n been sufficiently large, not counting the terminating null character, or a negative value if an encoding error occurred. Thus, the null-terminated output has been completely written if and only if the returned value is nonnegative and less than n.