Header File 

stdio.h 

Category 

Memory and String Manipulation Routines 

Prototype 

int vsnprintf(char* buffer, size_t nsize, const char* format, va_list param); 

int vsnwprintf(wchar_t* buffer, size_t nsize, const wchar_t* format, va_list param); 

Description 

Sends formatted output to a buffer of maximum length specified by nsize. 

If the number of bytes to output is:

• < nsize, then all of the characters have been written, including the terminating ‘\0’ character.
• == nsize, then nsize characters are written, with no terminating ‘\0’ character.

> nsize, then only nsize characters are written, with no terminating ‘\0’ character. 

If nsize is 0, then the string will not be written to (and may be NULL). 

Return Value 

Number of bytes output, or, if nsize is 0, the number of bytes needed, not including the terminating ‘\0’ character.