What is vsnprintf

vsnprintf_s() prints a formatted list of arguments to a character array. The vsnprint_s() function validates the arguments at runtime before printing them. The declaration for vsnprintf_s() is shown below:

int vsnprintf_s(char *arr, size_t len, const wchar_t *format, va_list args);

Parameters

arr: Pointer to the character array where output is to be printed.
len: Maximum number of characters that can be written to the array.
format: Format in which the output will be printed.
args: Pointer to the list of arguments to be printed.

Return value

If the write operation to the output stream is successful, vsnprintf_s() returns the number of characters written. A negative value is returned if there is an error when writing to the output stream.

Note: The return value of vsnprintf_s() does not count terminating null characters.

Example

Consider the code snippet below, which demonstrates the use of vsnprintf()_s:

#include <stdio.h>
#include <stdarg.h>
int writeformatted(char* buffer, int bufferSize, const char *format, ...)
{
    int len = 0;
    va_list arguments;
    va_start(arguments, format);
    len = vsnprintf_s(buffer, bufferSize, format, arguments);
    va_end(arguments);
    return len;
}
int main ()
{
    char buf[50];
    char s1[50] = "vsnprintf() Example Code";
    int len = writeformatted(buf, 50, "%s ", s1);
    printf("Content of array: %s \n", buf);
    printf("No. of characters in array: %d \n", len);
    return 0;
}

What is vsnprintf_s() in C?

Parameters

Return value

Example

Output

Explanation