Format a character string array.

This function is compatible with the following targets:

ANSI

BeOS

EMB/RTOS

Mac OS

Palm OS

Win32

#include <stdarg.h>

#include <stdio.h>

int vsnprintf(char * s, size_t n, 

Parameters for this facility are:

s	char *	A string to write to
n	size_t	Max number of chars to be written to s
format	const char *	The format string
arg	va_list	A variable argument list

The vsnprintf() function works identically to snprintf(), except that the variable list of arguments that can be passed to snprintf() is replaced by an array arg of type va_list, which must have been initialized by the va_start() macro from the stdarg.h header file. The vsnprintf() does not invoke the va_end macro. If n is zero nothing is written; otherwise, any characters beyond the n-1st are discarded rather than being written to the array and a null character is appended at the end.

For specifications concerning the output control string and conversion specifiers please see: "Output Control String and Conversion Specifiers."

Vsnprintf() returns the number of characters that would have been assigned to s, had n been sufficiently large, not including the null character or a negative value if an encoding error occurred. Thus, the null-terminated output will have been completely written if and only if the returned value is nonnegative and less than n.

"Wide Character and Byte Character Stream Orientation"

"printf"

"sprintf"

"Overview of stdarg.h"

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

int sp(char *, size_t, char *, ...);

int main()
{	
	int i = 1;
	static char s[] = "Metrowerks";
	char dest[50];
	int retval;

	retval = sp(dest, 5, "%s is number %d!", s, i);
	printf("n too small, dest = |%s|, retval = %i\n", dest, retval);
	retval = sp(dest, retval, "%s is number %d!", s, i);
	printf("n right size, dest = |%s|, retval = %i\n", dest, retval);

	return 0;
}

// sp() formats and outputs a variable number of arguments
// to a character string using the vsnprintf() function
int sp(char * s, size_t n, char *format,...)
{
	va_list args;
	int retval;
	
	va_start(args, format);		// prepare the arguments
	retval = vsnprintf(s, n, format, args); 
	va_end(args);					// clean the stack
	return retval;
}
Output:
n too small, dest = |Metr|, retval = 23
n right size, dest = |Metrowerks is number 1|, retval = 23





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Last updated: August 16, 2000