vsprintf() — Print Argument Data to Buffer

Format

#include <stdarg.h>
#include <stdio.h>
int vsprintf(char *target-string, const char *format, va_list arg_ptr);

Language Level

ANSI

Threadsafe

Yes

Locale Sensitive

The behavior of this function might be affected by the LC_CTYPE and LC_NUMERIC categories of the current locale. The behavior might also be affected by the LC_UNI_CTYPE category of the current locale if LOCALETYPE(*LOCALEUCS2) or LOCALETYPE(*LOCALEUTF) is specified on the compilation command. For more information, see Understanding CCSIDs and Locales.

Description

The vsprintf() function formats and stores a series of characters and values in the buffer target-string. The vsprintf() function works just like the sprintf() function, except that arg_ptr points to a list of arguments whose number can vary from call to call in the program. These arguments should be initialized by the va_start function for each call. In contrast, the sprintf() function can have a list of arguments, but the number of arguments in that list is fixed when you compile the program.

The vsprintf() function converts each entry in the argument list according to the corresponding format specifier in format. The format has the same form and function as the format string for the printf() function.

Return Value

If successful, the vsprintf() function returns the number of bytes written to target-string. If an error occurs, the vsprintf() function returns a negative value.

Example

This example assigns a variable number of strings to string and prints the resultant string.

#include <stdarg.h>
#include <stdio.h>
 
void vout(char *string, char *fmt, ...);
char fmt1 [] = "%s  %s  %s\n";
 
int main(void)
{
   char string[100];
 
   vout(string, fmt1, "Sat", "Sun", "Mon");
   printf("The string is:  %s\n", string);
}
 
void vout(char *string, char *fmt, ...)
{
   va_list arg_ptr;
 
   va_start(arg_ptr, fmt);
   vsprintf(string, fmt, arg_ptr);
   va_end(arg_ptr);
}
 
/******************  Output should be similar to: ****************
 
The string is:  Sat  Sun  Mon
*/