NAME
vprintf(), vfprintf(), vsprintf(), vsnprintf() — print formatted output of a varargs argument list
SYNOPSIS
#include <stdarg.h>
#include <stdio.h>
int vprintf(const char *__restrict format, va_list ap);
int vfprintf(FILE *__restrict stream, const char *__restrict format,
va_list ap);
int vsprintf(char *__restrict s, const char *__restrict format,
va_list ap);
int vsnprintf(char *__restrict s, size_t maxsize,
const char *__restrict format, va_list ap);
DESCRIPTION
vprintf(),
vfprintf(),
vsprintf(),
and
vsnprintf()
are the same as
printf(),
fprintf(),
sprintf(),
and
snprintf()
respectively, except that
instead of being called with a variable number of arguments,
they are called with an argument list as defined by
<stdarg.h>.
RETURN VALUE
Each function returns the number of bytes transmitted (excluding the
\0
null byte character in the case of
vsprintf())
or a negative value if an output error was encountered.
By default,
vsnprintf()
returns a negative value if
maxsize
is smaller than the number of characters formatted.
In the UNIX 2003 standards environment (see
standards(5))
it returns the
number of bytes that would have been written to buffer
s,
excluding the terminating null byte,
if
maxsize
had been sufficiently large.
EXAMPLES
The following demonstrates how
vfprintf()
could be used to write an error routine:
#include <stdarg.h>
#include <stdio.h>
.
.
.
/*
* error should be called using the form:
* error(function_name, format, arg1, arg2...);
*/
/*VARARGS0*/
void
error(va_alist)
va_dcl
{
va_list args;
char *fmt;
va_start(args);
/* print out name of function causing error */
(void)fprintf(stderr, "ERROR in %s: ", va_arg(args, char *));
fmt = va_arg(args, char *);
/* print out remainder of message */
(void)vfprintf(stderr, fmt, args);
va_end(args);
(void)abort( );
}
STANDARDS CONFORMANCE
vprintf(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C
vfprintf(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C
vsprintf(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C
Printable version
