vprintf(3C)						   Standard C Library Functions 					       vprintf(3C)

NAME

       vprintf, vfprintf, vsprintf, vsnprintf - print formatted output of a variable argument list

SYNOPSIS

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

       int vprintf(const char *format, va_list ap);

       int vfprintf(FILE *stream, const char *format, va_list ap);

       int vsprintf(char *s, const char *format, va_list ap);

       int vsnprintf(char *s, size_t n, const char *format, va_list ap);

DESCRIPTION

       The  vprintf(),	vfprintf(),  vsprintf()  and vsnprintf() functions are the same as printf(), fprintf(), sprintf(), and snprintf(), respec-
       tively, except that instead of being called with a variable number of arguments, they are called with an argument list as  defined  in  the
       <stdarg.h> header.  See printf(3C).

       The  <stdarg.h>	header	defines  the type va_list and a set of macros for advancing through a list of arguments whose number and types may
       vary. The argument ap to the vprint family of functions is of type va_list. This argument is used with the <stdarg.h>  header  file  macros
       va_start(),  va_arg(),  and  va_end()  (see stdarg(3EXT)). The  EXAMPLES section below demonstrates the use of va_start() and va_end() with
       vprintf().

       The macro va_alist() is used as the parameter list in a function definition, as in the function called  error() in the example below.   The
       macro  va_start(ap,  parmN), where ap is of type va_list and  parmN is the rightmost parameter (just before ...), must be called before any
       attempt to traverse and access unnamed arguments is made. The  va_end(ap) macro must be	invoked  when  all  desired  arguments	have  been
       accessed.  The  argument  list in ap can be traversed again if va_start() is called again after va_end(). In the example below, the error()
       arguments (arg1,  arg2, ...) are passed to vfprintf() in the argument ap.

RETURN VALUES

       Refer to printf(3C).

ERRORS

       The vprintf() and vfprintf() functions will fail if either the stream is unbuffered or the stream's buffer needed to be flushed and:

       EFBIG	       The file is a regular file and an attempt was made to write at or beyond the offset maximum.

EXAMPLES

       Example 1: Using vprintf() to write an error routine.

       The following demonstrates how vfprintf() could be used to write an error routine:

       #include <stdio.h>
       #include <stdarg.h>
       . . .
       /*
	*   error should be called like
	*	  error(function_name, format, arg1, ...);
	*/
       void error(char *function_name, char *format, ...)
       {
	       va_list ap;
	       va_start(ap, format);
	       /* print out name of function causing error */
	       (void) fprintf(stderr, "ERR in %s: ", function_name);
	       /* print out remainder of message */
	       (void) vfprintf(stderr, format, ap);
	       va_end(ap);
	       (void) abort();
       }

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |See below.		   |
       +-----------------------------+-----------------------------+

       The vprintf() and vfprintf() functions are MT-Safe. The vsprintf() and vsnprintf() functions are Async-Signal-Safe.

SEE ALSO

       printf(3C), attributes(5), stdarg(3EXT), attributes(5), standards(5)

NOTES

       The vsnprintf() return value when n = 0 was changed in the Solaris 10 release. The change was based on the SUSv3 specification. The  previ-
       ous behavior was based on the initial SUSv2 specification, where vsnprintf() when n = 0 returns an unspecified value less than 1.

SunOS 5.10							    29 Mar 2004 						       vprintf(3C)