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

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

       #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);

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

       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(3HEAD)).	The   EXAMPLES
       section	below  demonstrates  the  use  of va_start() and va_end() with

       The macro va_alist() is used as the parameter list in a function	 defi-
       nition,	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() argu-
       ments (arg1,  arg2, ...)	are passed to vfprintf() in the	argument ap.

       The vprintf(), vfprintf(), and vsprintf() functions return  the	number
       of characters transmitted (not including	\0 in the case of vsprintf()).
       The vsnprintf() function	returns	the number  of	characters  formatted,
       that  is,  the number of	characters that	would have been	written	to the
       buffer if it were large enough. Each function returns a negative	 value
       if an output error was encountered.

       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.

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

       The following demonstrates how vfprintf() could be used to write	an er-
       ror 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);
	       (void) abort;

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

       |      ATTRIBUTE	TYPE	     |	    ATTRIBUTE VALUE	   |
       |MT-Level		     |MT-Safe			   |

       printf(3C), attributes(5), stdarg(3HEAD)

SunOS 5.9			  1 Feb	2001			   vprintf(3C)


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