HP-UX Reference (11i v1 05/09) - 5 Miscellaneous Topics (vol 9)

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stdarg(5) stdarg(5)

NAME

stdarg.h - macros for handling variable argument lists

SYNOPSIS

#include <stdarg.h>

void va_start(va_list pvar, argN);

type va_arg(va_list pvar, type);

void va_end(va_list pvar);

DESCRIPTION

The <stdarg.h> header contains a set of macros that can be used to write portable procedures that accept

variable argument lists. Routines that have variable argument lists (such as

printf()) but do not use

stdarg are inherently nonportable, because different machines use different argument-passing conventions.

va_list is a type deﬁned for the variable used to traverse the list.

va_start is called to initialize pvar to the beginning of the list. The type of argN should be the same as the

argument to the function just before the variable portion of the argument list.

va_arg returns the next argument in the list pointed to by pvar. type is the type the argument is expected

to be. Different types can be mixed, but it is up to the routine to know what type of argument is expected,

because it cannot be determined at runtime.

va_end is used to clean up.

Multiple traversals, each bracketed by va_start ... va_end, are possible.

EXAMPLE

This example is a possible implementation of

execl (see exec(2)):

#include <stdarg.h>

#define MAXARGS 100

/* execl is called by

execl(file, arg1, arg2, ..., (char *)0);

execl(const char *file, const char *args, ...)

{

va_list ap;

char *array[MAXARGS];

int argno = 0;

va_start(ap, args);

if ((array[0] = args) != 0)

while ((array[argno++] = va_arg(ap, char *)) != 0)

;

va_end(ap);

return execv(file, array);

}