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VARARGS(3)							    VARARGS(3)

NAME
       varargs - variable argument list

SYNOPSIS
       #include <varargs.h>	     /* for BSD programs */

       #include <stdarg.h>	     /* for ANSI programs */

       function(va_alist)
       va_dcl
       va_list pvar;
       va_start(pvar);
       f = va_arg(pvar, type);
       va_end(pvar);

DESCRIPTION
       This set of macros provides a means of writing portable procedures that
       accept variable argument	 lists.	  Routines  having  variable  argument
       lists  (such  as	 printf(3))  that  do  not  use varargs are inherently
       nonportable, since different machines use  different  argument  passing
       conventions.

       va_alist	 is  used  in a function header to declare a variable argument
       list.

       va_dcl is a declaration for va_alist.  Note that there is no  semicolon
       after va_dcl.

       va_list	is  a  type  which can be used for the variable pvar, which is
       used to traverse the list.  One such variable must always be declared.

       va_start(pvar) is called to initialize pvar to  the  beginning  of  the
       list.

       va_arg(pvar, type) will return the next argument in the list pointed to
       by pvar.	 Type is the type to  which  the  expected  argument  will  be
       converted  when	passed	as an argument.	 In standard C, arguments that
       are char or short should be accessed as int, unsigned char or  unsigned
       short  are converted to unsigned int, and float arguments are converted
       to double.  Different types can be mixed, but it is up to  the  routine
       to  know	 what  type  of	 argument  is  expected,  since	 it  cannot be
       determined at runtime.

       va_end(pvar) is used to finish up.

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

EXAMPLE
				     #include <varargs.h>
				     execl(va_alist)
				     va_dcl
				     {
				     va_list ap;
				     char *file;
				     char *args[100];
				     int argno = 0;

				     va_start(ap);
				     file = va_arg(ap, char *);
				     while (args[argno++] = va_arg(ap, char *))
				     ;
				     va_end(ap);
				     return execv(file, args);
				     }

BUGS
       It  is  up to the calling routine to determine how many arguments there
       are, since it is not possible to determine this from the	 stack	frame.
       For  example,  execl  passes a 0 to signal the end of the list.	Printf
       can tell how many arguments are supposed to be there by the format.

       The macros va_start and va_end may be arbitrarily complex; for example,
       va_start	 might contain an opening brace, which is closed by a matching
       brace in va_end.	 Thus, they should only be used where  they  could  be
       placed within a single complex statement.

7th Edition			 May 15, 1986			    VARARGS(3)
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