varargs(5)

NAME
     varargs - Variable argument list

SYNOPSIS
     "#include <varargs.h>"

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

IMPLEMENTATION
     IRIX systems

DESCRIPTION
     NOTE: varargs is being replaced by stdarg(5).  See the stdarg(5) man
     page for the recommended method of passing variable argument lists.

     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, because 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.

EXAMPLES
               #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.

SEE ALSO
     stdarg(5)