sscanf sequential assignment?

[Stephen R. van den Berg]

Does the Standard say anything about a guaranteed assignment sequence
for sscanf?

i.e.:  char *str,*p,dest[80];

       sscanf(str," %n%s %n",&p,dest,&p);

Will p guaranteed to get it's value from the second '%n' if 'str'
doesn't point to an empty or all whitespace string?

Since we're at it anyway, what about backward portability with older
libraries, do all old libs support the '%n' identifier too?
--
Sincerely,                 berg at marvin.e17.physik.tu-muenchen.de
           Stephen R. van den Berg.
"I code it in 5 min, optimize it in 90 min, because it's so well optimized:
it runs in only 5 min.  Actually, most of the time I optimize programs."