RES: Re[2]: [Dev-C++] stdin reset...

[Daniel K. O. <dan...@ya...>]

 >  >> fflush(stdin);
 >  > Which is not safe. getchar(), fgets(), etc, should be used instead,
 >
 >  and why is that?
 >  I am very interested in code security issues but at least i want to
 >  understand instead of obey them. so what exactly is considered
 >  'unsafe'?



The same reason you shouldn't fflush(2.5), fflush("some string") nor
fflush(a, b, c), you shouldn't fflush(stdin); the standard says that
"fflush()" is for output streams; not input streams, not strings, not
anything else; the non-standard way can work on a particular system, but it
can kill some lives on others.



 >  what I need is a secure way to read as much as there is from stdin
 >  undtil '\n' into a char* buffer. I want that buffer to match the
 >  needed length (I don't know how to do that, since I don't know the
 >  exact needed length until i read it from stdin...) and I need to avoid
 >  buffer overflows (of course).
 >  I thought scanf() is a good way, since it reads only a specified
 >  number of characters right? (ok, this is just a workaround, I guess..)


Try fgets(), then sscanf().


 >  I don't think this is a unique problem so there must be a known way to
 >  solve it, is there?




Suggestion (for all you C programmers):

The comp.lang.c answers to frequently asked questions:
http://www.eskimo.com/~scs/C-faq/top.html







Daniel K. O.