Re: comparing char to other known char's

[Eric Bambach <eric@cisu.net>]

On Thursday 23 June 2005 03:40 pm, James Colannino wrote:
> Adrian Popescu wrote:
> > On Thursday 23 June 2005 02:22, James Colannino wrote:
> >>Hey everyone.  I hope this isn't a stupid question.  I've been googling
> >>around trying to find a function that I can use but haven't been
> >>successful.  Here's what I want to be able to do:
> >>
> >>let's say I have a char called 'character.'  I want to compare
> >>'character' to see if it's any one of the characters in a list.  For
> >>example, maybe I would want to test character to see if it's either 'e',
> >>'r', '*', etc.
> >>
> >>Is this easy enough to implement?  I could do if (character == 'e' ||
> >>character == [...] and so on and so forth, but this seems much to
> >>tedious and unreadable to be my only solution.  If anyone has any ideas
> >>I'd be extremely grateful :)  Thanks very much in advance.
> >>
> >>James
> >
> > the way you put it ( if (character == 'e' || ....) ; it is TRUE if
> > any (or only one) from those chars exists ;
>
> I know.  That's what I wanted.  Basically, I want to check to see if
> each character in a string matches any one of an illegal set of
> characters.  Thus, the function would fail if it encountered an illegal
> character in the string.
>
> James

Generally speaking (in terms of input validation), its better practice to 
check against a LEGAL set of characters rather than an illegal set. That way 
you can get all the characters you need, but everything else is blocked. If 
you block illegal ones you're bound to miss a few or even ones from extended 
charsets and input methods that you might not have thought of that could 
wreck havoc in your program.

HTH!

-- 
----------------------------------------
--EB

> All is fine except that I can reliably "oops" it simply by trying to read
> from /proc/apm (e.g. cat /proc/apm).
> oops output and ksymoops-2.3.4 output is attached.
> Is there anything else I can contribute?

The latitude and longtitude of the bios writers current position, and
a ballistic missile.

                --Alan Cox LKML-December 08,2000 

----------------------------------------
-
To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html