Re: Proper way to input a dynamically-allocated string

Michel Rouzic wrote:
> I know it must sound like a newbie question, but I never really had to
> bother with that before,

Its not. Even experienced programmers seem not to know the proper
answer to this question (hint:fgets() is hardly adequate.)

> [....] and I didn't even find an answer in the c.l.c FAQ

Not much of a surprise there.

> I'd like to know what's the really proper way for input a string in an
> array of char that's dynamically allocated. I mean, I wish not to see
> any such things as char mystring[100]; I don't want to see any number
> (if possible) I just want to declare something like char *mystring; and
> then I don't know how allocate it with just as many chars (with the
> space for the \0 of course) as you get from stdin.

You have to understand, this is a foreign concept to many if not most
of the readers of this newsgroup. Every string container must have a
size, and "the C way" is to declare that size up front. You can search
the archives of this newsgroup to endless examples of this. The C
library is almost completely useless on this issue as well.

> I'd really like to know once for all what's the smartest way of
> inputing strings from stdin and storing them in a way so they take just
> the needed space and I don't want to see any number such as 100 or
> 10,000 or even 4,294,967,296 in my code. Any way it can be done?

You can read my solution to this problem here:

http://www.pobox.com/~qed/userInput.html

The key point is that the C standard library does not provide
provisions for reading a line of dynamically sized string. 1) gets()
is a deterministic overflow and 2) fgets() is inadequate. So no matter
what, for a really correct and useful solution you have to roll your
own algorithm (but it is doable as the link above demonstrates.)

--
Paul Hsieh
http://www.pobox.com/~qed/
http://bstring.sf.net/

.

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