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Why strncpy(s, t, n) doesn't put '\0' at the end?

I am a C programming beginner...
I wonder, why strncpy(s, t, n) does not put '\0' at the end of the string.
Because when I output the copied string, it output more than what I want,
until I put '\0' at the end by myself.

But, sometime I don't need put '\0' and it work well??
Like
strncpy(s, t, n);
strcat(s, t1);
.....
work just what I want.

Nov 14 '05
12 15706
"Joe Wright" <jo********@ear thlink.net> wrote in message
news:40******** ***@earthlink.n et...
Peter Pichler wrote:
"CBFalconer " <cb********@yah oo.com> wrote in message
news:40******** *******@yahoo.c om...
Why not simply write:

strncpy(dst, src, n-1); dst[n] = '\0';
ITYM
strncpy(dst, src, n); dst[n-1] = '\0'; /* copies one char too many */ or
strncpy(dst, src, n); dst[n] = '\0'; /* or n-1, depending on n

*/
Not so. Given the array dst[10] the element dst[10] does not exist.


In that case, n == 9. That's why I said, "depending on n".
Nov 14 '05 #11
CBFalconer <cb********@yah oo.com> wrote:
Richard Bos wrote:
Why use a non-Standard solution when

dest[0]='\0'; strncat(dest, src, n);

works just as well?
Because you have to pay peculiar attention to the value of n,


Peculiar? What's so unusual about having to know the length of the
memory area you're copying into? You _have_ to pass this length, or else
you're back with plain strcpy().
and the result doesn't tell you when something has been truncated.


That isn't always something you care about; and in any case, the
original strncpy() call doesn't give you that information, either.

Richard
Nov 14 '05 #12
Richard Bos wrote:

CBFalconer <cb********@yah oo.com> wrote:
Richard Bos wrote:
Why use a non-Standard solution when

dest[0]='\0'; strncat(dest, src, n);

works just as well?


Because you have to pay peculiar attention to the value of n,


Peculiar? What's so unusual about having to know the length of the
memory area you're copying into? You _have_ to pass this length, or else
you're back with plain strcpy().
and the result doesn't tell you when something has been truncated.


That isn't always something you care about; and in any case, the
original strncpy() call doesn't give you that information, either.


Then go right ahead and use it. I really don't mind. I don't
want to have to think about things, so the more natural the
parameters are the better. The more info I get back the better,
as long as it isn't misleading info.

--
Chuck F (cb********@yah oo.com) (cb********@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!
Nov 14 '05 #13

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