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"Nicolas" <> wrote in message
news:3fbfeb99$0$27046$...
> On most implementations of the standard C library, the functions that
> copy characters in a previously allocated buffer, like strcpy or strcat,
> are returning the pointer to that buffer.
>
> On my NetBSD system, man strcpy gives the following prototype :
> char *strcpy(char * restrict dst, const char * restrict src);
>
> What's the point in returning a pointer we already know before the call?
>
> Thank you in advance for an explanation.

So that you can write (unnecessarily abbreviated) code like this:

strcat(path, strcpy(file, "fred.txt"));

On most implementations of the standard C library, the functions that
copy characters in a previously allocated buffer, like strcpy or strcat,
are returning the pointer to that buffer.

On my NetBSD system, man strcpy gives the following prototype :
char *strcpy(char * restrict dst, const char * restrict src);

What's the point in returning a pointer we already know before the call?

Thank you in advance for an explanation.

"Nicolas" <> wrote in message
news:3fbfeb99$0$27046$...
> On most implementations of the standard C library, the functions that
> copy characters in a previously allocated buffer, like strcpy or strcat,
> are returning the pointer to that buffer.
>
> On my NetBSD system, man strcpy gives the following prototype :
> char *strcpy(char * restrict dst, const char * restrict src);
>
> What's the point in returning a pointer we already know before the call?

Convenience. The result of one of these function calls might
be used as part of a larger expression, e.g.:

printf("%s\n", strcat(s1, s2));

If you don't need the return value, just ignore it.

strcat(s1, s2);

-Mike

Nicolas wrote:
>
> On most implementations of the standard C library, the functions
> that copy characters in a previously allocated buffer, like strcpy
> or strcat, are returning the pointer to that buffer.
>
> On my NetBSD system, man strcpy gives the following prototype :
> char *strcpy(char * restrict dst, const char * restrict src);
>
> What's the point in returning a pointer we already know before the
> call?

It allows you to be baffled by the peculiar run-time actions of:

char p[100] = "Fred";
....
printf("%s or %s\n", p, strcat(p, " and George"));

For improved semantics look up the (non-standard) strlcat and
strlcpy functions.

--
Chuck F () ()
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net> USE worldnet address!

Nicolas wrote:
> On most implementations of the standard C library, the functions that
> copy characters in a previously allocated buffer, like strcpy or strcat,
> are returning the pointer to that buffer.

On ALL implementations. If an implementation were to do something
different, it would no longer be an implementation of the *standard* C
library.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

CBFalconer <> writes:

> It allows you to be baffled by the peculiar run-time actions of:
>
> char p[100] = "Fred";
> ....
> printf("%s or %s\n", p, strcat(p, " and George"));

That code has undefined behavior, you know.
--
"The expression isn't unclear *at all* and only an expert could actually
have doubts about it"
--Dan Pop

Nicolas wrote:

> Jarmo wrote:
>> "Nicolas" <> wrote in message
>> news:3fbfeb99$0$27046$...
>>
>>>On most implementations of the standard C library, the functions that
>>>copy characters in a previously allocated buffer, like strcpy or strcat,
>>>are returning the pointer to that buffer.
>>>
>>>On my NetBSD system, man strcpy gives the following prototype :
>>>char *strcpy(char * restrict dst, const char * restrict src);
>>>
>>>What's the point in returning a pointer we already know before the call?
>>>
>>>Thank you in advance for an explanation.
>>
>>
>> So that you can write (unnecessarily abbreviated) code like this:
>>
>> strcat(path, strcpy(file, "fred.txt"));
>
> Lol, of course this is obvious.
> That's because I never (well almost) enclose a call in another call.

It's probably wise to never (well almost) enclose a call in another call.
Many functions return error indicators which can be missed by such an
approach.

--
Richard Heathfield :
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton

Jarmo wrote:
> "Nicolas" <> wrote in message
> news:3fbfeb99$0$27046$...
>
>>On most implementations of the standard C library, the functions that
>>copy characters in a previously allocated buffer, like strcpy or strcat,
>>are returning the pointer to that buffer.
>>
>>On my NetBSD system, man strcpy gives the following prototype :
>>char *strcpy(char * restrict dst, const char * restrict src);
>>
>>What's the point in returning a pointer we already know before the call?
>>
>>Thank you in advance for an explanation.
>
>
> So that you can write (unnecessarily abbreviated) code like this:
>
> strcat(path, strcpy(file, "fred.txt"));
>
>

Lol, of course this is obvious.
That's because I never (well almost) enclose a call in another call.
Thx.

"Ben Pfaff" <> wrote:
> CBFalconer <> writes:
> > It allows you to be baffled by the peculiar run-time actions of:
> >
> > char p[100] = "Fred";
> > ....
> > printf("%s or %s\n", p, strcat(p, " and George"));
>
> That code has undefined behavior, you know.

It does? Sorry, I don't get it.

Assuming you make it into a complete program:

#include <stdio.h>
#include <string.h>

int main(void)
{
char p[100] = "Fred";
printf("%s or %s\n", p, strcat(p, " and George"));
return 0;
}

--
Simon.

Richard Heathfield wrote:
>
> Nicolas wrote:
>
> >>
> >> strcat(path, strcpy(file, "fred.txt"));
> >
> > Lol, of course this is obvious.
> > That's because I never (well almost) enclose a call in another call.
>
> It's probably wise to never (well almost) enclose a call in another call.
> Many functions return error indicators which can be missed by such an
> approach.
>
But surely many (most?) are expressions with value. I would use the
trick above without batting an eye. I some string manipulation stuff I
wrote..

char *ltrim(char *s); /* remove leading whitespace, return s */
char *rtrim(char *s); /* remove trailing whitespace, return s */

char *alltrim(char *s) {
return ltrim(rtrim(s));
}
--
Joe Wright http://www.jw-wright.com
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---