strcat problem

[hebes_99]

Thanks for the support CJ!

In responce to the string class / library, I tried to use that, but can't seem to get it to work.

#include<string>

void test()
{

string str;
str = "This is a test";

}


this returns the following
error C2065: 'string' : undeclared identifier (among other errors..)

I also tried #include <string.h> ...so, I gave up on this. But I do know that the string class would solve a lot of my problems!

[CJ1]

Well, this is just wrong! The "%.5d" does NOT limit the output - go check your manuals. It is responsibility of the programmer to provide enough room in the destination buffer (that is why printf's are not safe).

You better read your manual more carefully and concentrate on the precision field

From MSDN:
The third optional field of the format specification is the precision specification. It specifies a nonnegative decimal integer, preceded by a period (.), which specifies the number of characters to be printed, the number of decimal places, or the number of significant digits (see the How Precision Values Affect Type table). Unlike the width specification, the precision specification can cause either truncation of the output value or rounding of a floating-point value.

that is how you limit the output size.

Also, even if this code compiles in C++ compiler, it still has nothing to do with C++. But I do think that it was OK to post the question here.

Again read the C++ specification, it includes most of C as part of C++ (there are some minor differences), so the code is both valid C & C++ code just like a = b + c; is valid in C, C++, C#, PASCAL, etc.

I am surprised that nobody pointed out an obvious OP's misunderstanding:

char *fp = strcat(filepath,strcat(filesuffix,bunotostring));

strcat appends (concatenates) second string to the first string, returning pointer to the target (first string). It does NOT allocate any new memory for char* fp! In that example, fp is equal to filepath. And filepath buffer is not capable to accept all other strings at its end.

Sorry that is not correct, strncat (as well as the other str... functions) return a pointer to the destination (argument 1) for just that reason it can be used where the calls can be chained. fp will end up pointing to filepath which has a reserved size, same thing for filesuffix which also has a reserved size.

Here comes C++, that provides string classes that take care of the memory management (like std::string and MFC's CString), so you no longer need to guess if 64 bytes will be enough for the file path (you know, it won't).

While 64 is below the maximum possible size file a path it is within the limits presented in the example.

[Mick]

Thanks for the support CJ!

In responce to the string class / library, I tried to use that, but can't seem to get it to work.

#include<string>

void test()
{

string str;
str = "This is a test";

}


this returns the following
error C2065: 'string' : undeclared identifier (among other errors..)

I also tried #include <string.h> ...so, I gave up on this. But I do know that the string class would solve a lot of my problems!

string is located in the std namespace. Either use:
using namespace std;
to promote the library names to the current namespace
or
std::string str;

[Mick]

As to everyone else...Take a deep breath, turn to the person to your right, and give them a big hug.

[hebes_99]

Thanks! That helped with the identifier part...BUT...now I get..

error C2872: 'ifstream' : ambiguous symbol

in which ifstream worked before I used namespace...



HOWEVER, std::stream str; worked fine...Thanks !!! I am glad for the help... Hopefully, in a few months, I will have a better handle on all of this!

[Mick]

Your mixing the older headers with the new headers.

http://msdn.microsoft.com/library/de...ementation.asp

http://msdn.microsoft.com/library/de...ementation.asp

[hebes_99]

Thanks again....

wow...much to learn....

[Mick]

Thanks again....

wow...much to learn....

Search the forum for "books" or "c++ books" there are many recommendations, there is also a listing of books in the C++ faq forum.

In short...getting a C++ book will facilitate your learning.

[VladimirF]

Well, Mick - I did hug the person to my right. May I respond now?

You better read your manual more carefully and concentrate on the precision field

If you follow your link a little further "(see the How Precision Values Affect Type table)", you would see:

d, i, u, o, x, X The precision specifies the minimum number of digits to be printed. If the number of digits in the argument is less than precision, the output value is padded on the left with zeros. The value is not truncated when the number of digits exceeds precision.

that is how you limit the output size.

Do you? Did you try?

Sorry that is not correct, strncat (as well as the other str... functions) return a pointer to the destination (argument 1) for just that reason it can be used where the calls can be chained...

So, what is not correct?

My point, however, was that OP might believe that he would get a new string with the result of strcat() in it. (Otherwise, why would he need another variable?) That, of course, was a guess. I am ready to bet a quarter I was right, though.

[CJ1]

Right you are on the precision field, my error.

As for the quarter, I wouldn't want to guess or assume the intentions.

This point only undelines that C++ is NOT a language for beginners, it is much too easy to get caught by all the subtleties (like if the intention was to get a new string or just a pointer), but you can't beat C++ for its power!

[Paul McKenzie]

To hebes 99,

The problem seems to have started with learning 'C' before learning C++.

Somehow you stumbled onto strcat(), but this should have been the last function to use. C++ has a string class (as you now know), that should be introduced early, maybe sometimes in the first couple of lessons, of learning C++. All of those strcats, strcpys, etc. are not necessary for general purpose C++ programming.

Also, in C++, pointers are less used and should be avoided unless you have to use them. I suggest you get a C++ (and only a C++) book such as "Accelerated C++" by Koenig & Moo. Do not read C books or tutorials to learn C++.

http://www.parashift.com/c++-faq-lit....html#faq-28.2

Regards,

Paul McKenzie

[CJ1]

I agree, BUT I still think C++ is NOT a good first language. Also C# is a better introduction to C++ than C, and it would has the added advantage of protecting the beginner from system crashing errors.

We have moved to C# for everyting that doesn't require C or C++, and when we require C or C++, we give that job to the senior developers only.

The C# language is simple to learn, the .NET framework on the other hand is a mountian.

[VladimirF]

I agree, BUT I still think C++ is NOT a good first language.

I think that C++ is the ONLY language for Windows development. That makes it a very good first language (because there are no other languages).

We have moved to C# for everything that doesn't require C or C++, and when we require C or C++, we give that job to the senior developers only.

Do you have any openings?

[cilu]

Seems that I missed all the fun yesterday. And missed that hug also...

VictorN is wrong is saying there is no specific C++ code as all the code you presented was valid C++ code, perhaps it should have been posted in the C++ (Non Visual C++ Issues) forum.

Original code posted:

int buno = 0;
char filepath[64] = "C:\\some path here\\";
char filesuffix[32] ="_flt_test.csv";
char bunotostring[5] = "123456"; 

// Convert buno number (int) to string
sprintf(bunotostring, "%d", buno);

char *fp = strcat(filepath,strcat(filesuffix,bunotostring));

As I stated in my first post in this thread, there is nothing C++ specific, except for declaration char* fp, which in C should be made at the beginning of the block. Hebes said he is new to C++,

First of all, somewhat newbie to C++.

so I presumed he comes from the C field. And the code was just C, even if as CJ says is valid C++ code (which of course is).

I agree, BUT I still think C++ is NOT a good first language.

I think that the first language to start with is Pascal. It was intended as a teaching language. Then you switch C and C++. This is my personal opinion.