What is wrong here?????

I have run through this code many times, and i cant figure out what's wrong with it! why doesn't it work?? i have isolated it to just the following lines:

Code:

fstream DataFile("data.txt", ios::in | ios::binary);

if(!DataFile)
{
  cout << "No file found!!!\n";
  return 0;
}
else
{
  char* data;
  data = new char;
  char tmp;
  while(DataFile.get(tmp)) strcat(data, &tmp);
  cout << data << endl;
  delete data;
  return 0;
}

my thoughts are maybe something to do with the strcat? also how do i know i am not overrunning something??

I think it might have something to do with

Code:

char* data;
data = new char;

You should do this:

Code:

char* data = new char;

(I think)

but that shouldn't matter? anyways i guess what would be a better idea than just asking 'whats wrong??' would be to kind of explain the code.

main objective:
to replace 5 lines of variable length within a file.

the file is somewhat similar to an ini file, containing any number of definitions in the following format:


<name>
<line1>
...
<line5>

what i need to do is find the name of the current definition as loaded into the memory, then replace the 5 lines that follow it with the program-modified version, and close the file. alternately, if the name is not found, i want to append the name along with the five lines at the end of the file.

now, to my understanding, a file in it's primitive state is simply a string. so, i cant just replace say 10 characters with 15, or i will be overwriting the next line of the file. so i decided to try loading the whole file into memory as a string, and then see what i can do from there. does this seem like a good approach?

--------
added
-------

maybe an array of strings would be better, each string for one line of the file? then when i want to save it back just slap it all back in there in a row?

char* data;
data = new char;
char tmp;
while(DataFile.get(tmp)) strcat(data, &tmp);


You only alocates memory for one char but you try to squeeze in a whole file?

Yes, reading the entire file into memory, making changes as needed in file, and writing back to file is part of basic file handling.

data should be a string, not a single char

since you don't know how many sets of instructions there will be, a list or a vector may be a better container to hold the file contents. While more straighforward with STL strings and lists, this task is also doable with user defined lists and C style strings.

string buffer;
vector<string> fileContents;
ifstream fin("filename.txt");
while (!fin.eof())
{
//use geline for string class to read first line into buffer
//place buffer into vector
if(buffer == targetString)
//change next five lines of input before sending to fileContents
else
//send next five lines of input to fileContents unchanged
}

now write all of fileContents back to filename.

Right after i posted, i began wondering about that whole 'new char' thingie.. realised that would mean i only gots memory for one char. course, making an array would be tough cause i don't know a) how big the file is or even b) how many extra characters i want to put in after modifying it, so anyway I tried using a string and it works fine. I think I am really beggining to almost nearly kinda sorta understand pointers.
anyways thanks for the help, it works pretty good now. talk to you later!