constructing filename string at runtime

[drsmooth]

i need to open a file whose name i only know part of until runtime.

it is based on a char value.
the char represents gender and is either 'm' or ''f'

i need to load from a text file called names_m.txt or names_f.txt but i don't know until runtime.

i tried this but it didnt quite work...

 char fileName[18] = {"/data/names_"};
  fileName[13] = gender;
  fileName[14] = '.';
  fileName[15] = 't';
  fileName[16] = 'x';
  fileName[17] = 't';
  fileName[18] = '\0';

i want to use an fstream to open the file in the folder 'data' at the working directory

[Firecore]

You couls use something like the sprintf() function.
I think that formats strings like printf except instead of printing them, it saves the string in a variable.

Look it up in MSDN for more info.

I think it mite help u.

[drsmooth]

actually i ran through it and the problem seems to be in the "/data/" part...is there something wrong with the way i access the file...

like i need to access the folder 'data' in the working directory

[Studlyami]

I would use a string as a variable (are you unable to do this for some reason).

string Test = "data//names_";
Test += gender;
Test +=".txt";
 
FILE * f_ptr;
 
f_ptr = fopen(Test.c_str(), <flags>);
 

Another problem is the /data/filename

you need "data//names_" a single line is used for special operations like new line \n.

[Ganon11]

Studlyami, why use a FILE* in C++? If strings are available, then so are ifstreams and ofstreams.

Then again, if it's not C++ but C, then strings are not available, and you must use a char array.

Something else I see wrong is the fact that you declare filename to be 18 chars long (with indeces 0-17), but then try to use fileName[18] (which is out of bounds).

[Studlyami]

I guess because its what I'm comfortable with. If you can't use strings add a second / to you array and change the size appropriately and it should work.

[oler1s]

I guess because its what I'm comfortable with.

That's a poor excuse. You'll turn everything into a nail because you can only use a hammer?

[Studlyami]

I know it is. It was more of a problem of ignorance than laziness. Thats one of the reasons why i stay around this site. Theres always room for improvement.

[drsmooth]

could someone maybe show me an example of this with the fstream or ifstream?

i tried this:

void Civilian::assignName()
{
 string test = "data//names_";
 test += gender;
 test +=".txt";
 fstream file(test, ios::in);
 string g;
 file>>g;
 cout<<g;
}

but i must have set up the fstream wrong i got:

[C++ Error] Civilian.cpp(36 ): E2285 Could not find a match for 'fstream::basic _fstream(string ,enum)'

[Studlyami]

As you read above i havn't used ifstream or ofstream, but here is a reference on how to use these two streams .