problem with file function

[Thegame16]

Hey guys I have to functions that I am opening files with and I seem to be doing it wrong.
The first function contains a null terminated string that contains the name of the file.

The second function receives a pointer to the file. I just put the file name because I wasn't sure the correct way to open it with the pointer.

Does anyone know how i can fix these two problems?

#include <cstring>
#include <cstdio>

FILE* open(const char filename[])
{
FILE fp;
   if(fp!=Null)
   {
   fp=fopen("filename","r");//doesnt work
   }

      else
      {
      fp=NULL;
      }
return fp;
}


int registeredA(FILE* fp, int area)
{
fp=fopen("prefix.txt","r");  //I know this is wrong this the file I want to open but dont know how with this function
}

[CommonTater]

The variable filename should not be in quotes...

FILE* open(const char Filename)
 { return fopen(Filename,"r"); }

then...

fp = open("prefix.txt");

Thing is that's such a thin wrapper you might just as well call fopen directly...
fopen returns a file handle or null... so you gain nothing by plumping it out, you still have to check it after it returns.

// your way...
FILE* fp = open("prefix.txt");
if (!fp)
  { printf "file error");
     exit (0); }

// opening it directly
FILE *fp = fopen("prefix.txt");
if (!fp)
  { printf("Holy crap the file didn't open!");
     exit (0); }

See what I mean... the wrapper serves no purpose.

[Thegame16]

The variable filename should not be in quotes...

FILE* open(const char Filename)
 { return fopen(Filename,"r"); }

then...

fp = open("prefix.txt");

Thing is that's such a thin wrapper you might just as well call fopen directly...
fopen returns a file handle or null... so you gain nothing by plumping it out, you still have to check it after it returns.

// your way...
FILE* fp = open("prefix.txt");
if (!fp)
  { printf "file error");
     exit (0); }

// opening it directly
FILE *fp = fopen("prefix.txt");
if (!fp)
  { printf("Holy crap the file didn't open!");
     exit (0); }

See what I mean... the wrapper serves no purpose.

thanks that fixed my first function.

But so the second function:int registeredA(FILE* fp, int area)
The file is being passed by a pointer to it. so it should know the name the name without me
telling it. Correct?

If so how to I open it without saying the direct name and using the pointer.
Something like this fopen("fp","r")?

[Adak]

"fp" is a string containing the letters f and p. It is not a file pointer. If you fopen("fp"...etc.), you will have opened a file named fp.

You want a pointer to the name of the file, or a string literal with the name of the file, not a file pointer itself, as the first parameter for fopen().

[Thegame16]

"fp" is a string containing the letters f and p. It is not a file pointer. If you fopen("fp"...etc.), you will have opened a file named fp.

You want a pointer to the name of the file, or a string literal with the name of the file, not a file pointer itself, as the first parameter for fopen().

so by having this function int registeredA(FILE* fp, int area). The proper way to open the file would be

fp=fopen("prefix.txt","r");

[CommonTater]

so by having this function int registeredA(FILE* fp, int area). The proper way to open the file would be

fp=fopen("prefix.txt","r");

Correct...

C Function Reference - fopen Function