file pointer

This is a discussion on file pointer within the C Programming forums, part of the General Programming Boards category; O.K. to use a file we first need to open it (make a connection in the form of a stream) ...

  1. #1
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    file pointer

    O.K. to use a file we first need to open it (make a connection in the form of a stream) this is acheived with fopen which returns a pointer to that file we then assign this returned pointer to a file pointer like so.
    FILE *file_ptr;

    file_ptr=fopen(filename,"mode");

    so fopen returns a pointer which in turn is assigned to our pointer therefore is this a pointer to a pointer if so how come we don't need multiple indirection when declaring our file pointer like so FILE **file_ptr;.

    thaks for pointing me in the right direction.

  2. #2
    zen
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    If you had 2 integer's (int a and int b) to copy the contents from one integer to another you'd do -

    a = b;

    If you have two pointers(int* a and int* b) to copy the contents from one to the other you'd do -

    a = b;

    If this was a pointer to a pointer then the statement would look like -

    a = &b;

    which wouldn't work because 'a' has been delcared to store the address of an integer, not a pointer.

    As fopen() doesn't return the address of a FILE pointer, but the FILE pointer itself then the first case is the one that is carried out.
    zen

  3. #3
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    I think fopen returns the address of the file "structure." The value of the address is then assigned to your file pointer, so it is not a pointer to a pointer. It simply contains the address of the file.

  4. #4
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    it returns a pointer, if it stores it into a pointer, no problem!


    Oskilian

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