Question

In this function findBookByTitle what is supposed to happen is fp is opened and if a title matches the one given to function it will print the title. It is assumed titles are unique so once a match is found it can stop searching. My problem is i’m not entirely sure how to match the title to something in a file. This is what I have so far…

    void findBookByTitle(FILE* fp, char title[])
    {
       FILE * fp = fopen(fp, "r");
       while(!EOF && *fp = title){
          printf("Title: <%c> \n", title);
       }
       if(EOF && *fp != title ){
          printf("No books match the title: <%c> ", title);
       }
    }

As well when I compile I get a few errors, it might be pointless to address these as my function remains incomplete but a few of these really confuse me.

34: error: ‘fp’ redeclared as different kind of symbol
32: note: previous definition of ‘fp’ was here
34: warning: passing argument 1 of ‘fopen’ from incompatible pointer type
/usr/include/stdio.h:251: note: expected ‘const char * restrict‘ but argument is of type ‘struct FILE *’
35: error: invalid operands to binary && (have ‘int’ and ‘FILE’)
38: error: invalid operands to binary != (have ‘FILE’ and ‘char *’)

Answer 1

1. Your function is declared as taking a FILE * as its first argument, but it then proceeds to treat that argument as if it’s a filename and try to open another FILE * (with the same name!) using it. Make up your mind on whether the argument is a FILE * or a char *, and change your code accordingly.

2. You are trying to use EOF to test for EOF on fp. It’s not quite that simple. Try feof(fp) instead.

3. You are trying to read from fp using *fp = title (and *fp != title). This doesn’t make any sense at all. You need to use a function to read from the file pointer, such as fgets or fscanf.