CODEWITHSUNDEEP
cfile
user1377492
user1377492

Reputation: 23

c: reading from files

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 *')

Upvotes: 2

Views: 1981

Answers (3)

qwertz
qwertz

Reputation: 14792

  1. You have FILE *pt twice
  2. You can't compare a FILE pointer with a string (char *)
  3. You can't output a string with the option %c
  4. EOF is -1 and with the operator ! this is true if EOF is 0 but EOF will never change
  5. Your algorithm is strange

The right code should be right (so far I've understand your problem):

#include <stdio.h>
#include <string.h>

void findBookTitle(char *path, char **title, int titles) {
    FILE *fp = fopen(path, "r");
    char line[100];
    int i = 0, count = 0;
    while (fgets(line, 100, fp) != NULL) {
        while (i < titles)
            if (!strcmp(title[i], line)) {
                printf("Title: <%s>\n", line);
                count++;
            }
        i = 0;
    }
    if (!count)
        printf("No books found.\n");
}

Upvotes: 0

user149341
user149341

Reputation:

  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.

Upvotes: 4

Paul
Paul

Reputation: 141829

You are overwriting the value in your file pointer with a pointer to a char when you use assignment like that (*fp = title). After that all kinds of problems will happen.

You probably also need to remove the line:

   FILE * fp = fopen(fp, "r");

Since you already have a FILE * fp isn't the name of a file to open. It's an already opened file.

Upvotes: 0

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