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Getting an infinite loop trying to read a text file by tokenizing the string in C – Artificial Intelligence

I am trying to read a text file line by line and tokenize them into elements of a struck using custom function. Yet I get an infinite loop trying to do so. My code is as follows: 

typedef struct
{
   char barcodeNumber[5];
   char title[50]; char author[30];
   char publisherCompany[30];
   int publishingYear;
   char isbn[13];
} Book;

Book booklist[100];

void readBooks()
{
    int i = 0;
    char line[255];

    printf("asd");
    FILE *libraryPtr;

    libraryPtr = fopen("books.txt", "r");
    if (libraryPtr == NULL)
        printf("File not found.n");
    else
    {
        while (fgets(line, sizeof(line), libraryPtr) != NULL)
        {

            booklist[i].barcodeNumber = strtok(line, ";");
            booklist[i].title = strtok(NULL, ";");
            booklist[i].author = strtok(NULL, ";");
            booklist[i].publisherCompany = strtok(NULL, ";");
            booklist[i].publishingYear = strtok(NULL, ";");
            booklist[i].isbn = strtok(NULL, ";");
            i++;
        }
    }
    fclose(libraryPtr);
    printf("%s", booklist[1].barcodeNumber);
}

My input file is (Books.txt):

A1234;Elements of Theory of Computation;Harry R. Lewis;Prentice Hall;1998;2132457198219
A1987;Knowledge Acquisiton;Karen L. McGraw;Prentice Hall;1989;1945868279220
M3158;Artificial Intelligence;Patrick H. Winston;Addison Wesley;1992;3243568791940
C8287;Linux Sistem Yonetimi;Tom Adelstein;O'Reilly;2007;1718295464178
E6097;CRYPTOGRAPHY AND NETWORK SECURITY PRINCIPLES;William Stallings;Prentice Hall;2007;9780136097044
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2

Answers


  1. 0

    Strings in C are not like in some high level language, you cannot somply assign strings with the = operator. A complete explanation is beyond the scope of this answer.

    You need this inside your while loop (minumum code, no error checking and/or bounds checking done here).

       strcpy(booklist[i].barcodeNumber, strtok(line, ";"));
   strcpy(booklist[i].title, strtok(NULL, ";"));
   strcpy(booklist[i].author, strtok(NULL, ";"));
   strcpy(booklist[i].publisherCompany, strtok(NULL, ";"));
   char *pyear = strtok(NULL, ";");
   booklist[i].publishingYear = atol(pyear);
   strcpy(booklist[i].isbn, strtok(NULL, ";"));
   i++;

    Id didn’t test the code, but it should at least give you an idea.

    For atol you also need to include:

    #include <stdlib.h>

    EDIT: 

    char barcodeNumber[5];

    should be

    char barcodeNumber[6];

    You need space for the terminating zero.

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  2. 0

    Try this code fragment replacing some of your function code. The errors were due trying to write the strok pointer to a string, instead of copying the string. Apart from being the wrong type, the string pointers became invalid once you moved on to the next line. I also tweaked the way you did the year integer field, and limited the string lengths and the array size i too.

    char *ptr;
Book *bookptr;
while (fgets(line, sizeof(line), libraryPtr) != NULL && i < 100) {
    bookptr = &booklist[i];

    ptr = strtok(line, ";");
    if (ptr)
        strncpy (bookptr->barcodeNumber, ptr, sizeof(bookptr->barcodeNumber)-1);

    // etc...

    ptr = strtok(NULL, ";");
    if (ptr)
        bookptr->publishingYear = atoi (ptr);

    // etc...
    i++;
}
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