How to populate a linked list from a file

Question

I am trying to populate a linked list reading in from a file. I have been attempting to use strtok() to break apart a string using " " as a delimiter. When I call my addEntry() function it is only adding the first letter of each string to a new node. I realize this is probably a simple oversight, so please excuse my ignorance as I am still quite new to coding.

The specific section of code I am having trouble with is:

void readData(struct boggleDataNode **headRef){
    //initializing variables including
    //opening the input file
    int counter = 96;
    int i = 0;
    char dataLine[LENGTH];
    char *data;
    char *fileName = "BoggleData.txt";
    FILE *filePointer;

    printf("Trying to open file %s\n", fileName);
    filePointer = fopen(fileName, "r"); //read mode
    printf("Successfully opened file %s\n", fileName);

    if (filePointer == NULL){
        perror("Error while opening file. \n");
        exit(0);
    }

    //loop until find end of file
    while ( fgets(dataLine, LENGTH, filePointer) != NULL){
        //I feel like i should be using a nested loop here but I can't figure out how to do it 
        printf("dataLine = %s\n", dataLine);
        data = strtok(dataLine, " ");
        printf("data = %s\n", data);
        //fgets(data, 3, filePointer);
        addEntry(headRef, data);
        //nested loop should end here
    }
}

My output is only 16 nodes, the first letter from each line, when it should be 96 nodes long. The file which I am reading from is:

D R L X E I
C P O H S A
N H N L Z R
W T O O T A
I O S S E T
N W E G H E
B O O J A B
U I E N E S
P S A F K F
I U N H M Qu
Y R D V E L
V E H W H R
I O T M U C
T Y E L T R
S T I T Y D
A G A E E N

---

In case the full code is needed:

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

#define LENGTH 80

struct boggleDataNode {
    char data[3];
    struct boggleDataNode *nextData;
};

struct boggleDieSideNode {
    char dieSideData[3];
    struct boggleDieSideNode *nextSide;
};

void readData(struct boggleDataNode **);
void addEntry(struct boggleDataNode **, char *);
void display(struct boggleDataNode *);

int main() {

    int counter = 0;

    struct boggleDataNode * head = NULL;
    struct boggleDieSideNode *head1 = NULL;
    readData(&head);
    display(head);

    system("pause");
    return 0;
}

void readData(struct boggleDataNode **headRef){
    //initializing variables including
    //opening the input file
    int counter = 96;
    int i = 0;
    char dataLine[LENGTH];
    char *data;
    char *fileName = "BoggleData.txt";
    FILE *filePointer;

    printf("Trying to open file %s\n", fileName);
    filePointer = fopen(fileName, "r"); //read mode
    printf("Successfully opened file %s\n", fileName);

    if (filePointer == NULL){
        perror("Error while opening file. \n");
        exit(0);
    }

    //loop until find end of file
    while ( fgets(dataLine, LENGTH, filePointer) != NULL){
        printf("dataLine = %s\n", dataLine);
        data = strtok(dataLine, " ");
        printf("data = %s\n", data);
        //fgets(data, 3, filePointer);
        addEntry(headRef, data);
    }

    fclose(filePointer);

}//cose readData

void addEntry(struct boggleDataNode **headRef, char *data){

    //allocate node
    struct boggleDataNode* temp = (struct boggleDataNode*) malloc(sizeof(struct boggleDataNode));

    //put in data
    strcpy(temp->data, data);

    // link the old list off the new node
    temp->nextData = (*headRef);

    // move the head to point to the new node
    (*headRef) = temp;
}

void display(struct boggleDataNode *headRef){

    struct boggleDataNode *helper = headRef;

    if (helper == NULL){
        return;
    }
    else{
        printf("============================================\n");
        printf("Node #        Data\n");
        printf("============================================\n");

        int counter = 1;

        while (helper != NULL){
            printf("%5d \t %2s\n", counter++, helper->data);
            helper = helper->nextData;
        }
    }
    printf("\n");
    system("pause");
}

Answer 1

You are absolutely correct that you need a nested loop.

strtok needs to be called like this:

for (char *tok = strtok("input", " "); tok; tok = strtok(NULL, " "))
{
    /* use tok */;
}

Answer 2

• if you are only interested in single characters there is no need to read complete lines (and cut them into single characters)
• since you are only interested in single characters, the .data element in the structure does not need to be char data[3]
• a function that reads a file could take the filename as an argument
• and the function could return the list it has read, instead of returning void and passing the result back to the caller via a pointer-to-pointer.

---

#include <stdio.h>
#include <stdlib.h>

struct boggleNode {
    struct boggleNode *next;
    char data;
    };

struct boggleNode * readboggle(char *name);

int main (int argc, char **argv)
{
struct boggleNode *bp;

if (!argv[1]) return 0;

bp = readboggle( argv[1] );

for ( ; bp; bp = bp-> next) {
        printf(" %c", bp->data);
        }

printf("\n" );
return 0;
}

struct boggleNode * readboggle(char *name)
{
struct boggleNode *ret=NULL, **bpp;
FILE *fp;
int ch;

fp = fopen (name, "r" );
if (!fp) return NULL;

ret= NULL;
bpp = &ret;
while(1)        {
        ch = getc(fp);
        if (ch == EOF) break;
        if (ch < 'A' || ch > 'Z') continue;
        *bpp = malloc (sizeof **bpp);
        (*bpp)->data = ch;
        (*bpp)->next = NULL;
        bpp = &(*bpp)->next;
        }
fclose (fp);
return ret;
}