Problem with filling the linked list with strtok

Question

Im having troubles with the next piece of code...

I have defined a linked list struct

    typedef struct node {
        char *cmd;
        char *value; 
        int delay; 
        struct node *next;
    } node_t;

im reading commands from a text file called commands.txt

write:0x02:1
read:0x04:2 
set:0xff:2
reset:0xfa:2

the code below works if i use two buffers (temp and temp1) but if i replace temp1 with temp it does not parse it correctly. it gives me

Tokenized2 read x04 1
Tokenized2 read 0x04 2
Tokenized2 read x04 1
Tokenized2 read 0x04 2

The code is:

    char *filename = "commands.txt";
    FILE *fp = fopen(filename, "r");
    
    node_t *head = (node_t *)malloc(sizeof(node_t));
    node_t *hp = head; 
    char temp[14];
    char temp1[14];
  
    fgets(temp, 14, fp);  
    hp->cmd = strtok(temp, ":");
    hp->value = strtok(0, ":");
    hp->delay = atoi(strtok(0, ":"));
    hp->next = (node_t *)malloc(sizeof(node_t));
    hp = (node_t *)hp->next; Blaz
    
    fgets(temp1, 14, fp);
    hp->cmd = strtok(temp1, ":");
    hp->value = strtok(0, ":");
    hp->delay = atoi(strtok(0, ":"));
    hp->next = NULL; 
    hp = head;

    printf("Tokenized2 %s %s %d\n", hp->cmd, hp->value, hp->delay);
    hp = hp->next;
    printf("Tokenized2 %s %s %d\n", head->next->cmd, head->next->value, head->next->delay);
    printf("Tokenized2 %s %s %d\n", head->cmd, head->value, head->delay);
    printf("Tokenized2 %s %s %d\n", head->next->cmd, head->next->value, head->next->delay);

    fclose(fp);

The bottom printfs are redundant, I was just testing if it works with classic access to head and via pointer. Eventually I would like to make this piece of code work.

    const unsigned MAX_LENGTH = 256;
    char cmdbuffer[MAX_LENGTH];
    node_t *head = (node_t *)malloc(sizeof(node_t));
    node_t *hp = head; 
    while (fgets(cmdbuffer, MAX_LENGTH, fp)) {
        hp->cmd = strtok(cmdbuffer, ":");
        hp->value = strtok(0, ":");
        hp->delay = atoi(strtok(0, ":"));
        hp->next = (node_t *)malloc(sizeof(node_t));
        hp = (node_t *)hp->next;
    }
    hp->next = NULL; 
    printf("Tokenized %s %s %d\n", head->cmd, head->value, head->delay);
    printf("Tokenized2 %s %s %d\n", head->next->cmd, head->next->value, head->next->delay);

How can I solve this problem?

Answer 1

I managed to solve it with strdup. Here is the code ...

FILE *fp = fopen("commands.txt", "r");

    if (fp == NULL){
        printf("Error: could not open text file");
        return 1;
    }

    const unsigned MAX_LENGTH = 256;
    char cmdbuffer[MAX_LENGTH];
    node_t* head = malloc(sizeof(node_t));
    node_t* hp = head; 
    char* sdup; 

    while (fgets(cmdbuffer, MAX_LENGTH, fp)){
        sdup = strdup(cmdbuffer);
        hp->cmd = strtok(sdup, ":");
        hp->value = strtok(0, ":");
        hp->delay = atoi(strtok(0, ":"));
        hp->next = malloc(sizeof(node_t));
        hp = (node_t*) hp->next;
    }
    hp->next = NULL; 


    hp = head; 
    while(hp){
        printf("Tokenized: %s %s %d\n", hp->cmd, hp->value, hp->delay);
        free(hp);
        hp = hp->next;
    }

Comments/corrections are welcome!