Modifying a pthread program to read multiple lines

hello everyone :)

I have a problem with a code I have tried. The code I have tried. The code's objective is this. Read the 3 categories of text from a text file (test.txt) by using 3 separate threads and display them on the terminal.

Amber
John
Damien
Paul
Kyle
sydney
melbourne
canberra
perth
darwin
20
23
21
32
24

The program I wrote reads a string like this,


12345ABCDE!@#$%


So I need some help modifying this program to achieve the above.
It would mean a lot if someone could help me solve this problem as this is the best solution I could come up with.
Thank you for any help.

Output I am trying to get...
Amber from Sydney. Age: 20
John from Melbourne. Age: 23
Damien from Canberra. Age: 21
Paul from Perth. Age: 32
Kyle from Darwin. Age: 24

Code:

---


#include <stdio.h>
#include <pthread.h>
 
 
#define LENGTH 5
 
pthread_mutex_t lock;
 
pthread_t t[3];
 
 
struct tcontainer
{


        // the filename
        const char* name;


        // what are we reading
        int offset;


        // buffers
        char nums[LENGTH];
        char alphas[LENGTH];
        char syms[LENGTH];
};


typedef struct tcontainer container;
 
// the thread
 
void* reader_threadf(void* cont_p)
{
 
    FILE *fp ;
 
    container* co=(container*)cont_p;
 
    char *data_o;
 
    int offset;
 
    // protect offset
 
    pthread_mutex_lock(&lock);
 
    offset=co->offset;
    co->offset++;
 
    pthread_mutex_unlock(&lock);
 
    //open the file
 
    fp=fopen(co->name, "r");
 
    //determine which buffer extract into
 
    if (offset==2)data_o=co->syms; else {if (offset==1)data_o=co->alphas; else data_o=co->nums;}
 
    // move the seek to the position determined by offset
    fseek( fp, LENGTH*offset, SEEK_SET );
 
    // reads the data from the offset
 
    int i=0;
 
    while(i<LENGTH)
    {
        data_o[i]=fgetc(fp);
        i++;     
    }
 
 
    fclose(fp);
 
    return NULL;
 
}
 
 
int main()
 
 
{
 
    container co;
 
    co.offset=0;
    co.name="test.txt";
 
    // launch threads
 
    for (int i=0;i<3;i++)
        pthread_create(&(t[i]), NULL, &reader_threadf, (void*)&co);
 
 
    // finish threads
    for (int i=0;i<3;i++)
        pthread_join(t[i],NULL);
 
 
    // output data
 
    for (int i=0;i<LENGTH;i++)
    {
        printf("%c",co.nums[i]);
        printf("%c",co.alphas[i]);
        printf("%c\n",co.syms[i]);
    }
 
    return 0;
 
 
}

---

I have to use getline instead (instead of the getc), and redo the container buffers into [LENGTH][MAXNAMESIZE] or something like that. And the seek has to adjusted to the proper position. These are the stuff I need help with.

I would suggest you start by making this work.

Code:

---

    reader_threadf((void*)&co);
    reader_threadf((void*)&co);
    reader_threadf((void*)&co);

    for (int i=0;i<LENGTH;i++)
    {
        printf("%c",co.nums[i]);
        printf("%c",co.alphas[i]);
        printf("%c\n",co.syms[i]);
    }

---

For starters, your mutex is wrong because you're assuming that the first thread you spawn would get to the mutex first.
This isn't guaranteed.