Pass String array and indexes using Struct to a thread in C - c

Question

I am trying to pass a string array and indexes from where to start end searching in the array, I am unable to solve it from the last two days. I am sending to the pthread_create a struct data thread_data, here i am able to send the int and long data, but not the string array, can someone help me, how to pass these.
struct data{
int tid;
unsigned long start;
unsigned long end;
char * word;
char * str;
};
struct data thread_data[NUM_THREADS];
void *searchString(void *passeddata)
{
struct data *t_data;
int tid1;
char * str[3];
t_data=(struct data *) passeddata;
tid1=t_data->tid;
str=t_data->str;
.....
pthread_exit(NULL);
}
int main(int argc, char *argv[])
{
...
char work[]={"First Line","Second line","Third line"};
...
while(fgets(arr[index],120, fp)!=NULL){
index=index+1;
thread_data[index].tid=index;
thread_data[index].str=work;
...
rc=pthread_create(&threads[index],NULL,searchString,(void *)&thread_data[index]);
...
}
pthread_exit(NULL);
}

Answer 1

To hold the multiple strings you need 2D array.
const char *work[]={"First Line","Second line","Third line", "Fourth Line"};
You need to use pointer to pointer in struct data to hold the above array.
struct data{
.....
const char **str;
size_t lenOfStr;
};
And pass the length of array explicitly to thread function from main function.
Your sample code may look like below.
#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
struct data{
int tid;
unsigned long start;
unsigned long end;
char * word;
const char **str;
size_t lenOfStr;
};
struct data thread_data[3];
void *searchString(void *passeddata)
{
struct data *t_data;
int tid1;
const char **str = NULL;
t_data=(struct data *) passeddata;
tid1=t_data->tid;
str=t_data->str;
int i = 0;
for (i = 0;i<t_data->lenOfStr;i++)
printf("%s\n", str[i]);
pthread_exit(NULL);
}
int main(int argc, char *argv[])
{
const char *work[]={"First Line","Second line","Third line", "Fourth Line"};
int index = 0;
pthread_t threadid=0;
thread_data[index].tid=index;
thread_data[index].str=work;
thread_data[index].lenOfStr = sizeof(work)/sizeof(*work); // Calculate the size of work here
int rc=pthread_create(&threadid,NULL,searchString,&thread_data[index]);
pthread_exit(NULL);
}