How to store an array of values of unknown size in a struct

Question

I currently have this struct that I have created, I have intialised the pointers in main. And I am stuck with the understanding of how to add a value to the pointers then resize it, because it is waiting for user input. The code below is what I in a shortened version, basically I want to know how to add each value of job to the jobNum variable in the struct and resize it so i can store an arbitrary number of values for jobNum. I am quite new to memory allocation.

    typedef struct {
         int* jobNum;
     }JobInfo;

   void get_job(JobInfo* jobCalled, int job){
        jobCalled->jobNum = job;

   }
     void main(int argc, char *argv[]){
         jobCalled.jobNum = malloc(sizeof(int));
    
        while(1){
            //Other Processes
            if (USER_INPUT == 'job'){
                 int job = argv[1];
                 get_job(&jobCalled, job);
           }
        }
    
}

Answer 1

It sounds like you're having trouble understanding allocation. I would suggest learning about linked lists. Basically in a nutshell:

typedef struct{
    void *head;
    void *next;
}myType;

void addElem(myType *ptr){
    myType *new = (myType*)malloc(sizeof(myType));
    ptr->next = new;
    new->next = NULL;
}

This is a barebones way of doing what you're talking about, where the head element points to your first job, but I believe it would suit you to learn about casting, allocation, etc. You will most likely need to create a function that will initialize your head first job as well. You will also likely want to use free to de-allocate memory from the list if you're removing elements. It is also worth noting that it would be better to have a separate type that will be an individual element so that you only allocate one head pointer, but this way is easier if you're having trouble understanding the concept.