more on struct.

how to print struct from another function?
let's say I have code this way

Code:

---

struct student{
int id // simple example
};
main(){
modify_data(); // calls the function.
}
lode_struct_function()
{
// here I load the struct value from the file.
struct student line[i] // i comes from another function.
line[i].id = student_id;
}
modify_data()
{
struct student line[i]  // ? ?????
printf("%d",line[i].id); // here is the key how can i print line[i].id on this function?
}

---

Make use of a pointer, e.g.,

Code:

---

#include <stdio.h>

struct student
{
    int id;
};

void modify_data(struct student *the_student)
{
    the_student->id = 1;
}

int main(void)
{
    struct student a_student = {0};
    modify_data(&a_student);
    /* print the struct, etc */
    return 0;
}

---

Thanks. But I have another function witch loads the struct value from the line of text file.

Code:

---

int load_struct()                                        //this function loads structs element from the file.{
    int x=0;
    int i=count(x);
    struct student line[i];
    char file_line[100];
    char* line_parts;
   
    FILE * fp;                                                          // file opens here.
    if ((fp = fopen ("file.txt", "r")) != NULL)
    {
        while (x<i) {
            fgets(file_line,100,fp);    // gets line from the file.
           
           
            line_parts = strtok(file_line,",");
            line[x].st_id  = atoi(line_parts);
           
           
            line_parts = strtok(NULL, ",");
            strcpy(line[x].st_name,line_parts);
           
            line_parts = strtok(NULL, ",");
            line[x].st_age = atoi(line_parts);
           
            line_parts = strtok(NULL, ",");
            strcpy(line[x].st_dep,line_parts);
           
            line_parts = strtok(NULL, ",");
            line[x].st_grade = atoi(line_parts);
            x++;
           
        }
       
       
    }
    fclose(fp);


    return  0;
}

---

Now I have to use these value in modify_data function. I only call load_struct and modify_data function in the main?
Sorry I am new and not doing much in the pointer. Thanks again.

Notice that you store the data of the file in an array of structs, which is locally declared, thus will go out of scope when the function terminates.

I think an example like this is what you need to get you boosted. :)

SO, if I declare this line as a global variable does that work?
struct student line[i];
this way.

Code:

---

struct student{
  int id;
}line[i]; // to do this way i am getting complain about [i].

---

Are you wanting the function to fill in the whole array, or just one single item/struct/object in that array?

In either case the array should exist in the calling function, not the called function, and certainly not globally; and you should pass the relevant thing into your function. (If you just want to fill in a single object, you would maybe need to pass-by-address so that the contents can be modified.)

Quote:

---

Originally Posted by tabstop

Are you wanting the function to fill in the whole array, or just one single item/struct/object in that array?

In either case the array should exist in the calling function, not the called function, and certainly not globally; and you should pass the relevant thing into your function. (If you just want to fill in a single object, you would maybe need to pass-by-address so that the contents can be modified.)

---

Yikes. I know it's probably a typo or simplification but there is no such thing as "pass-by-address" in C. I'd modify the statement to read "If you just want to fill in a single object, you would maybe need to a pointer to the object so that the contents can be modified."

Quote:

---

Originally Posted by SirPrattlepod

Yikes. I know it's probably a typo or simplification but there is no such thing as "pass-by-address" in C. I'd modify the statement to read "If you just want to fill in a single object, you would maybe need to a pointer to the object so that the contents can be modified."

---

"Pass the address"? "Pass-by-pointer"? You can pick whichever you like. (I think "pass-by-pointer" is probably most common, though? And the CS people probably like "pass by reference", although then you can get into an argument with the C++ people.)

Quote:

---

Originally Posted by tabstop

"Pass the address"? "Pass-by-pointer"? You can pick whichever you like. (I think "pass-by-pointer" is probably most common, though? And the CS people probably like "pass by reference", although then you can get into an argument with the C++ people.)

---

But in C everything is pass-by-value.

Thanks all for your valuable suggestion, Now I'm getting little higher in the pointer. Can you please, suggest me for my illusion about the pointer?
lets say, I have function called fn1(), fn2() and fn3(). I need to do this.

Code:

---

fn1()
{
fn2() // simply i call fn2() here
fn3(*fn2()) // is that it pass by reference ?????
}
fn2()
{
//something and something
}
fn3(what i put here?)
{
//something or manything
}

---

is that possible to do ?