problem in link list C

[shivi_php]

this is my struct

struct student{


    char studentFirstName[40];
    char studentLastName[40];
    int studentAge;
    int studentRollNo;
    char studentClassSection[2];
    int studentTotalNumber;
    char studentPromotion[5];
    struct student* nextPoint;
};

and here is my simple function that i use to insert data into link list but when i do in this way

void insertDataIntolinkList(char*stufirstname,char*stulastname,int stuage,int sturollno,char*stuclasssection,int stutotalnumber,char*stupromotion){
    struct student* tempStudentInfo =(struct student*)malloc(sizeof(student));
    (*tempStudentInfo).studentFirstName = stufirstname;
}

(*tempStudentInfo).studentFirstName = stufirstname; here give me an errore expression must be a modifiable lvalue

[jimblumberg]

You can't use assignment with C-strings, you need to use strcpy().


Jim

[nonpuz]

When I have a large struct like that, that takes a lot of parameters in its constructor (for lack of a better word) I tend to use the struct itself as an argument, this also makes expanding the structure easier as you don't have to remember to add the new parameter to your prototypes and the definition of the function.

Example:

struct student{
    char studentFirstName[40];
    char studentLastName[40];
    int studentAge;
    int studentRollNo;
    char studentClassSection[2];
    int studentTotalNumber;
    char studentPromotion[5];
    struct student* nextPoint;
};

struct student * new_student(struct student * opt) /* <-- structure itself is the argument list */
{
    struct student * ns;

    if (ns = malloc(sizeof *ns)) {
        strncpy(ns->studentFirstName, opt->studentFirstName, sizeof ns->studentFirstName);
        /* and so on ... */
    }

    return ns;
}

int main(void)
{
    struct student opt = {
        .studentFirstName = "Whatever",
        /* ... */
    };
    struct student * node;


    node = new_student(&opt);
    
    /* ... error check and do stuff with node ... */

    return 0;
}

Now if I add or remove items from the struct student object I don't have to change my parameter list. One other HUGE benefit of this is you can now also use this function to COPY an existing struct student. Simply pass the existing struct you want to copy as the argument to new_student() and you will get a copy of that student in return.

[shivi_php]

if i do in this way where is my mistake thanks very much

this is my global struct pointer
struct student* tempNextPoint = NULL;

i create this function to insert data into link list

void insertDataIntolinkList(char *stufirstname,char *stulastname,int stuage, int sturollno, char *stuclasssection, int stutotalnumber, char *stupromotion){
    struct student* tempStudentInfo = (struct student*)malloc(sizeof(student));
    
    strcpy((*tempStudentInfo).studentFirstName,stufirstname);
    strcpy((*tempStudentInfo).studentLastName,stulastname);
    (*tempStudentInfo).studentAge = stuage;
    (*tempStudentInfo).studentRollNo = sturollno;
    strcpy((*tempStudentInfo).studentClassSection,stuclasssection);
    (*tempStudentInfo).studentTotalNumber = stutotalnumber;
    strcpy((*tempStudentInfo).studentPromotion,stupromotion);


    (*tempStudentInfo).nextPoint = tempNextPoint;
    tempNextPoint = tempStudentInfo;
}

and with this function i display all data but in output ity give me all the same data for all student in link list why ?

void displayAllStudentResult(){
    struct student* tempPrintPoint = tempNextPoint;
    while(tempPrintPoint != NULL){
        printf("\t\t\n student first name is %s ",(*tempPrintPoint).studentFirstName);
        printf("\t\t\n student last name is %s ",(*tempPrintPoint).studentLastName);
        printf("\t\t\n student age is %d ",(*tempPrintPoint).studentAge);
        printf("\t\t\n student roll number is %d ",(*tempPrintPoint).studentRollNo);
        printf("\t\t\n student class section is %c ",(*tempPrintPoint).studentClassSection);
        printf("\t\t\n student total number %d ",(*tempPrintPoint).studentTotalNumber);
        printf("\t\t\n student promotion %s ",(*tempPrintPoint).studentPromotion);


        tempPrintPoint = (*tempPrintPoint).nextPoint;
    }


    printf("\n");
}

and in my main i do this way

int studentNumber,num;
    struct student *getStudentInfo;


    getStudentInfo = (struct student*)malloc(sizeof(struct student));


    printf("\t\t\n for how many student you want do this opration -> ");
    scanf("%d",&studentNumber);


    for(num = 1; num <= studentNumber; num++ ){


    printf("\t\t\n enter student firstname (max 40 charecters ) ");
    scanf("%s",&(getStudentInfo)->studentFirstName);


    printf("\t\t\n enter student lastname (max 40 charecters ) ");
    scanf("%s",&(getStudentInfo)->studentLastName);


    printf("\t\t\n enter student age ");
    scanf("%d",&(getStudentInfo)->studentAge);


    printf("\t\t\n enter student roll number ");
    scanf("%d",&(getStudentInfo)->studentRollNo);


    printf("\t\t\n enter student class section (A,B,C,D ecc... ) ");
    scanf("%s",&(getStudentInfo)->studentClassSection);


    printf("\t\t\n enter student total number ");
    scanf("%d",&(getStudentInfo)->studentTotalNumber);


    printf("\t\t\n enter student promotion result  (pass or fail) ");
    scanf("%s",&(getStudentInfo)->studentPromotion);


    }


    insertDataIntolinkList((*getStudentInfo).studentFirstName,(*getStudentInfo).studentLastName,(*getStudentInfo).studentAge,(*getStudentInfo).studentRollNo,(*getStudentInfo).studentClassSection,(*getStudentInfo).studentTotalNumber,(*getStudentInfo).studentPromotion);


    for(num=0;num<=studentNumber;num++){
        displayAllStudentResult();
    }


    free(getStudentInfo);