I have written a code to enter the name, age, department id, company name, and salary respectively, of employees from a text file into a linked list. Right now, In my code, I have created an insert function and a display function. When I ran the code on the command prompt there were no errors found. However, my list did not get printed. Can someone help me out with this if possible? thankyou.

Here are the details of the file, it is called employee.txt:

Peter 30 1001 Apple 8000
Joseph 50 1002 Oracle 4000
Mary 40 1003 Samsung 6000
Lilly 40 1203 Samsung 7000
Tony 50 1002 Oracle 3000
Jake 30 1005 Apple 3000
Sam 40 1007 Samsung 4000
Lisa 30 1300 Oracle 5000
Kate 50 1200 Apple 6000
Rick 50 1313 Apple 4000

My Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct personTag {
    char name[20];
    int age;
};

struct officialTag {
    int deptId;
    char cmpName[20];
    double salary;
};

struct employeeTag {
    struct personTag personalInfo;
    struct officialTag officialInfo;
    struct employeeTag *next;
};

typedef struct employeeTag EmpTag;
typedef EmpTag *EmpTagPtr;

void insert(EmpTagPtr *s, char E_name[], int E_age, int E_deptid,
            char E_cmpname[], double E_salary);

void displayEmployees(EmpTagPtr s);

int main() {
    EmpTagPtr start = NULL;

    char E_name[20];
    int E_age;
    int E_deptid;
    char E_cmpname[20];
    double E_salary;

    // reading employee.txt file
    FILE *fp;
    fp = fopen("employee.txt", "r");

    fscanf(fp, "%s,%d,%d,%s,%lf", E_name, &E_age, &E_deptid, E_cmpname,
           &E_salary);

    while (!feof(fp)) {
        insert(&start, E_name, E_age, E_deptid, E_cmpname,
               E_salary);  // inserting data to the new node
        fscanf(fp, "%s,%d,%d,%s,%lf", E_name, &E_age, &E_deptid, E_cmpname,
               &E_salary);
    }

    fclose(fp);

    displayEmployees(start);

    return 0;
}

void insert(EmpTagPtr *s, char E_name[], int E_age, int E_deptid,
            char E_cmpname[], double E_salary) {
    EmpTagPtr current = *s;
    EmpTagPtr prev = NULL;

    // create an empty node
    EmpTagPtr newNode;
    newNode = (EmpTag *)malloc(sizeof(EmpTag));

    // filling in the values
    strcpy(newNode->personalInfo.name, E_name);
    newNode->personalInfo.age = E_age;

    newNode->officialInfo.deptId = E_deptid;
    strcpy(newNode->officialInfo.cmpName, E_cmpname);
    newNode->officialInfo.salary = E_salary;

    newNode->next = NULL;

    while (current != NULL &&
           strcmp(current->personalInfo.name, prev->personalInfo.name) > 0) {
        prev = current;
        current = current->next;
    }

    if (prev == NULL) {
        // add as the first node
        newNode->next = *s;
        *s = newNode;
    } else {
        prev->next = newNode;
        newNode->next = current;
    }
}

void displayEmployees(EmpTagPtr s) {
    EmpTagPtr current = s;

    while (current != NULL) {
        // printing the data part
        printf("Employee name:    %s\n", current->personalInfo.name);
        printf("Company name:     %s\n", current->officialInfo.cmpName);
        printf("Employee Age:     %d\n", current->personalInfo.age);
        printf("Department ID:    %d\n", current->officialInfo.deptId);
        printf("Employee Salary:  %lf\n", current->officialInfo.salary);
        printf("---------------------------------------------------------");
        current = current->next;  // move foward the current pointer
    }

    printf("NULL\n");
}

CodePudding user response：

Your loop to read uses the wrong fscanf format. The loop is also a bit overcomplicated. Just fscanf and check that you successfully extracted the 5 elements. Note the limits for the strings and removed commas:

while (fscanf(fp, "s %d %d s %lf", E_name, &E_age, &E_deptid,
              E_cmpname, &E_salary) == 5)
{
    insert(&start, E_name, E_age, E_deptid, E_cmpname, E_salary);
}

The insert function has a buggy loop to find the insertion point. prev will be a NULL pointer here:

while(current != NULL && strcmp(current->personalInfo.name,
      prev->personalInfo.name) >0 )
{
    prev = current;
    current = current->next;
}

Suggested fix:

void insert(EmpTagPtr *s, char E_name[], int E_age, int E_deptid,
            char E_cmpname[], double E_salary) 
{
    // create an empty node
    EmpTagPtr newNode = malloc(sizeof *newNode);

    // filling in the values
    strcpy(newNode->personalInfo.name, E_name);
    newNode->personalInfo.age = E_age;

    newNode->officialInfo.deptId = E_deptid;
    strcpy(newNode->officialInfo.cmpName, E_cmpname);
    newNode->officialInfo.salary = E_salary;

    // use `newNode` in the comparison:
    while (*s && strcmp(newNode->personalInfo.name,
                        (*s)->personalInfo.name) > 0)
    {
        s = &(*s)->next;
    }

    // `s` now points at the `EmpTagPtr` pointer where the new node should
    // be inserted for the list to be sorted in alphabetical order.
    // If it's the first node to be inserted, `s` points at `start` so
    // you do not need `prev` or `current`:
    newNode->next = *s;
    *s = newNode;
}

Where, person.txt is (an example),

1 Peter 30
2 Joseph 50
3 Mary 40

works.txt

1 1001 8000
2 1002 4000
3 1002 6000

department.txt

1001 1
1002 1

company.txt

1 Apple

Instead of duplicating data, this reduces data redundancy. This is good for if you want to add or make changes to your database. It also mirrors the usage (somewhat) in your programme.