C Program to Create Employee Record and Update it

    /*

     * C Program to Create Employee Record and Update it

     */

    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #define size 200

     struct emp
    {

        int id;
        char *name;
    }*emp1, *emp3;

    
    void display();
    void create();
    void update();

    
    FILE *fp, *fp1;
    int count = 0;
    

    void main(int argc, char **argv)

    {
        int i, n, ch;
   

        printf("1] Create a Record\n");
        printf("2] Display Records\n");
        printf("3] Update Records\n");
        printf("4] Exit");
        while (1)

        {
            printf("\nEnter your choice : ");
            scanf("%d", &ch);
            switch (ch)
            {
            case 1:   

                fp = fopen(argv[1], "a");
                create();
                break;

            case 2:   

                fp1 = fopen(argv[1],"rb");
                display();
                break;

            case 3:   

                fp1 = fopen(argv[1], "r+");
                update();
                break;

            case 4:
                exit(0);

            }

        }

    }

    

    /* To create an employee record */

    void create()

    {
        int i;

        char *p;

        emp1 = (struct emp *)malloc(sizeof(struct emp));
        emp1->name = (char *)malloc((size)*(sizeof(char)));
        printf("Enter name of employee : ");
        scanf(" %[^\n]s", emp1->name);
        printf("Enter emp id : ");
        scanf(" %d", &emp1->id);
        fwrite(&emp1->id, sizeof(emp1->id), 1, fp);
        fwrite(emp1->name, size, 1, fp);
        count++;   // count to number of entries of records
        fclose(fp);
    }

    
    /* Display the records in the file */

    void display()

    {   

        emp3=(struct emp *)malloc(1*sizeof(struct emp));   
        emp3->name=(char *)malloc(size*sizeof(char));
        int i = 1;
  

        if (fp1 == NULL)   
            printf("\nFile not opened for reading");
        while (i <= count)

        {
            fread(&emp3->id, sizeof(emp3->id), 1, fp1);
            fread(emp3->name, size, 1, fp1);
            printf("\n%d %s",emp3->id,emp3->name);
            i++;

        }

        fclose(fp1);
        free(emp3->name);
        free(emp3);

    }
   

    void update()

    {
        int id, flag = 0, i = 1;

        char s[size];

      if (fp1 == NULL)

        {
            printf("File cant be opened");
            return;

        }

        printf("Enter employee id to update : ");
        scanf("%d", &id);
        emp3 = (struct emp *)malloc(1*sizeof(struct emp));
            emp3->name=(char *)malloc(size*sizeof(char));
        while(i<=count)

        {   

            fread(&emp3->id, sizeof(emp3->id), 1, fp1);

            fread(emp3->name,size,1,fp1);

            if (id == emp3->id)

            {

                printf("Enter new name of emplyee to update : ");   

                scanf(" %[^\n]s", s);

                fseek(fp1, -204L, SEEK_CUR);

                fwrite(&emp3->id, sizeof(emp3->id), 1, fp1);

                fwrite(s, size, 1, fp1);

                flag = 1;

                break;

            }

            i++;

        }

        if (flag != 1)

        {

            printf("No employee record found");

            flag = 0;

        }

        fclose(fp1);

        free(emp3->name);        /* to free allocated memory */

        free(emp3);

    }