FileHandling23.c

/*
 * C Program to Create Employee File Name Record that is taken from the Command-Line Argument 
 */
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
 
struct emprec
{
    int empid;
    char *name;
};
typedef struct emprec emp;
 
void insert(char *a);
void display(char *a);
void update(char *a);
int count;
void main(int argc, char *argv[])
{
    int choice;    
 
    while (1)
    {
        printf("Enter the choice\n");
        printf("1-Insert a new record into file\n2-Display the records\n");
        printf("3-Update the record\n4-Exit\n");
        scanf("%d",  &choice);
        switch (choice)
        {
        case 1:
            insert(argv[1]);
            break;
        case 2:
            display(argv[1]);
            break;
        case 3:
            update(argv[1]);
            break;
        case 4:
            exit(0);
        default:
            printf("Enter the correct choice\n");
        }
    } 
}
 
/* To insert a new recored into the file */
void insert(char *a)
{
    FILE *fp1;
    emp *temp1 = (emp *)malloc(sizeof(emp));
    temp1->name = (char *)malloc(200 * sizeof(char)); //allocating memory for pointer 
 
    fp1 = fopen(a, "a+");
    if (fp1 == NULL)
        perror("");
    else
    {
        printf("Enter the employee id\n");
        scanf("%d", &temp1->empid);
        fwrite(&temp1->empid, sizeof(int), 1, fp1);
        printf("Enter the employee name\n");
        scanf(" %[^\n]s", temp1->name);
        fwrite(temp1->name, 200, 1, fp1);
        count++;
    }
    fclose(fp1);
    free(temp1);
    free(temp1->name);
}
 
/* To display the records in the file */
void display(char *a)
{
    FILE *fp1;
    char ch;
    int var = count;
    emp *temp = (emp *)malloc(sizeof(emp));
    temp->name = (char *)malloc(200*sizeof(char));
 
    fp1 = fopen(a, "r"); 
    if (count == 0)
    {
        printf("no records to display\n");
        return;
    }
    if (fp1 == NULL)
        perror("");
    else
    {
        while(var)    // display the employee records
        {
            fread(&temp->empid, sizeof(int), 1, fp1);
            printf("%d", temp->empid);
            fread(temp->name, 200, 1, fp1);
            printf(" %s\n", temp->name);
            var--;
        }
    }
    fclose(fp1);
    free(temp);
    free(temp->name);
}
 
/* To Update the given record */
void update(char *a)
{
    FILE *fp1;
    char ch, name[200];
    int var = count, id, c;
    emp *temp = (emp *)malloc(sizeof(emp));
    temp->name = (char *)malloc(200*sizeof(char));
 
    fp1 = fopen(a, "r+");
    if (fp1 == NULL)
        perror("");
    else
    {
        while (var)    //displaying employee records so that user enter correct employee id
        {
            fread(&temp->empid, sizeof(int), 1, fp1);
            printf("%d", temp->empid);
            fread(temp->name, 200, 1, fp1);
            printf(" %s\n", temp->name);
            var--;
        }
        printf("enter which employee id to be updated\n");
        scanf("%d", &id);
        fseek(fp1, 0, 0);
        var = count;
        while(var)    //loop to update the name of entered employeeid
        {
            fread(&temp->empid, sizeof(int), 1, fp1);
            if (id == temp->empid)
            {    
                printf("enter employee name for update:");
                scanf(" %[^\n]s", name);
                c = fwrite(name, 200, 1, fp1);    
                break;    
            }
            fread(temp->name, 200, 1, fp1);
            var--;
        } 
        if (c == 1)
            printf("update of the record succesfully\n");
        else
            printf("update unsuccesful enter correct id\n");
            fclose(fp1);
            free(temp);
            free(temp->name);
    }
}