C Programming Code Examples

C > File Operations Code Examples

Create Employee File Name Record that is taken from the Command-Line Argument

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);

        }

    }