merge_files.c

//program to merge two files

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

struct record
{
    char name[20];
    int roll;
    int marks;
} stu1, stu2;

int main(void)
{
    FILE *fp1, *fp2, *fp3;
    int i, j;
    if ((fp1 = fopen("SelectionA", "rb")) == NULL)
    {
        printf("Error in openning file..\n");
        exit(1);
    }
    if ((fp2 = fopen("SelectionB", "rb")) == NULL)
    {
        printf("Error in openning file..\n");
        exit(1);
    }
    if ((fp3 = fopen("merged", "wb")) == NULL)
    {
        printf("Error in openning file..\n");
        exit(1);
    }
    i = fread(&stu1, sizeof(stu1), 1, fp1);
    j = fread(&stu2, sizeof(stu2), 1, fp2);

    while ((i == 1) && (j == 1))
    {
        if (stu1.marks > stu2.marks)
        {
            fwrite(&stu1, sizeof(stu1), 1, fp3);
            i = fread(&stu1, sizeof(stu1), 1, fp1);
        }
        else
        {
            fwrite(&stu2, sizeof(stu2), 1, fp3);
            j = fread(&stu2, sizeof(stu2), 1, fp2);
        }
    }
    while (i == 1)
    {
        fwrite(&stu1, sizeof(stu1), 1, fp3);
        i = fread(&stu2, sizeof(stu2), 1, fp1);
    }
    while (j == 1)
    {
        fwrite(&stu1, sizeof(stu1), 1, fp3);
        j = fread(&stu2, sizeof(stu2), 1, fp2);
    }
    fclose(fp1);
    fclose(fp2);
    fclose(fp3);
    return 0;
}