C Programming Code Examples

C > File Operations Code Examples

Compare two Binary Files, Printing the First Byte Position where they Differ

Compare two Binary Files, Printing the First Byte Position where they Differ

    #include <stdio.h>

    void compare_two_binary_files(FILE *,FILE *);

    int main(int argc, char *argv[])

    {

        FILE *fp1, *fp2;

        if (argc < 3)

        {

            printf("\nInsufficient Arguments: \n");

            printf("\nHelp:./executable <filename1> <filename2>\n");

            return;

        }

        else

        {

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

            if (fp1 == NULL)

            {

                printf("\nError in opening file %s", argv[1]);

                return;

            }

            fp2 = fopen(argv[2], "r");

            if (fp2 == NULL)

            {

                printf("\nError in opening file %s", argv[2]);

                return;

            }

            if ((fp1 != NULL) && (fp2 != NULL))

            {

                compare_two_binary_files(fp1, fp2);

            }

        }

    }

    /* compare two binary files character by character     */

    void compare_two_binary_files(FILE *fp1, FILE *fp2)

    {

        char ch1, ch2;

        int flag = 0;

        while (((ch1 = fgetc(fp1)) != EOF) &&((ch2 = fgetc(fp2)) != EOF))

        {

            /* character by character comparision
                 if equal then continue by comparing till the end of files       */

            if (ch1 == ch2)

            {

                flag = 1;

                continue;

            }

            /* If not equal then returns the byte position              */

            else

            {

                fseek(fp1, -1, SEEK_CUR);        

                flag = 0;

                break;

            }

        }

        if (flag == 0)

        {

            printf("Two files are not equal :  byte poistion at which two files differ is %d\n", ftell(fp1)+1);

        }

        else

        {

            printf("Two files are Equal\n ", ftell(fp1)+1);

        }

    }