OS 6

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <dirent.h>
#include <sys/stat.h>
#include <string.h>
#include <time.h>

#define MAXSTRLENGTH 50

void getFilePath(char *dirPath, char *fileName, char **buf) {
    memset(*buf, 0, MAXSTRLENGTH * sizeof(char));
    strcat(*buf, dirPath);
    if ((*buf)[strlen(*buf) - 1] != '/') {
        (*buf)[strlen(*buf)] = '/';
    }
    strcat(*buf, fileName);
}

void printFileInfo(char *filePath, struct stat fileStat, FILE *stream) {
    char fileMode[10] = "----------";
    if (fileStat.st_mode & S_IRUSR) fileMode[1] = 'r';
    if (fileStat.st_mode & S_IWUSR) fileMode[2] = 'w';
    if (fileStat.st_mode & S_IXUSR) fileMode[3] = 'x';
    if (fileStat.st_mode & S_IRGRP) fileMode[4] = 'r';
    if (fileStat.st_mode & S_IWGRP) fileMode[5] = 'w';
    if (fileStat.st_mode & S_IXGRP) fileMode[6] = 'x';
    if (fileStat.st_mode & S_IROTH) fileMode[7] = 'r';
    if (fileStat.st_mode & S_IWOTH) fileMode[8] = 'w';
    if (fileStat.st_mode & S_IXOTH) fileMode[9] = 'x';
    fprintf(stream, "File path: %s\nSize: %d bytes\nCreation date: %sIndex descriptor: %d\nFile permissions: %s\n",
    filePath, fileStat.st_size, ctime(&fileStat.st_ctime), fileStat.st_ino, fileMode);
}

void printInfo(char *filePath1, struct stat fileStat1, char *filePath2, struct stat fileStat2, FILE *stream) {
    printFileInfo(filePath1, fileStat1, stream);
    fprintf(stream, "\n");
    printFileInfo(filePath2, fileStat2, stream);
    fprintf(stream, "------------\n");
}

void searchFileInDir2(char *filePath1, struct stat fileStat1, char *dirPath, FILE *fout) {
    struct dirent *file2;
    struct stat fileStat2;
    DIR *dir = opendir(dirPath);
    char *filePath2 = malloc(MAXSTRLENGTH * sizeof(char));
    while ((file2 = readdir(dir)) != NULL) {
        getFilePath(dirPath, file2->d_name, &filePath2);
        stat(filePath2, &fileStat2);
        if (S_ISDIR(fileStat2.st_mode) && strcmp(file2->d_name, ".") && strcmp(file2->d_name, "..")) {
            searchFileInDir2(filePath1, fileStat1, filePath2, fout);
        }
        else if (S_ISREG(fileStat2.st_mode) && fileStat1.st_size == fileStat2.st_size && strcmp(filePath2, filePath1)) {
            FILE *f1 = fopen(filePath1, "r");
            FILE *f2 = fopen(filePath2, "r");
            int temp = 0;
            bool isIdentical = true;
            while (isIdentical && temp != EOF) {
                isIdentical = (temp = fgetc(f1)) == fgetc(f2);
            }
            fclose(f1);
            fclose(f2);
            if (isIdentical) {
                printInfo(filePath1, fileStat1, filePath2, fileStat2, stdout);
                printInfo(filePath1, fileStat1, filePath2, fileStat2, fout);
            }
        }
    }
    free(filePath2);
    closedir(dir);
}

void searchIdenticalFiles(char *dirPath1, char *dirPath2, FILE *fout) {
    struct dirent *file;
    struct stat fileStat;
    DIR *dir1 = opendir(dirPath1);
    char *filePath = malloc(MAXSTRLENGTH * sizeof(char));
    while ((file = readdir(dir1)) != NULL) {
        getFilePath(dirPath1, file->d_name, &filePath);
        stat(filePath, &fileStat);
        if (S_ISDIR(fileStat.st_mode) && strcmp(file->d_name, ".") && strcmp(file->d_name, "..")) {
            searchIdenticalFiles(filePath, dirPath2, fout);
        }
        else if (S_ISREG(fileStat.st_mode)) {
            searchFileInDir2(filePath, fileStat, dirPath2, fout);
        }
    }
    free(filePath);
    closedir(dir1);
}

int main(int argc, char *argv[]) {
    if (argc != 4) {
        printf("Incorrect number of arguments.\n");
        return 1;
    }
    FILE *fout = fopen(argv[3], "w");
    searchIdenticalFiles(argv[1], argv[2], fout);
    fclose(fout);
    return 0;
}