so2 lab1 pb1

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <ctype.h>
#include <string.h>

#define BLOCK_SIZE (1 << 12)
#define AUX_SIZE 50

int openFile(const char path[], int flags, mode_t mode) {
    int fd = open(path, flags, mode);
    if (fd < 0) {
        perror("");
        exit(-1);
    }
    return fd;
}

void closeFile(int fd) {
    if (close(fd) == -1) {
        perror("");
        exit(-2);
    }
}

int getLowerCount(int n, const char buff[]) {
    int cnt = 0;
    for (int i = 0; i < n; i++) {
        if (islower(buff[i])) {
            cnt++;
        }
    }
    return cnt;
}

int main(int argc, char *argv[]) {
    if (argc != 3) {
        fprintf(stderr, "Wrong usage!\n");
        exit(-1);
    }
    int fdin = openFile(argv[1], O_RDONLY, 0);
    int fdout = openFile(argv[2], O_WRONLY | O_CREAT | O_TRUNC, S_IRWXU);

    char buff[BLOCK_SIZE];
    int cntLower = 0, readed;
    while ((readed = read(fdin, buff, BLOCK_SIZE)) > 0) {
        cntLower += getLowerCount(readed, buff);
        char aux[AUX_SIZE] = {};
        for (int i = 0; i < readed; i++) {
            if (buff[i] >= 97 && buff[i] <= 122) {
                snprintf(aux, AUX_SIZE, "%c", buff[i]);
            } else {
                snprintf(aux, AUX_SIZE, "(%02X)", buff[i]);
            }
            if (write(fdout, aux, strlen(aux)) == -1) {
                perror("");
                exit(-3);
            }
        }
    }
    if (write(fdout, "\n", 1) == -1) {
        perror("");
        exit(-3);
    }
    {
        char aux[AUX_SIZE];
        snprintf(aux, AUX_SIZE, "Lower letters: %d\n", cntLower);
        if (write(fdout, aux, strlen(aux)) == -1) {
            perror("");
            exit(-3);
        }
    }

    closeFile(fdin);
    closeFile(fdout);
    return 0;
}//dd if=/dev/urandom of=in.txt bs=1000 count=100