2.c

/*
Name: Teagan Haddawy
Date: Tuesday Jan 6, 2026
Title: Lab 1 - Part 4
Description: Copies a file using system calls
*/

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

#define BUFFER_SIZE 2048

int main(int argc, char *argv[])
{
        if (argc != 3) //checks for the 3 arguements needed
        {
                fprintf(stderr, "Usage: %s <src_filename> <dst_filename>", argv[0]); //throws error if not given
                exit(1);
        }

        int src_fd = open(argv[1], O_RDONLY); //open the src file using system calls for read only
        if (src_fd < 0)
        {
                perror("error opening file"); //error if opening fails
                exit(1);
        }

        int dst_fd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644 ); //open destination file with write only permissions
        if (dst_fd < 0)
        {
                perror("error opening destination file"); //error if cannot be opened
                exit(1);
        }

        char *buf = malloc(BUFFER_SIZE); //allocated memory for buffer
        if (buf == NULL) //error if memory allocation failed
        {
                perror("Memory allocation failed");
                close(src_fd);
                close(dst_fd);
                exit(1);
        }

        ssize_t bytes_read;
        while ((bytes_read = read(src_fd, buf, BUFFER_SIZE)) > 0) //read the bits from the source file
        {
                write(dst_fd, buf, bytes_read); //write it to the destination file
        }

        free(buf); //free memory
        close(src_fd);
        close(dst_fd);

        printf("File copied using System Calls\n");
        return 0;
}