// cp <file1> <file2>
// implemented with libc and *zero* error handling

// dd bs=1M count=10 </dev/urandom >random_file
// ./time ./cp_libc_one_byte random_file random_file_copy
// strace ./cp_libc_one_byte random_file random_file_copy
/*
cp
real   0m0.064s
user   0m0.000s
sys    0m0.015s

lib
real   0m8.057s
user   0m0.772s
sys    0m7.221s
*/
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(int argc, char *argv[]) {
    // copy bytes one at a time from  pathname passed as
    // command-line argument 1 to pathname given as argument 2
    int read_file_descriptor = open(argv[1], O_RDONLY);
    int write_file_descriptor = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);
    
    if(read_file_descriptor < 0){
        perror(argv[1]);  
        return 1;
    } 

    if(write_file_descriptor < 0){
        perror(argv[2]);  
        return 1;
    }

    char c;
    ssize_t n_read;
    while( (n_read = read(read_file_descriptor, &c, 1)) > 0 ){
        write(write_file_descriptor, &c, 1);
    }


    // good practice to close file descriptions as soon as finished using them
    // not necessary needed here as program about to exit
    close(read_file_descriptor);
    close(write_file_descriptor);
    return 0;
}