cp命令的實現

[cpp]
#include <unistd.h>  
#include <fcntl.h>  
#include <stdlib.h>  
 
#define BUFFERSIZE 4096  
#define COPYMODE   0644  
 
void oops(char *, char *); 
 
int main(int argc, char *argv[]) 
{ 
    int in_fd, out_fd, n_chars; 
    char buf[BUFFERSIZE]; 
 
    if (argc != 3) 
    {    
        fprintf(stderr, "Usage: %s source destination\n", *argv); 
        exit(1); 
    }    
 
    if ((in_fd = open(argv[1], O_RDONLY)) == -1) 
        oops("Cannot open ", argv[1]); 
     
    if ((out_fd = creat(argv[2], COPYMODE)) == -1) 
        oops("Cannot creat ", argv[2]); 
     
    while ((n_chars = read(in_fd, buf, BUFFERSIZE)) > 0) 
    {    
        if (write(out_fd, buf, n_chars) != n_chars) 
        {    
            oops("Write error to ", argv[2]); 
        }    
    }    
 
    if (n_chars == -1) 
        oops("Read error from ", argv[1]); 
 
    if (close(in_fd) == -1 || close(out_fd) == -1)   
        oops("Error closing files", ""); 
    return 0; 
} 
void oops(char *s1, char *s2) 
{ 
    fprintf(stderr, "Error: %s", s1); 
    perror(s2); 
    exit(1); 
}