cp命令的实现

#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);

}