文件编程file_copy.c

//Linux文件编程 — — 系统文件调用中的file_cp.c
//待修改。。。

 1 #include <stdio.h>
 2 #incldue <sys/stat.h>
 3 #include <fcntl.h>
 4 #include <errno.h>
 5 
 6 #define BUFFSIZE 1024
 7 
 8 int main(int argc, char *argv[])
 9 {
10     int from_fd, to_fd;
11     int bytes_read, bytes_write;
12     char buffer[BUFFSIZE];
13     char *ptr;
14 
15     if(argc != 3)
16     {
17         fprintf(stderr, "Usage: %s from_file to_file\n", argv[0]);
18         exit(EXIT_FAILURE); 
19     }
20 
21 //open from_file
22     if((from_fd = open(argv[1], O_RDONLY)) == -1)
23     {
24         fprintf(stderr, "Open %s ERROR:%s\n", argv[1], strerror(errno));
25         exit(EXIT_FAILURE);
26     }
27 //creat to_file
28     if((to_fd = open(argv[2], O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR)) == -1)
29     {
30     　　 fprintf(stderr, "Open %s ERROR:%s", argv[2], strerror(errno));
31　　　    exit(EXIT_FAILURE);
32     }
33 
34 //经典的拷贝文件代码
35     while(bytes_read = read(from_fd, buffer, BUFFSIZE))
36     {
37     if((bytes_read == -1) && (errno != EINTR)) break;
38     else if(bytes_read > 0)
39     {
40         ptr = buffer;
41         while(bytes_write = write(to_file, buffer, bytes_read))
42         {
43          //发生了一个致命的错误
44         if((bytes_write == -1) && (errno != EINTR)) break;
45         //写完了所有读的字节
46         else if(bytes_write == bytes_read) break;
47         //只写了一部分，继续写
48         else if(bytes_write > 0)
49         {
50             ptr += bytes_write;
51             bytes_read -= bytes_write;   
52         }
53         }
54         //写的时候发生了错误
55         if(bytes_write == -1) break;
56     }
57     }
58     close(from_fd);
59     close(to_fd);
60     exit(0);
61 }