Understanding Unix/Linux Programming-cp指令练习

1 #include <stdio.h>
2
3 #include <unistd.h>
4
5 #include <fcntl.h>
6
7 #include <stdlib.h>
8
9
10
11 #define BUFFERSIZE 4096
12
13 #define COPYMODE 0644
14
15
16
17 void oops(char *  , char * ) ;
18
19
20
21 main(int ac , char * av[]){
22
23 int in_fd , out_fd , n_chars ;
24
25 char buf[BUFFERSIZE];
26
27
28
29 if( ac != 3 ){
30
31 fprintf(stderr, "usage:%s source destination\n",  *av );
32
33 exit(1);
34
35 }
36
37
38
39 if( (in_fd = open(av[1] , O_RDONLY)) == -1 ){
40
41 oops("Can not open " , av[1] );
42
43 }
44
45
46
47 if(( out_fd = creat(av[2] , COPYMODE)) == -1 ){
48
49 oops("Can not open " , av[2] );
50
51 }
52
53
54
55 while( (n_chars = read(in_fd , buf , BUFFERSIZE ) ) > 0 ){
56
57
58
59 if( write(out_fd , buf , n_chars) != n_chars )
60
61 {
62
63 oops("Write error to " , av[2]);
64
65 }
66
67 }
68
69
70
71 if(n_chars == -1)
72
73 {
74
75 oops("Read error from " , av[1]);
76
77 }
78
79
80
81 if( close(in_fd ) == -1 || close( out_fd ) == -1 ){
82
83 oops("Error closing files." , "");
84
85 }
86
87
88
89 }
90
91
92
93 void oops(char * s1 , char * s2 ){
94
95 fprintf(stderr, "Error:%s\n", s1 );
96
97 perror(s2);
98
99 exit(1);
100
101 }