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
",  *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
", s1 );
 96 
 97 perror(s2);
 98 
 99 exit(1);
100 
101 }
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