assgn5/copy.c

   1 #include <stdio.h>
   2 #include <fcntl.h>
   3 #include <unistd.h>
   4
   5 #include <sys/stat.h>
   6
   7 int main(int argc, char *argv[]) {
   8
   9         int cur, flag_append, flag_force;
  10         int fd_from, fd_to, mode;
  11         char buf[1];
  12
  13         flag_append = 0;
  14         flag_force  = 0;
  15
  16         while((cur = getopt(argc, argv, "af")) != -1) {
  17                 switch(cur) {
  18
  19                         case 'a':
  20                                 flag_append = 1;
  21                                 break;
  22
  23                         case 'f':
  24                                 flag_force = 1;
  25                                 break;
  26
  27                         default:
  28                                 printf("invalid argument\n");
  29                                 return 1;
  30                 }
  31         }
  32
  33         if(argc - optind != 2) {
  34
  35                 printf("invalid number of args\n");
  36                 return 1;
  37
  38         } else if(flag_append && flag_force) {
  39
  40                 printf("cannot simultaneously specify overwrite and append\n");
  41                 return 1;
  42         }
  43
  44         if(access(argv[optind + 1], F_OK) != -1 && !flag_append && !flag_force) {
  45
  46                 printf("destination file already exists, pass -f to overwrite\n");
  47                 return 1;
  48         }
  49
  50         if(flag_force)       mode = O_TRUNC;
  51         else if(flag_append) mode = O_APPEND;
  52         else                 mode = O_CREAT;
  53
  54         fd_from = open(argv[optind], O_RDONLY);
  55         fd_to   = open(argv[optind + 1], mode | O_WRONLY, S_IRWXU);
  56
  57         if(fd_from == -1) {
  58
  59                 printf("could not open source file\n");
  60                 return 1;
  61
  62         } else if(fd_to == -1 && !flag_force && !flag_append) {
  63
  64                 printf("could not create new destination file\n");
  65                 return 1;
  66
  67         } else if(fd_to == -1) {
  68
  69         }
  70
  71         while(read(fd_from, buf, 1) == 1)
  72                 write(fd_to, buf, 1);
  73
  74         close(fd_from);
  75         close(fd_to);
  76
  77         return 0;
  78 }