assgn4/hw4.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <errno.h>
   4 #include <string.h>
   5 #include <pwd.h>
   6
   7 #include <sys/types.h>
   8 #include <sys/stat.h>
   9
  10 int main(int argc, char *argv[]) {
  11
  12         struct stat    file_stat;
  13         struct passwd *file_pd;
  14
  15         int argc_decr;
  16         mode_t *ft;
  17
  18         extern int errno;
  19
  20         argc_decr = argc; /* K&R 117(§5.10) warns against decrementing argc directly */
  21
  22         if(argc <= 1 || argc >= 5) {
  23
  24                 printf("USAGE: %s <file> [-o, -c]\n", argv[0]);
  25                 return 1;
  26
  27         } else if(stat(argv[1], &file_stat)) {
  28
  29                 if(errno == ENOENT)
  30                         printf("provided file does not exist.\n");
  31                 else if(errno == EACCES)
  32                         printf("improper permissions to read from file.\n");
  33                 else if(errno == ENAMETOOLONG)
  34                         printf("provided path is too long.\n");
  35                 else if(errno == ENOTDIR)
  36                         printf("provided path contains a non-existant directory.\n");
  37                 else if(errno == EOVERFLOW)
  38                         printf("provided file cannot be properly contained into a stat buf.\n");
  39                 else if(errno == ELOOP)
  40                         printf("provided file points to an irresolvable symlink chain.\n");
  41
  42                 return errno;
  43         }
  44
  45         printf("file size in bytes: %llu\n", file_stat.st_size);
  46
  47         while(argc_decr > 2) {
  48
  49                 if(!strncmp(argv[argc_decr - 1], "-o", 5)) {
  50
  51                         if((file_pd = getpwuid(file_stat.st_uid)) != NULL)
  52                                 printf("file owned by user %s.\n", file_pd->pw_name);
  53
  54                         else
  55                                 printf("file owned by uid %d.\n", file_stat.st_uid);
  56
  57                 } else if(!strncmp(argv[argc_decr - 1], "-t", 5)) {
  58
  59                         printf("file is a ");
  60                         ft = &(file_stat.st_mode);
  61
  62                         if     (S_ISBLK(*ft))  printf("block device.\n");
  63                         else if(S_ISCHR(*ft))  printf("character device.\n");
  64                         else if(S_ISFIFO(*ft)) printf("fifo pipe.\n");
  65                         else if(S_ISREG(*ft))  printf("regular file.\n");
  66                         else if(S_ISDIR(*ft))  printf("directory.\n");
  67                         else if(S_ISLNK(*ft))  printf("symbolic link.\n");
  68
  69
  70                 } else {
  71
  72                         printf("provided argument is invalid, must be '-t' or '-o'.\n");
  73                         return 1;
  74                 }
  75
  76                 argc_decr--;
  77         }
  78
  79         return 0;
  80 }