• I also present the implementation of list, which emulates the functionality of ls (in particular, ls -lUa).
• The implementation of list and search have many things in common, but the implementation of list is much longer.
• Full implementation of entire list executable is right here.
• Sample output (notice this is my own list, not ls!):

myth7> list /usr/class/cs110/WWW
drwxr-xr-x  8    70296 root       2048 Sep 24 15:07 .
drwxr-xr-x >9 root     root       2048 Sep 25 12:46 ..
drwxr-xr-x  2    70296 root       2048 Sep 24 09:23 restricted
drwx------  2 poohbear operator   2048 Sep 24 09:23 repos
drwx------ >9 poohbear operator   2048 Sep 25 16:29 autumn-2017
-rw-------  1 poohbear operator     89 Sep 24 15:03 index.html

• I don't present the entire implementation. I just show one key function: the one that knows how to print out the permissions information for an arbitrary entry.

Implementation of list's listPermissions:

static inline void updatePermissionsBit(bool flag, char permissions[], size_t column, char ch) {
  if (flag) permissions[column] = ch;
}

static const size_t kNumPermissionColumns = 10;
static const char kPermissionChars[] = {'r', 'w', 'x'};
static const size_t kNumPermissionChars = sizeof(kPermissionChars);
static const mode_t kPermissionFlags[] = {
  S_IRUSR, S_IWUSR, S_IXUSR, // user flags
  S_IRGRP, S_IWGRP, S_IXGRP, // group flags
  S_IROTH, S_IWOTH, S_IXOTH  // everyone (other) flags
};
static const size_t kNumPermissionFlags = sizeof(kPermissionFlags)/sizeof(kPermissionFlags[0]);

static void listPermissions(mode_t mode) {
  char permissions[kNumPermissionColumns + 1];
  memset(permissions, '-', sizeof(permissions));
  permissions[kNumPermissionColumns] = '\0';
  updatePermissionsBit(S_ISDIR(mode), permissions, 0, 'd');
  updatePermissionsBit(S_ISLNK(mode), permissions, 0, 'l');
  for (size_t i = 0; i < kNumPermissionFlags; i++) {
    updatePermissionsBit(mode & kPermissionFlags[i], permissions, i + 1,
                         kPermissionChars[i % kNumPermissionChars]);
  }
  printf("%s ", permissions);
}

• Full implementation of list is in list.c.