Watching for Directory Changes using std::filesystem

1#include <windows.h>
2
3#include <iostream>
4
5void watch_directory(
6  const std::wstring &directory) {
7  HANDLE dir_handle = CreateFileW(
8    directory.c_str(),
9    FILE_LIST_DIRECTORY,
10    FILE_SHARE_READ | FILE_SHARE_WRITE
11      | FILE_SHARE_DELETE,
12    nullptr,
13    OPEN_EXISTING,
14    FILE_FLAG_BACKUP_SEMANTICS,
15    nullptr)
16    ;
17
18  if (dir_handle == INVALID_HANDLE_VALUE) {
19    std::cerr << "Failed to open directory\n";
20    return;
21  }
22
23  char buffer[1024];
24  DWORD bytes_returned;
25
26  while (true) {
27    if (ReadDirectoryChangesW(
28      dir_handle, buffer, sizeof(buffer), TRUE,
29      FILE_NOTIFY_CHANGE_FILE_NAME
30      | FILE_NOTIFY_CHANGE_DIR_NAME
31      | FILE_NOTIFY_CHANGE_ATTRIBUTES
32      | FILE_NOTIFY_CHANGE_SIZE
33      | FILE_NOTIFY_CHANGE_LAST_WRITE
34      | FILE_NOTIFY_CHANGE_LAST_ACCESS
35      | FILE_NOTIFY_CHANGE_CREATION
36      | FILE_NOTIFY_CHANGE_SECURITY,
37      &bytes_returned,
38      nullptr,
39      nullptr
40    )) {
41      FILE_NOTIFY_INFORMATION *info =
42        reinterpret_cast<
43          FILE_NOTIFY_INFORMATION *>(buffer);
44      std::wcout << "Change detected in: "
45        << info->FileName << '\n';
46    } else {
47      std::cerr
48        << "Failed to read directory changes\n";
49    }
50  }
51
52  CloseHandle(dir_handle);
53}
54
55int main() {
56  watch_directory(L"c:\\test");  
57}

1#include <limits.h>
2#include <sys/inotify.h>
3#include <unistd.h>
4
5#include <iostream>
6
7void watch_directory(const std::string &directory) {
8  int inotify_fd = inotify_init();
9  if (inotify_fd < 0) {
10    std::cerr << "Failed to initialize inotify\n";
11    return;
12  }
13
14  int watch_fd = inotify_add_watch(
15    inotify_fd, directory.c_str(),
16    IN_MODIFY | IN_CREATE | IN_DELETE
17  );
18
19  if (watch_fd < 0) {
20    std::cerr << "Failed to add watch\n";
21    close(inotify_fd);
22    return;
23  }
24
25  char buffer[
26    sizeof(struct inotify_event) + NAME_MAX + 1];
27
28  while (true) {
29    int length = read(
30      inotify_fd, buffer, sizeof(buffer));
31    if (length < 0) {
32      std::cerr << "Failed to read inotify events\n";
33      break;
34    }
35
36    struct inotify_event *event = reinterpret_cast<
37      struct inotify_event *>(buffer);
38    if (event->len) {
39      std::cout << "Change detected in: "
40        << event->name << '\n';
41    }
42  }
43
44  inotify_rm_watch(inotify_fd, watch_fd);
45  close(inotify_fd);
46}
47
48int main() {
49  watch_directory("/tmp/test");
50}