The 17th session in eglug's system programming course, I only attend the session, the slides are not written by me

8. int inotifyd_main(int argc UNUSED_PARAM, char **argv) { unsigned mask = IN_ALL_EVENTS; // assume we want all events struct pollfd pfd; char **watched = ++argv; // watched name list const char *args[] = { *argv, NULL, NULL, NULL, NULL }; // open inotify pfd.fd = inotify_init(); if (pfd.fd < 0) bb_perror_msg_and_die(&quot;no kernel support&quot;); // setup watched while (*++argv) { char *path = *argv; char *masks = strchr(path, ':'); int wd; // watch descriptor // if mask is specified -> if (masks) { *masks = ''; // split path and mask // convert mask names to mask bitset mask = 0; while (*++masks) { int i = strchr(mask_names, *masks) - mask_names; if (i >= 0) { mask |= (1 << i); } } } // add watch wd = inotify_add_watch(pfd.fd, path, mask); if (wd < 0) { bb_perror_msg_and_die(&quot;add watch (%s) failed&quot;, path); } } static const char mask_names[] ALIGN1 = &quot;a&quot; // 0x00000001 File was accessed &quot;c&quot; // 0x00000002 File was modified &quot;e&quot; // 0x00000004 Metadata changed &quot;w&quot; // 0x00000008 Writtable file was closed &quot;0&quot; // 0x00000010 Unwrittable file closed &quot;r&quot; // 0x00000020 File was opened &quot;m&quot; // 0x00000040 File was moved from X &quot;y&quot; // 0x00000080 File was moved to Y &quot;n&quot; // 0x00000100 Subfile was created &quot;d&quot; // 0x00000200 Subfile was deleted &quot;D&quot; // 0x00000400 Self was deleted &quot;M&quot; // 0x00000800 Self was moved ; pfd.events = POLLIN; while (!signalled && poll(&pfd, 1, -1) > 0) { ssize_t len; void *buf; struct inotify_event *ie; // read out all pending events xioctl(pfd.fd, FIONREAD, &len); #define eventbuf bb_common_bufsiz1 ie = buf = (len <= sizeof(eventbuf)) ? eventbuf : xmalloc(len); len = full_read(pfd.fd, buf, len); // process events. N.B. events may vary in length while (len > 0) { int i; char events[12]; char *s = events; unsigned m = ie->mask; for (i = 0; i < 12; ++i, m >>= 1) { if (m & 1) { *s++ = mask_names[i]; } } *s = ''; args[1] = events; args[2] = watched[ie->wd]; args[3] = ie->len ? ie->name : NULL; xspawn((char **)args); // next event i = sizeof(struct inotify_event) + ie->len; len -= i; ie = (void*)((char*)ie + i); } if (eventbuf != buf) free(buf); } return EXIT_SUCCESS; }

14. IP Address Casting struct sockaddr { sa_family_t sa_family; char sa_data[14]; } struct sockaddr_in { sa_family_t sin_family; /* AF_INET */ uint16_t sin_port; /* port */ struct in_addr sin_addr; }; struct in_addr { uint32_t s_addr; }; struct sockaddr_in6 { uint16_t sin6_family; /* AF_INET6 */ uint16_t sin6_port; /* port */ uint32_t sin6_flowinfo; struct in6_addr sin6_addr; uint32_t sin6_scope_id; }; struct in6_addr { unsigned char s6_addr[16]; }; IPV4 IPV6

20. Socket States Stevens et al