first stab at a simple file monitor using kqueue

.gitignore

@@ -0,0 +1 @@
+kqfm

Makefile

@@ -0,0 +1 @@
+kqfm: kqfm.c

kqfm.c

@@ -0,0 +1,132 @@
+#include <sys/types.h>
+#include <sys/event.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <getopt.h>
+#include <libgen.h>
+#include <fcntl.h>
+#include <err.h>
+#include <errno.h>
+
+const char* program_name;
+
+const struct option longopts[] = {
+    {"help", no_argument, NULL, 'h'},
+    {NULL,   0,           NULL, 0}
+};
+
+#define MIN_PATHS 1024
+char **paths;
+size_t paths_size = MIN_PATHS * sizeof(char *);
+
+void print_usage(FILE * stream)
+{
+    fprintf(stream, "%s: takes newline delimited filenames to watch on stdin "
+                    "and reports changes on stdout\n", program_name);
+    fprintf(stream, "usage: %s options \n", program_name);
+    fprintf(stream,
+           "  -h  --help             Display this usage information.\n");
+}
+
+void parse_options(int argc, char *argv[])
+{
+    int optchar;
+
+    while ((optchar = getopt_long(argc, argv, "h", longopts, NULL)) != -1) {
+        switch(optchar) {
+            case '?':
+            case 'h':
+                print_usage(stdout);
+                exit(0);
+            default:
+                break;
+        }
+    }
+}
+
+void register_path(int kq, char *path)
+{
+    struct kevent k_fchange;
+    int fd = open("/private/tmp/test", O_EVTONLY);
+
+    if (fd == -1) {
+        err(errno, "couldn't open %s", path);
+    }
+
+    EV_SET(&k_fchange, fd, EVFILT_VNODE, EV_ADD | EV_CLEAR, 
+        NOTE_DELETE | NOTE_WRITE, 0, path);
+
+    if (kevent(kq, &k_fchange, 1, NULL, 0, NULL) == -1) {
+        err(1, "couldn't monitor %s", path);
+    }
+}
+
+void register_paths(int kq, FILE * in)
+{
+    char **write_ptr = NULL;
+    size_t write_space = 0;
+
+    if (write_ptr == NULL) {
+        write_ptr = (char**)&paths;
+    }
+
+    while(getline(write_ptr, &write_space, in) > 0) {
+        register_path(kq, *write_ptr);
+
+        if ((uintptr_t)++write_ptr > ((uintptr_t)&paths + paths_size - 1)) {
+            paths = realloc(paths, paths_size + MIN_PATHS * sizeof(char *));
+            if (paths == NULL) {
+                err(errno, "couldn't reallocate memory for paths");
+            }
+
+            write_ptr = (char **)((uintptr_t)&paths + paths_size);
+            paths_size = paths_size + paths_size;
+        }
+    }
+}
+
+void handle_event(struct kevent event)
+{
+
+}
+
+void watcher_loop(FILE * in, FILE * out)
+{
+    struct kevent k_input;
+    struct kevent k_event;
+    int kq;
+    int in_fno = fileno(in);
+
+    kq = kqueue();
+    if (kq == -1) { err(1, "couldn't get kqueue"); }
+
+    EV_SET(&k_input, in_fno, EVFILT_READ, EV_ADD | EV_CLEAR, 0, 0, NULL);
+    if (kevent(kq, &k_input, 1, NULL, 0, NULL) == -1) {
+        err(1, "couldn't set input event");
+    }
+
+    while (1) {
+        if (kevent(kq, NULL, 0, &k_event, 1, NULL) == -1) {
+            err(1, "error checking kqueue");
+        }
+        if (k_event.ident == in_fno && k_event.filter == EVFILT_READ) {
+            register_paths(kq, in);
+        } else {
+            handle_event(k_event);
+        }
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    program_name = basename(argv[0]);
+    parse_options(argc, argv);
+
+    paths = malloc(paths_size);
+    if (paths == NULL) {
+        err(errno, "couldn't allocate memory for paths");
+    }
+
+    watcher_loop(stdin, stdout);
+}