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#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#define try(x) if ((x) != -1) {}
void fail() {
exit(EXIT_FAILURE);
}
void fail_with_error(char *s) {
perror(s);
exit(EXIT_FAILURE);
}
int main(int argc, char *argv[]) {
setbuf(stdout, NULL); // disable buffering even non-interactively
if (argc < 2) {
fprintf(stderr, "usage: %s file\n", argv[0]);
fail();
}
int fd;
try (fd = open(argv[1], O_RDONLY)) else fail_with_error(argv[1]);
try (pledge("stdio", NULL)) else fail_with_error("pledge");
int kq;
try (kq = kqueue()) else fail_with_error("kqueue");
struct kevent change = { // event to watch for
.ident = fd,
.filter = EVFILT_VNODE,
.flags = EV_ADD | EV_CLEAR,
.fflags = NOTE_WRITE | NOTE_RENAME | NOTE_DELETE,
.data = 0,
.udata = NULL
};
// Register event to watch for
try (kevent(kq, &change, 1, NULL, 0, NULL)) else fail_with_error("kevent");
if (change.flags & EV_ERROR) {
fprintf(stderr, "event error: %s", strerror(change.data));
fail();
}
int n;
struct kevent event;
while (1) {
// Wait for event
try (n = kevent(kq, NULL, 0, &event, 1, NULL)) else fail_with_error("kevent wait");
if (n > 0) {
if (event.fflags & NOTE_WRITE)
printf("%s\n", argv[1]);
if (event.fflags & NOTE_RENAME)
fprintf(stderr, "note: file was renamed\n");
if (event.fflags & NOTE_DELETE) {
fprintf(stderr, "error: file was deleted\n");
fail();
}
}
}
exit(EXIT_SUCCESS);
// assume that the kernel closes the file descriptors
}