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#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#define fail() exit(EXIT_FAILURE)
#define fail_clean() do { status = EXIT_FAILURE; goto finally; } while (0)
int main(int argc, char *argv[]) {
int status = EXIT_SUCCESS;
int fd, kq, n, i;
struct kevent event;
setbuf(stdout, NULL); // disable buffering even non-interactively
if (argc < 2) {
fprintf(stderr, "usage: %s file\n", argv[0]);
fail();
}
// 1. Open file
if ((fd = open(argv[1], O_RDONLY)) == -1) {
perror(argv[1]);
fail();
}
if (pledge("stdio", NULL) == -1) {
perror("pledge");
fail_clean();
}
if ((kq = kqueue()) == -1) {
perror("kqueue");
fail_clean();
}
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
};
// 2. Register event to watch for
if (kevent(kq, &change, 1, NULL, 0, NULL) == -1) {
perror("kevent");
fail_clean();
}
if (change.flags & EV_ERROR) {
fprintf(stderr, "Event error: %s", strerror(change.data));
fail_clean();
}
while (1) {
// 3. Wait for event
if ((n = kevent(kq, NULL, 0, &event, 1, NULL)) != 1) {
perror("kevent wait");
fail_clean();
} else 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_clean();
}
}
}
finally:
if (close(kq) == -1) {
perror("close");
fail();
}
if (close(fd) == -1) {
perror("close");
fail();
}
exit(status);
}
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