//! Monitoring API for filesystem events.
//!
//! Inotify is a Linux-only API to monitor filesystems events.
//!
//! For more documentation, please read [inotify(7)](https://man7.org/linux/man-pages/man7/inotify.7.html).
//!
//! # Examples
//!
//! Monitor all events happening in directory "test":
//! ```no_run
//! # use nix::sys::inotify::{AddWatchFlags,InitFlags,Inotify};
//! #
//! // We create a new inotify instance.
//! let instance = Inotify::init(InitFlags::empty()).unwrap();
//!
//! // We add a new watch on directory "test" for all events.
//! let wd = instance.add_watch("test", AddWatchFlags::IN_ALL_EVENTS).unwrap();
//!
//! loop {
//! // We read from our inotify instance for events.
//! let events = instance.read_events().unwrap();
//! println!("Events: {:?}", events);
//! }
//! ```
use crate::errno::Errno;
use crate::unistd::read;
use crate::NixPath;
use crate::Result;
use cfg_if::cfg_if;
use libc::{c_char, c_int};
use std::ffi::{CStr, OsStr, OsString};
use std::mem::{size_of, MaybeUninit};
use std::os::unix::ffi::OsStrExt;
use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
use std::ptr;
libc_bitflags! {
/// Configuration options for [`inotify_add_watch`](fn.inotify_add_watch.html).
pub struct AddWatchFlags: u32 {
/// File was accessed.
IN_ACCESS;
/// File was modified.
IN_MODIFY;
/// Metadata changed.
IN_ATTRIB;
/// Writable file was closed.
IN_CLOSE_WRITE;
/// Nonwritable file was closed.
IN_CLOSE_NOWRITE;
/// File was opened.
IN_OPEN;
/// File was moved from X.
IN_MOVED_FROM;
/// File was moved to Y.
IN_MOVED_TO;
/// Subfile was created.
IN_CREATE;
/// Subfile was deleted.
IN_DELETE;
/// Self was deleted.
IN_DELETE_SELF;
/// Self was moved.
IN_MOVE_SELF;
/// Backing filesystem was unmounted.
IN_UNMOUNT;
/// Event queue overflowed.
IN_Q_OVERFLOW;
/// File was ignored.
IN_IGNORED;
/// Combination of `IN_CLOSE_WRITE` and `IN_CLOSE_NOWRITE`.
IN_CLOSE;
/// Combination of `IN_MOVED_FROM` and `IN_MOVED_TO`.
IN_MOVE;
/// Only watch the path if it is a directory.
IN_ONLYDIR;
/// Don't follow symlinks.
IN_DONT_FOLLOW;
/// Event occurred against directory.
IN_ISDIR;
/// Only send event once.
IN_ONESHOT;
/// All of the events.
IN_ALL_EVENTS;
}
}
libc_bitflags! {
/// Configuration options for [`inotify_init1`](fn.inotify_init1.html).
pub struct InitFlags: c_int {
/// Set the `FD_CLOEXEC` flag on the file descriptor.
IN_CLOEXEC;
/// Set the `O_NONBLOCK` flag on the open file description referred to by the new file descriptor.
IN_NONBLOCK;
}
}
/// An inotify instance. This is also a file descriptor, you can feed it to
/// other interfaces consuming file descriptors, epoll for example.
#[derive(Debug, Clone, Copy)]
pub struct Inotify {
fd: RawFd,
}
/// This object is returned when you create a new watch on an inotify instance.
/// It is then returned as part of an event once triggered. It allows you to
/// know which watch triggered which event.
#[derive(Debug, Clone, Copy, Hash, Eq, PartialEq, Ord, PartialOrd)]
pub struct WatchDescriptor {
wd: i32,
}
/// A single inotify event.
///
/// For more documentation see, [inotify(7)](https://man7.org/linux/man-pages/man7/inotify.7.html).
#[derive(Debug)]
pub struct InotifyEvent {
/// Watch descriptor. This field corresponds to the watch descriptor you
/// were issued when calling add_watch. It allows you to know which watch
/// this event comes from.
pub wd: WatchDescriptor,
/// Event mask. This field is a bitfield describing the exact event that
/// occured.
pub mask: AddWatchFlags,
/// This cookie is a number that allows you to connect related events. For
/// now only IN_MOVED_FROM and IN_MOVED_TO can be connected.
pub cookie: u32,
/// Filename. This field exists only if the event was triggered for a file
/// inside the watched directory.
pub name: Option<OsString>,
}
impl Inotify {
/// Initialize a new inotify instance.
///
/// Returns a Result containing an inotify instance.
///
/// For more information see, [inotify_init(2)](https://man7.org/linux/man-pages/man2/inotify_init.2.html).
pub fn init(flags: InitFlags) -> Result<Inotify> {
let res = Errno::result(unsafe { libc::inotify_init1(flags.bits()) });
res.map(|fd| Inotify { fd })
}
/// Adds a new watch on the target file or directory.
///
/// Returns a watch descriptor. This is not a File Descriptor!
///
/// For more information see, [inotify_add_watch(2)](https://man7.org/linux/man-pages/man2/inotify_add_watch.2.html).
pub fn add_watch<P: ?Sized + NixPath>(
self,
path: &P,
mask: AddWatchFlags,
) -> Result<WatchDescriptor> {
let res = path.with_nix_path(|cstr| unsafe {
libc::inotify_add_watch(self.fd, cstr.as_ptr(), mask.bits())
})?;
Errno::result(res).map(|wd| WatchDescriptor { wd })
}
/// Removes an existing watch using the watch descriptor returned by
/// inotify_add_watch.
///
/// Returns an EINVAL error if the watch descriptor is invalid.
///
/// For more information see, [inotify_rm_watch(2)](https://man7.org/linux/man-pages/man2/inotify_rm_watch.2.html).
pub fn rm_watch(self, wd: WatchDescriptor) -> Result<()> {
cfg_if! {
if #[cfg(target_os = "linux")] {
let arg = wd.wd;
} else if #[cfg(target_os = "android")] {
let arg = wd.wd as u32;
}
}
let res = unsafe { libc::inotify_rm_watch(self.fd, arg) };
Errno::result(res).map(drop)
}
/// Reads a collection of events from the inotify file descriptor. This call
/// can either be blocking or non blocking depending on whether IN_NONBLOCK
/// was set at initialization.
///
/// Returns as many events as available. If the call was non blocking and no
/// events could be read then the EAGAIN error is returned.
pub fn read_events(self) -> Result<Vec<InotifyEvent>> {
let header_size = size_of::<libc::inotify_event>();
const BUFSIZ: usize = 4096;
let mut buffer = [0u8; BUFSIZ];
let mut events = Vec::new();
let mut offset = 0;
let nread = read(self.fd, &mut buffer)?;
while (nread - offset) >= header_size {
let event = unsafe {
let mut event = MaybeUninit::<libc::inotify_event>::uninit();
ptr::copy_nonoverlapping(
buffer.as_ptr().add(offset),
event.as_mut_ptr() as *mut u8,
(BUFSIZ - offset).min(header_size),
);
event.assume_init()
};
let name = match event.len {
0 => None,
_ => {
let ptr = unsafe {
buffer.as_ptr().add(offset + header_size)
as *const c_char
};
let cstr = unsafe { CStr::from_ptr(ptr) };
Some(OsStr::from_bytes(cstr.to_bytes()).to_owned())
}
};
events.push(InotifyEvent {
wd: WatchDescriptor { wd: event.wd },
mask: AddWatchFlags::from_bits_truncate(event.mask),
cookie: event.cookie,
name,
});
offset += header_size + event.len as usize;
}
Ok(events)
}
}
impl AsRawFd for Inotify {
fn as_raw_fd(&self) -> RawFd {
self.fd
}
}
impl FromRawFd for Inotify {
unsafe fn from_raw_fd(fd: RawFd) -> Self {
Inotify { fd }
}
}