inotify_add_watch - add a watch to an initialized inotify instance
int inotify_add_watch(int fd, const char
*pathname, uint32_t mask);
() adds a new watch, or modifies an existing watch, for
the file whose location is specified in pathname
; the caller must have
read permission for this file. The fd
argument is a file descriptor
referring to the inotify instance whose watch list is to be modified. The
events to be monitored for pathname
are specified in the mask
bit-mask argument. See inotify
(7) for a description of the bits that
can be set in mask
A successful call to inotify_add_watch
() returns a unique watch
descriptor for this inotify instance, for the filesystem object (inode) that
corresponds to pathname
. If the filesystem object was not previously
being watched by this inotify instance, then the watch descriptor is newly
allocated. If the filesystem object was already being watched (perhaps via a
different link to the same object), then the descriptor for the existing watch
The watch descriptor is returned by later read
(2)s from the inotify file
descriptor. These reads fetch inotify_event
(7)) indicating filesystem events; the watch descriptor inside
this structure identifies the object for which the event occurred.
On success, inotify_add_watch
() returns a nonnegative watch descriptor.
On error, -1 is returned and errno
is set appropriately.
- Read access to the given file is not permitted.
- The given file descriptor is not valid.
- pathname points outside of the process's accessible
- The given event mask contains no valid events; or fd
is not an inotify file descriptor.
- pathname is too long.
- A directory component in pathname does not exist or
is a dangling symbolic link.
- Insufficient kernel memory was available.
- The user limit on the total number of inotify watches was
reached or the kernel failed to allocate a needed resource.
Inotify was merged into the 2.6.13 Linux kernel.
This system call is Linux-specific.
This page is part of release 4.13 of the Linux man-pages
description of the project, information about reporting bugs, and the latest
version of this page, can be found at