inotify_add_watch(2) - phpMan
INOTIFY_ADD_WATCH(2) Linux Programmer's Manual INOTIFY_ADD_WATCH(2)
inotify_add_watch - add a watch to an initialized inotify instance
int inotify_add_watch(int fd, const char *pathname, uint32_t mask);
inotify_add_watch() 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 ino‐
tify instance, for the filesystem object that corresponds to pathname. If the filesystem
object was not previously being watched by this inotify instance, then the watch descrip‐
tor 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 is
The watch descriptor is returned by later read(2)s from the inotify file descriptor.
These reads fetch inotify_event structures (see inotify(7)) indicating filesystem events;
the watch descriptor inside this structure identifies the object for which the event
On success, inotify_add_watch() returns a nonnegative watch descriptor. On error, -1 is
returned and errno is set appropriately.
EACCES Read access to the given file is not permitted.
EBADF The given file descriptor is not valid.
EFAULT pathname points outside of the process's accessible address space.
EINVAL The given event mask contains no valid events; or fd is not an inotify file
pathname is too long.
ENOENT A directory component in pathname does not exist or is a dangling symbolic link.
ENOMEM Insufficient kernel memory was available.
ENOSPC 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.
inotify_init(2), inotify_rm_watch(2), inotify(7)
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Linux 2014-07-08 INOTIFY_ADD_WATCH(2)