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
the caller must have read permission for this file.
argument is a file descriptor referring to the
inotify instance whose watch list is to be modified.
The events to be monitored for
are specified in the
for a description of the bits that can be set in
A successful call to
returns the unique watch descriptor associated with
for this inotify instance.
was not previously being watched by this inotify instance,
then the watch descriptor is newly allocated.
was already being watched, then the descriptor
for the existing watch is returned.
The watch descriptor is returned by later
from the inotify file descriptor.
These reads fetch
indicating file system events;
the watch descriptor inside this structure identifies
the object for which the event occurred.
returns a nonnegative watch descriptor.
On error -1 is returned and
is set appropriately.
Read access to the given file is not permitted.
The given file descriptor is not valid.
points outside of the process's accessible address space.
The given event mask contains no valid events; or
is not an inotify file descriptor.
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.