inotify_add_watch

       #include <sys/inotify.h>

       int inotify_add_watch(int fd, const char *pathname, uint32_t mask);

DESCRIPTION
       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 descrip-
       tor referring to the inotify instance whose watch list is to  be  modi-
       fied.   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  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 is returned.

       The  watch  descriptor  is  returned by later read(2)s from the inotify
       file descriptor.  These reads fetch inotify_event structures (see  ino-
       tify(7)) indicating filesystem events; the watch descriptor inside this
       structure identifies the object for which the event occurred.

RETURN VALUE
       On success, inotify_add_watch() returns a nonnegative watch descriptor.
       On error, -1 is returned and errno is set appropriately.

ERRORS
       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 descriptor.

       ENAMETOOLONG
              pathname is too long.

       ENOENT A  directory  component  in pathname does not exist or is a dan-
              gling 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.

VERSIONS
       Inotify was merged into the 2.6.13 Linux kernel.

Linux                             2014-07-08              INOTIFY_ADD_WATCH(2)
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