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       inotify_add_watch - add a watch to an initialized inotify instance


       #include <sys/inotify.h>

       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  the unique watch
       descriptor associated with pathname  for  this  inotify  instance.   If
       pathname  was  not  previously  being watched by this inotify instance,
       then the watch descriptor is newly allocated.  If pathname was  already
       being  watched, 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
       inotify(7)) indicating file system 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.


       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

       EINVAL The  given  event mask contains no valid events; or fd is not an
              inotify file descriptor.

       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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