INOTIFY_ADD_WATCH(2)       Linux Programmer's Manual      INOTIFY_ADD_WATCH(2)

       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 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 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 filesystem events; the watch descriptor inside
       this structure identifies the object for which the event occurred.

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

       EACCES Read access to the given file is not permitted.

       EBADF  The given file descriptor is not valid.

       EEXIST mask contains IN_MASK_CREATE and pathname refers to a file
              already being watched by the same fd.

       EFAULT pathname points outside of the process's accessible address

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

              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.

              mask contains IN_ONLYDIR and pathname is not a directory.

       Inotify was merged into the 2.6.13 Linux kernel.

       This system call is Linux-specific.

       See inotify(7).

       inotify_init(2), inotify_rm_watch(2), inotify(7)

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                             2020-04-11              INOTIFY_ADD_WATCH(2)