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INOTIFY_ADD_WATCH(2) Linux Programmer's Manual INOTIFY_ADD_WATCH(2)
NAME
inotify_add_watch - add a watch to an initialized inotify instance
SYNOPSIS
#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 descriptor referring to the inotify instance whose watch list is to be modified. The events to be monitored for path‐
name 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 path‐
name. If the filesystem object was not previously being watched by this inotify instance, then the watch descriptor is newly allocated. If the filesystem ob‐
ject 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.
RETURN VALUE
On success, inotify_add_watch() returns a watch descriptor (a nonnegative integer). On error, -1 is returned and errno is set to indicate the error.
ERRORS
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 space.
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.
ENAMETOOLONG
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.
ENOTDIR
mask contains IN_ONLYDIR and pathname is not a directory.
VERSIONS
Inotify was merged into the 2.6.13 Linux kernel.
CONFORMING TO
This system call is Linux-specific.
EXAMPLES
See inotify(7).
SEE ALSO
inotify_init(2), inotify_rm_watch(2), inotify(7)
Linux 2021-03-22 INOTIFY_ADD_WATCH(2)