# sd_event_add_inotify

## NAME



           sd_event_add_inotify, sd_event_add_inotify_fd,
           sd_event_source_get_inotify_mask,
           sd_event_source_get_inotify_path, sd_event_inotify_handler_t - Add
           an "inotify" file system inode event source to an event loop
    


## SYNOPSIS



           **#include <systemd/sd-event.h>**
    
           **typedef struct sd_event_source sd_event_source;**
    
           **typedef int (*sd_event_inotify_handler_t)(sd_event_source ***_s_**,**
                                                     **const struct inotify_event ***_event_**,**
                                                     **void ***_userdata_**);**
    
           **int sd_event_add_inotify(sd_event ***_event_**,**
                                    **sd_event_source ****_source_**,**
                                    **const char ***_path_**, uint32_t** _mask_**,**
                                    **sd_event_inotify_handler_t** _handler_**,**
                                    **void ***_userdata_**);**
    
           **int sd_event_add_inotify_fd(sd_event ***_event_**,**
                                       **sd_event_source ****_source_**, int** _fd_**,**
                                       **uint32_t** _mask_**,**
                                       **sd_event_inotify_handler_t** _handler_**,**
                                       **void ***_userdata_**);**
    
           **int sd_event_source_get_inotify_mask(sd_event_source ***_source_**,**
                                                **uint32_t ***_ret_**);**
    
           **int sd_event_source_get_inotify_path(sd_event_source ***_source_**,**
                                                **const char ****_ret_**);**
    


## DESCRIPTION



           **sd_event_add_inotify()** adds a new inotify(7) file system inode
           event source to an event loop. The event loop object is specified
           in the _event_ parameter, the event source object is returned in the
           _source_ parameter. The _path_ parameter specifies the path of the
           file system inode to watch. The _mask_ parameter specifies which
           types of inode events to watch specifically. It must contain an
           OR-ed combination of **IN_ACCESS** , **IN_ATTRIB** , **IN_CLOSE_WRITE** , ...
           flags. See inotify(7) for further information.
    
           The _handler_ must reference a function to call when the inode
           changes or **NULL**. The handler function will be passed the _userdata_
           pointer, which may be chosen freely by the caller. The handler
           also receives a pointer to a struct inotify_event structure
           containing information about the inode event. The handler may
           return negative to signal an error (see below), other return
           values are ignored. If _handler_ is **NULL** , a default handler that
           calls sd_event_exit(3) will be used.
    
           **sd_event_add_inotify_fd()** is identical to **sd_event_add_inotify()** ,
           except that it takes a file descriptor to an inode (possibly an
           **O_PATH** one, but any other will do too) instead of a path in the
           file system.
    
           If multiple event sources are installed for the same inode the
           backing inotify watch descriptor is automatically shared. The mask
           parameter may contain any flag defined by the inotify API, with
           the exception of **IN_MASK_ADD**.
    
           The handler is enabled continuously (**SD_EVENT_ON**), but this may be
           changed with sd_event_source_set_enabled(3). Alternatively, the
           **IN_ONESHOT** mask flag may be used to request **SD_EVENT_ONESHOT** mode.
           If the handler function returns a negative error code, it will be
           disabled after the invocation, even if the **SD_EVENT_ON** mode was
           requested before.
    
           As a special limitation the priority of inotify event sources may
           only be altered (see sd_event_source_set_priority(3)) in the time
           between creation of the event source object with
           **sd_event_add_inotify()** and the beginning of the next event loop
           iteration. Attempts of changing the priority any later will be
           refused. Consider freeing and allocating a new inotify event
           source to change the priority at that point.
    
           To destroy an event source object use sd_event_source_unref(3),
           but note that the event source is only removed from the event loop
           when all references to the event source are dropped. To make sure
           an event source does not fire anymore, even when there's still a
           reference to it kept, consider disabling it with
           sd_event_source_set_enabled(3).
    
           If the second parameter of **sd_event_add_inotify()** is passed as
           **NULL** no reference to the event source object is returned. In this
           case, the event source is considered "floating", and will be
           destroyed implicitly when the event loop itself is destroyed.
    
           If the _handler_ parameter to **sd_event_add_inotify()** is **NULL** , and
           the event source fires, this will be considered a request to exit
           the event loop. In this case, the _userdata_ parameter, cast to an
           integer, is passed as the exit code parameter to sd_event_exit(3).
    
           **sd_event_source_get_inotify_mask()** retrieves the configured
           inotify watch mask of an event source created previously with
           **sd_event_add_inotify()**. It takes the event source object as the
           _source_ parameter and a pointer to a **uint32_t** variable to return
           the mask in.
    
           **sd_event_source_get_inotify_path()** retrieves the target path of
           the configured inotify watch of an event source created previously
           with **sd_event_add_inotify()**. It takes the event source object as
           the _source_ parameter and a pointer to a **const char **** variable to
           return the path in. The caller must not free the returned path.
    


## RETURN VALUE



           On success, these functions return 0 or a positive integer. On
           failure, they return a negative errno-style error code.
    
       **Errors**
           Returned errors may indicate the following problems:
    
           **-ENOMEM**
               Not enough memory to allocate an object.
    
           **-EINVAL**
               An invalid argument has been passed. This includes specifying
               a mask with **IN_MASK_ADD** set.
    
           **-ESTALE**
               Returned by **sd_event_source_add_inotify()** or
               **sd_event_source_add_inotify_fd()** when the event loop is
               already terminated. Returned by
               **sd_event_source_get_inotify_path()** when no active inode data
               is assigned to the event source, e.g. when the event source is
               disabled.
    
           **-ECHILD**
               The event loop has been created in a different process,
               library or module instance.
    
           **-EDOM**
               The passed event source is not an inotify process event
               source.
    
           **-EBADF**
               The passed file descriptor is not valid.
    
           **-ENOSYS**
               **sd_event_add_inotify_fd()** or
               **sd_event_source_get_inotify_path()** was called without /proc/
               mounted.
    


## EXAMPLES



           **Example 1. A simple program that uses inotify to monitor one or**
           **two directories**
    
               /* SPDX-License-Identifier: MIT-0 */
    
               #include <stdio.h>
               #include <string.h>
               #include <sys/inotify.h>
    
               #include <systemd/sd-event.h>
    
               #define _cleanup_(f) __attribute__((cleanup(f)))
    
               static int inotify_handler(sd_event_source *source,
                                          const struct inotify_event *event,
                                          void *userdata) {
    
                 const char *desc = NULL;
    
                 sd_event_source_get_description(source, &desc);
    
                 if (event->mask & IN_Q_OVERFLOW)
                   printf("inotify-handler <%s>: overflow\n", desc);
                 else if (event->mask & IN_CREATE)
                   printf("inotify-handler <%s>: create on %s\n", desc, event->name);
                 else if (event->mask & IN_DELETE)
                   printf("inotify-handler <%s>: delete on %s\n", desc, event->name);
                 else if (event->mask & IN_MOVED_TO)
                   printf("inotify-handler <%s>: moved-to on %s\n", desc, event->name);
    
                 /* Terminate the program if an "exit" file appears */
                 if ((event->mask & (IN_CREATE|IN_MOVED_TO)) &&
                     strcmp(event->name, "exit") == 0)
                   sd_event_exit(sd_event_source_get_event(source), 0);
    
                 return 1;
               }
    
               int main(int argc, char **argv) {
                 _cleanup_(sd_event_unrefp) sd_event *event = NULL;
                 _cleanup_(sd_event_source_unrefp) sd_event_source *source1 = NULL, *source2 = NULL;
    
                 const char *path1 = argc > 1 ? argv[1] : "/tmp";
                 const char *path2 = argc > 2 ? argv[2] : NULL;
    
                 /* Note: failure handling is omitted for brevity */
    
                 sd_event_default(&event);
    
                 sd_event_add_inotify(event, &source1, path1,
                                      IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_TO,
                                      inotify_handler, NULL);
                 if (path2)
                   sd_event_add_inotify(event, &source2, path2,
                                        IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_TO,
                                        inotify_handler, NULL);
    
                 sd_event_loop(event);
    
                 return 0;
               }
    


## NOTES



           Functions described here are available as a shared library, which
           can be compiled against and linked to with the
           **libsystemd pkg-config**(1) file.
    
           The code described here uses getenv(3), which is declared to be
           not multi-thread-safe. This means that the code calling the
           functions described here must not call setenv(3) from a parallel
           thread. It is recommended to only do calls to **setenv()** from an
           early phase of the program when no other threads have been
           started.
    


* * *