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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |EXAMPLES |NOTES |HISTORY |SEE ALSO |COLOPHON | |
SD_EVENT_ADD_INOTIFY(3) sd_event_add_inotifySD_EVENT_ADD_INOTIFY(3)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
#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_tmask,sd_event_inotify_handler_thandler,void *userdata);int sd_event_add_inotify_fd(sd_event *event,sd_event_source **source, intfd,uint32_tmask,sd_event_inotify_handler_thandler,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);
sd_event_add_inotify()adds a newinotify(7) file system inode event source to an event loop. The event loop object is specified in theevent parameter, the event source object is returned in thesource parameter. Thepath parameter specifies the path of the file system inode to watch. Themask parameter specifies which types of inode events to watch specifically. It must contain an OR-ed combination ofIN_ACCESS,IN_ATTRIB,IN_CLOSE_WRITE, ... flags. Seeinotify(7) for further information. Thehandler must reference a function to call when the inode changes orNULL. The handler function will be passed theuserdata 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. Ifhandler isNULL, a default handler that callssd_event_exit(3) will be used.sd_event_add_inotify_fd()is identical tosd_event_add_inotify(), except that it takes a file descriptor to an inode (possibly anO_PATHone, 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 ofIN_MASK_ADD. The handler is enabled continuously (SD_EVENT_ON), but this may be changed withsd_event_source_set_enabled(3). Alternatively, theIN_ONESHOTmask flag may be used to requestSD_EVENT_ONESHOTmode. If the handler function returns a negative error code, it will be disabled after the invocation, even if theSD_EVENT_ONmode was requested before. As a special limitation the priority of inotify event sources may only be altered (seesd_event_source_set_priority(3)) in the time between creation of the event source object withsd_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 usesd_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 withsd_event_source_set_enabled(3). If the second parameter ofsd_event_add_inotify()is passed asNULLno 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 thehandler parameter tosd_event_add_inotify()isNULL, and the event source fires, this will be considered a request to exit the event loop. In this case, theuserdata parameter, cast to an integer, is passed as the exit code parameter tosd_event_exit(3).sd_event_source_get_inotify_mask()retrieves the configured inotify watch mask of an event source created previously withsd_event_add_inotify(). It takes the event source object as thesource parameter and a pointer to auint32_tvariable 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 withsd_event_add_inotify(). It takes the event source object as thesource parameter and a pointer to aconst char **variable to return the path in. The caller must not free the returned path.
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 withIN_MASK_ADDset.-ESTALE Returned bysd_event_source_add_inotify()orsd_event_source_add_inotify_fd()when the event loop is already terminated. Returned bysd_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.-ENOSYSsd_event_add_inotify_fd()orsd_event_source_get_inotify_path()was called without /proc/ mounted.
Example 1. A simple program that uses inotify to monitor one ortwo 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; }Functions described here are available as a shared library, which can be compiled against and linked to with thelibsystemd pkg-config(1) file. The code described here usesgetenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not callsetenv(3) from a parallel thread. It is recommended to only do calls tosetenv()from an early phase of the program when no other threads have been started.
sd_event_inotify_handler_t(),sd_event_add_inotify(), andsd_event_source_get_inotify_mask()were added in version 239.sd_event_add_inotify_fd()was added in version 250.sd_event_source_get_inotify_path()was added in version 256.
systemd(1),sd-event(3),sd_event_new(3),sd_event_now(3),sd_event_add_io(3),sd_event_add_time(3),sd_event_add_signal(3),sd_event_add_defer(3),sd_event_add_child(3),sd_event_source_set_enabled(3),sd_event_source_set_priority(3),sd_event_source_set_userdata(3),sd_event_source_set_description(3),sd_event_source_set_floating(3),waitid(2)
This page is part of thesystemd (systemd system and service manager) project. Information about the project can be found at ⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug report for this manual page, see ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This page was obtained from the project's upstream Git repository ⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-08-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgsystemd 258~rc2SD_EVENT_ADD_INOTIFY(3)Pages that refer to this page:sd-event(3), sd_event_add_child(3), sd_event_add_defer(3), sd_event_add_io(3), sd_event_add_memory_pressure(3), sd_event_add_signal(3), sd_event_add_time(3), sd_event_exit(3), sd_event_new(3), sd_event_run(3), sd_event_set_watchdog(3), sd_event_source_get_event(3), sd_event_source_get_pending(3), sd_event_source_set_description(3), sd_event_source_set_destroy_callback(3), sd_event_source_set_enabled(3), sd_event_source_set_exit_on_failure(3), sd_event_source_set_floating(3), sd_event_source_set_prepare(3), sd_event_source_set_priority(3), sd_event_source_set_ratelimit(3), sd_event_source_set_userdata(3), sd_event_source_unref(3), sd_event_wait(3), systemd.directives(7), systemd.index(7)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |