sd_event_add_inotify(3)

1SD_EVENT_ADD_INOTIFY(3)      sd_event_add_inotify      SD_EVENT_ADD_INOTIFY(3)
2
3
4

NAME

6       sd_event_add_inotify, sd_event_source_get_inotify_mask,
7       sd_event_inotify_handler_t - Add an "inotify" file system inode event
8       source to an event loop
9

SYNOPSIS

11       #include <systemd/sd-event.h>
12
13       typedef struct sd_event_source sd_event_source;
14
15       typedef int (*sd_event_inotify_handler_t)(sd_event_source *s,
16                                                 const struct inotify_event *event,
17                                                 void *userdata);
18
19       int sd_event_add_inotify(sd_event *event, sd_event_source **source,
20                                const char *path, uint32_t mask,
21                                sd_event_inotify_handler_t handler,
22                                void *userdata);
23
24       int sd_event_source_get_inotify_mask(sd_event_source *source,
25                                            uint32_t *mask);
26

DESCRIPTION

28       sd_event_add_inotify() adds a new inotify(7) file system inode event
29       source to an event loop. The event loop object is specified in the
30       event parameter, the event source object is returned in the source
31       parameter. The path parameter specifies the path of the file system
32       inode to watch. The handler must reference a function to call when the
33       inode changes. The handler function will be passed the userdata
34       pointer, which may be chosen freely by the caller. The handler also
35       receives a pointer to a struct inotify_event structure containing
36       information about the inode event. The mask parameter specifies which
37       types of inode events to watch specifically. It must contain an OR-ed
38       combination of IN_ACCESS, IN_ATTRIB, IN_CLOSE_WRITE, ... flags. See
39       inotify(7) for further information.
40
41       If multiple event sources are installed for the same inode the backing
42       inotify watch descriptor is automatically shared. The mask parameter
43       may contain any flag defined by the inotify API, with the exception of
44       IN_MASK_ADD.
45
46       The handler is enabled continuously (SD_EVENT_ON), but this may be
47       changed with sd_event_source_set_enabled(3). Alternatively, the
48       IN_ONESHOT mask flag may be used to request SD_EVENT_ONESHOT mode. If
49       the handler function returns a negative error code, it will be disabled
50       after the invocation, even if the SD_EVENT_ON mode was requested
51       before.
52
53       As a special limitation the priority of inotify event sources may only
54       be altered (see sd_event_source_set_priority(3)) in the time between
55       creation of the event source object with sd_event_add_inotify() and the
56       beginning of the next event loop iteration. Attempts of changing the
57       priority any later will be refused. Consider freeing and allocating a
58       new inotify event source to change the priority at that point.
59
60       To destroy an event source object use sd_event_source_unref(3), but
61       note that the event source is only removed from the event loop when all
62       references to the event source are dropped. To make sure an event
63       source does not fire anymore, even when there's still a reference to it
64       kept, consider disabling it with sd_event_source_set_enabled(3).
65
66       If the second parameter of sd_event_add_inotify() is passed as NULL no
67       reference to the event source object is returned. In this case the
68       event source is considered "floating", and will be destroyed implicitly
69       when the event loop itself is destroyed.
70
71       If the handler parameter to sd_event_add_inotify() is NULL, and the
72       event source fires, this will be considered a request to exit the event
73       loop. In this case, the userdata parameter, cast to an integer, is
74       passed as the exit code parameter to sd_event_exit(3).
75
76       sd_event_source_get_inotify_mask() retrieves the configured inotify
77       watch mask of an event source created previously with
78       sd_event_add_inotify(). It takes the event source object as the source
79       parameter and a pointer to a uint32_t variable to return the mask in.
80

RETURN VALUE

82       On success, these functions return 0 or a positive integer. On failure,
83       they return a negative errno-style error code.
84
85   Errors
86       Returned errors may indicate the following problems:
87
88       -ENOMEM
89           Not enough memory to allocate an object.
90
91       -EINVAL
92           An invalid argument has been passed. This includes specifying a
93           mask with IN_MASK_ADD set.
94
95       -ESTALE
96           The event loop is already terminated.
97
98       -ECHILD
99           The event loop has been created in a different process.
100
101       -EDOM
102           The passed event source is not an inotify process event source.
103

EXAMPLES

105       Example 1. A simple program that uses inotify to monitor one or two
106       directories
107
108           #include <stdio.h>
109           #include <string.h>
110           #include <sys/inotify.h>
111
112           #include <systemd/sd-event.h>
113
114           #define _cleanup_(f) __attribute__((cleanup(f)))
115
116           static int inotify_handler(sd_event_source *source,
117                                      const struct inotify_event *event,
118                                      void *userdata) {
119
120             const char *desc = NULL;
121
122             sd_event_source_get_description(source, &desc);
123
124             if (event->mask & IN_Q_OVERFLOW)
125               printf("inotify-handler <%s>: overflow\n", desc);
126             else if (event->mask & IN_CREATE)
127               printf("inotify-handler <%s>: create on %s\n", desc, event->name);
128             else if (event->mask & IN_DELETE)
129               printf("inotify-handler <%s>: delete on %s\n", desc, event->name);
130             else if (event->mask & IN_MOVED_TO)
131               printf("inotify-handler <%s>: moved-to on %s\n", desc, event->name);
132
133             /* Terminate the program if an "exit" file appears */
134             if ((event->mask & (IN_CREATE|IN_MOVED_TO)) &&
135                 strcmp(event->name, "exit") == 0)
136               sd_event_exit(sd_event_source_get_event(source), 0);
137
138             return 1;
139           }
140
141           int main(int argc, char **argv) {
142             _cleanup_(sd_event_unrefp) sd_event *event = NULL;
143             _cleanup_(sd_event_source_unrefp) sd_event_source *source1 = NULL, *source2 = NULL;
144
145             const char *path1 = argc > 1 ? argv[1] : "/tmp";
146             const char *path2 = argc > 2 ? argv[2] : NULL;
147
148             /* Note: failure handling is omitted for brevity */
149
150             sd_event_default(&event);
151
152             sd_event_add_inotify(event, &source1, path1,
153                                  IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_TO,
154                                  inotify_handler, NULL);
155             if (path2)
156               sd_event_add_inotify(event, &source2, path2,
157                                    IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_TO,
158                                    inotify_handler, NULL);
159
160             sd_event_loop(event);
161
162             return 0;
163           }
164

NOTES

166       These APIs are implemented as a shared library, which can be compiled
167       and linked to with the libsystemd pkg-config(1) file.
168

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

EXAMPLES

NOTES

SEE ALSO