sd_event_source_get_inotify_mask(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 specifie 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       sd_event_source_get_inotify_mask() retrieves the configured inotify
72       watch mask of an event source created previously with
73       sd_event_add_inotify(). It takes the event source object as the source
74       parameter and a pointer to a uint32_t variable to return the mask in.
75

RETURN VALUE

77       On success, these functions return 0 or a positive integer. On failure,
78       they return a negative errno-style error code.
79

ERRORS

81       Returned errors may indicate the following problems:
82
83       -ENOMEM
84           Not enough memory to allocate an object.
85
86       -EINVAL
87           An invalid argument has been passed. This includes specifying a
88           mask with IN_MASK_ADD set.
89
90       -ESTALE
91           The event loop is already terminated.
92
93       -ECHILD
94           The event loop has been created in a different process.
95
96       -EDOM
97           The passed event source is not an inotify process event source.
98

EXAMPLES

100       Example 1. A simple program that uses inotify to monitor one or two
101       directories
102
103           #include <stdio.h>
104           #include <string.h>
105           #include <sys/inotify.h>
106
107           #include <systemd/sd-event.h>
108
109           #define _cleanup_(f) __attribute__((cleanup(f)))
110
111           static int inotify_handler(sd_event_source *source,
112                                      const struct inotify_event *event,
113                                      void *userdata) {
114
115             const char *desc = NULL;
116
117             sd_event_source_get_description(source, &desc);
118
119             if (event->mask & IN_Q_OVERFLOW)
120               printf("inotify-handler <%s>: overflow\n", desc);
121             else if (event->mask & IN_CREATE)
122               printf("inotify-handler <%s>: create on %s\n", desc, event->name);
123             else if (event->mask & IN_DELETE)
124               printf("inotify-handler <%s>: delete on %s\n", desc, event->name);
125             else if (event->mask & IN_MOVED_TO)
126               printf("inotify-handler <%s>: moved-to on %s\n", desc, event->name);
127
128             /* Terminate the program if an "exit" file appears */
129             if ((event->mask & (IN_CREATE|IN_MOVED_TO)) &&
130                 strcmp(event->name, "exit") == 0)
131               sd_event_exit(sd_event_source_get_event(source), 0);
132
133             return 1;
134           }
135
136           int main(int argc, char **argv) {
137             _cleanup_(sd_event_unrefp) sd_event *event = NULL;
138             _cleanup_(sd_event_source_unrefp) sd_event_source *source1 = NULL, *source2 = NULL;
139
140             const char *path1 = argc > 1 ? argv[1] : "/tmp";
141             const char *path2 = argc > 2 ? argv[2] : NULL;
142
143             /* Note: failure handling is omitted for brevity */
144
145             sd_event_default(&event);
146
147             sd_event_add_inotify(event, &source1, path1,
148                                  IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_TO,
149                                  inotify_handler, NULL);
150             if (path2)
151               sd_event_add_inotify(event, &source2, path2,
152                                    IN_CREATE | IN_DELETE | IN_MODIFY | IN_MOVED_TO,
153                                    inotify_handler, NULL);
154
155             sd_event_loop(event);
156
157             return 0;
158           }
159

NOTES

161       These APIs are implemented as a shared library, which can be compiled
162       and linked to with the libsystemd pkg-config(1) file.
163