'\" t .TH "SD_EVENT_ADD_INOTIFY" "3" "" "systemd 256.8" "sd_event_add_inotify" .\" ----------------------------------------------------------------- .\" * Define some portability stuff .\" ----------------------------------------------------------------- .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .\" http://bugs.debian.org/507673 .\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" ----------------------------------------------------------------- .\" * set default formatting .\" ----------------------------------------------------------------- .\" disable hyphenation .nh .\" disable justification (adjust text to left margin only) .ad l .\" ----------------------------------------------------------------- .\" * MAIN CONTENT STARTS HERE * .\" ----------------------------------------------------------------- .SH "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 .SH "SYNOPSIS" .sp .ft B .nf #include .fi .ft .sp .ft B .nf typedef struct sd_event_source sd_event_source; .fi .ft .HP \w'typedef\ int\ (*sd_event_inotify_handler_t)('u .BI "typedef int (*sd_event_inotify_handler_t)(sd_event_source\ *" "s" ", const\ struct\ inotify_event\ *" "event" ", void\ *" "userdata" ");" .HP \w'int\ sd_event_add_inotify('u .BI "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" ");" .HP \w'int\ sd_event_add_inotify_fd('u .BI "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" ");" .HP \w'int\ sd_event_source_get_inotify_mask('u .BI "int sd_event_source_get_inotify_mask(sd_event_source\ *" "source" ", uint32_t\ *" "ret" ");" .HP \w'int\ sd_event_source_get_inotify_path('u .BI "int sd_event_source_get_inotify_path(sd_event_source\ *" "source" ", const\ char\ **" "ret" ");" .SH "DESCRIPTION" .PP \fBsd_event_add_inotify()\fR adds a new \fBinotify\fR(7) file system inode event source to an event loop\&. The event loop object is specified in the \fIevent\fR parameter, the event source object is returned in the \fIsource\fR parameter\&. The \fIpath\fR parameter specifies the path of the file system inode to watch\&. The \fImask\fR parameter specifies which types of inode events to watch specifically\&. It must contain an OR\-ed combination of \fBIN_ACCESS\fR, \fBIN_ATTRIB\fR, \fBIN_CLOSE_WRITE\fR, \&... flags\&. See \fBinotify\fR(7) for further information\&. .PP The \fIhandler\fR must reference a function to call when the inode changes or \fBNULL\fR\&. The handler function will be passed the \fIuserdata\fR 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 \fIhandler\fR is \fBNULL\fR, a default handler that calls \fBsd_event_exit\fR(3) will be used\&. .PP \fBsd_event_add_inotify_fd()\fR is identical to \fBsd_event_add_inotify()\fR, except that it takes a file descriptor to an inode (possibly an \fBO_PATH\fR one, but any other will do too) instead of a path in the file system\&. .PP 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 \fBIN_MASK_ADD\fR\&. .PP The handler is enabled continuously (\fBSD_EVENT_ON\fR), but this may be changed with \fBsd_event_source_set_enabled\fR(3)\&. Alternatively, the \fBIN_ONESHOT\fR mask flag may be used to request \fBSD_EVENT_ONESHOT\fR mode\&. If the handler function returns a negative error code, it will be disabled after the invocation, even if the \fBSD_EVENT_ON\fR mode was requested before\&. .PP As a special limitation the priority of inotify event sources may only be altered (see \fBsd_event_source_set_priority\fR(3)) in the time between creation of the event source object with \fBsd_event_add_inotify()\fR 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\&. .PP To destroy an event source object use \fBsd_event_source_unref\fR(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\*(Aqs still a reference to it kept, consider disabling it with \fBsd_event_source_set_enabled\fR(3)\&. .PP If the second parameter of \fBsd_event_add_inotify()\fR is passed as \fBNULL\fR 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\&. .PP If the \fIhandler\fR parameter to \fBsd_event_add_inotify()\fR is \fBNULL\fR, and the event source fires, this will be considered a request to exit the event loop\&. In this case, the \fIuserdata\fR parameter, cast to an integer, is passed as the exit code parameter to \fBsd_event_exit\fR(3)\&. .PP \fBsd_event_source_get_inotify_mask()\fR retrieves the configured inotify watch mask of an event source created previously with \fBsd_event_add_inotify()\fR\&. It takes the event source object as the \fIsource\fR parameter and a pointer to a \fBuint32_t\fR variable to return the mask in\&. .PP \fBsd_event_source_get_inotify_path()\fR retrieves the target path of the configured inotify watch of an event source created previously with \fBsd_event_add_inotify()\fR\&. It takes the event source object as the \fIsource\fR parameter and a pointer to a \fBconst char **\fR variable to return the path in\&. The caller must not free the returned path\&. .SH "RETURN VALUE" .PP On success, these functions return 0 or a positive integer\&. On failure, they return a negative errno\-style error code\&. .SS "Errors" .PP Returned errors may indicate the following problems: .PP \fB\-ENOMEM\fR .RS 4 Not enough memory to allocate an object\&. .RE .PP \fB\-EINVAL\fR .RS 4 An invalid argument has been passed\&. This includes specifying a mask with \fBIN_MASK_ADD\fR set\&. .RE .PP \fB\-ESTALE\fR .RS 4 Returned by \fBsd_event_source_add_inotify()\fR or \fBsd_event_source_add_inotify_fd()\fR when the event loop is already terminated\&. Returned by \fBsd_event_source_get_inotify_path()\fR when no active inode data is assigned to the event source, e\&.g\&. when the event source is disabled\&. .RE .PP \fB\-ECHILD\fR .RS 4 The event loop has been created in a different process, library or module instance\&. .RE .PP \fB\-EDOM\fR .RS 4 The passed event source is not an inotify process event source\&. .RE .PP \fB\-EBADF\fR .RS 4 The passed file descriptor is not valid\&. .RE .PP \fB\-ENOSYS\fR .RS 4 \fBsd_event_add_inotify_fd()\fR or \fBsd_event_source_get_inotify_path()\fR was called without /proc/ mounted\&. .RE .SH "EXAMPLES" .PP \fBExample\ \&1.\ \&A simple program that uses inotify to monitor one or two directories\fR .sp .if n \{\ .RS 4 .\} .nf /* SPDX\-License\-Identifier: MIT\-0 */ #include #include #include #include #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\en", desc); else if (event\->mask & IN_CREATE) printf("inotify\-handler <%s>: create on %s\en", desc, event\->name); else if (event\->mask & IN_DELETE) printf("inotify\-handler <%s>: delete on %s\en", desc, event\->name); else if (event\->mask & IN_MOVED_TO) printf("inotify\-handler <%s>: moved\-to on %s\en", 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; } .fi .if n \{\ .RE .\} .SH "NOTES" .PP Functions described here are available as a shared library, which can be compiled against and linked to with the \fBlibsystemd\fR\ \&\fBpkg-config\fR(1) file\&. .PP The code described here uses \fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call \fBsetenv\fR(3) from a parallel thread\&. It is recommended to only do calls to \fBsetenv()\fR from an early phase of the program when no other threads have been started\&. .SH "HISTORY" .PP \fBsd_event_inotify_handler_t()\fR, \fBsd_event_add_inotify()\fR, and \fBsd_event_source_get_inotify_mask()\fR were added in version 239\&. .PP \fBsd_event_add_inotify_fd()\fR was added in version 250\&. .PP \fBsd_event_source_get_inotify_path()\fR was added in version 256\&. .SH "SEE ALSO" .PP \fBsystemd\fR(1), \fBsd-event\fR(3), \fBsd_event_new\fR(3), \fBsd_event_now\fR(3), \fBsd_event_add_io\fR(3), \fBsd_event_add_time\fR(3), \fBsd_event_add_signal\fR(3), \fBsd_event_add_defer\fR(3), \fBsd_event_add_child\fR(3), \fBsd_event_source_set_enabled\fR(3), \fBsd_event_source_set_priority\fR(3), \fBsd_event_source_set_userdata\fR(3), \fBsd_event_source_set_description\fR(3), \fBsd_event_source_set_floating\fR(3), \fBwaitid\fR(2)