path: root/upstream/opensuse-tumbleweed/man3/sd_event_add_inotify.3

'\" t
.TH "SD_EVENT_ADD_INOTIFY" "3" "" "systemd 254" "sd_event_add_inotify"
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.SH "NAME"
sd_event_add_inotify, sd_event_add_inotify_fd, sd_event_source_get_inotify_mask, sd_event_inotify_handler_t \- Add an "inotify" file system inode event source to an event loop
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-event\&.h>
.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\ *" "mask" ");"
.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\&.
.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
The event loop is already terminated\&.
.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
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 <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\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 "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)