.\"	$OpenBSD: mdoc.template,v 1.9 2004/07/02 10:36:57 jmc Exp $
.\"
.Dd July 24, 2007
.Dt pnotify 3
.Os
.Sh NAME
.Nm pnotify
.Nd monitor filesystem events
.Sh SYNOPSIS
.In pnotify.h
.Pp
.Fd int pnotify_init(struct pnotify_cb *ctl);
.Fd int pnotify_add_watch(struct pnotify_cb *ctl, const char *pathname, int mask);
.Fd int pnotify_rm_watch(struct pnotify_cb *ctl, int wd);
.Fd int pnotify_get_event(struct pnotify_event *evt, struct pnotify_cb *ctl);
.Fd int pnotify_free(struct pnotify_cb *ctl);
.Pp
.Bd -literal
struct pnotify_event {
        int       wd;
        int       mask;
        char      name[NAME_MAX + 1];
};
.Ed

.Sh DESCRIPTION
The
.Nm
library provides a portable way to monitor filesystem events. It closely resembles
the inotify(7) kernel subsystem in Linux, but is implemented as a userspace library
to support other kernel mechanisms such as kqueue(4).
.Pp
.Fn pnotify_init
initializes a pnotify control block.  This structure contains the current state of events and watches, and must be initialized before it can be used.
.Pp
.Fn pnotify_add_watch
adds a watch for a given file or directory. The mask parameter is composed of one
or more bitflags from the following list of events:
.Bl -column "Flag" "Meaning" -offset indent
.It Sy PN_ACCESS Ta "The access time (atime) has been modified."
.It Sy PN_CREATE Ta "A file was created in the directory."
.It Sy PN_DELETE Ta "The file was deleted."
.It Sy PN_MODIFY Ta "The modification time (mtime) has been modified."
.El
.Pp
When calling
.Fn pnotify_add_watch
the following flags may also be used:
.Bl -column "Flag" "Meaning" -offset indent
.It Sy PN_ALL_EVENTS Ta "Monitor all events."
.It Sy PN_ONESHOT Ta "Delete the watch after an event occurs."
.El

.Fn pnotify_rm_watch
removes a watch from the watchlist.

.Fn pnotify_get_event
blocks until an event occurs, and fills the pnotify_event structure with information
about the event.  If an error occurs in the underlying kernel event queue, an
event is returned with the PN_ERROR flag set.

.Fn pnotify_free
frees all of the memory associated with a control block and closes the kernel event
descriptor.

.Sh RETURN VALUES
.Fn pnotify_add_watch
returns a positive integer that represents a unique watch descriptor, or -1 if an error occurs.
.Pp
All other functions return zero if successful, or -1 if an error occurs.
.Sh EXAMPLES

The following example creates a watch on the /tmp directory and prints the 
names of files that are created or deleted within the directory.
.Bd -literal
struct pnotify_cb ctl;
struct pnotify_event evt;

pnotify_init(&ctl);
pnotify_add_watch(&ctl, "/tmp", PN_ALL_EVENTS);
while (pnotify_get_event(&evt, &ctl, NULL) == 0) {
	if (evt.mask & PN_CREATE) 
		printf("file created: %s", evt.name);
	if (evt.mask & PN_DELETE) 
		printf("file deleted: %s", evt.name);
	if (evt.mask & PN_ERROR) {
		printf("an error occurred");
		break;
	}
}
pnotify_free(&ctl);
.Ed

.Sh THREADSAFETY
All
.Nm
functions are fully reentrant and may be used in multithreaded programs. 
A single
.Nm
control block (struct pnotify_cb) should not be shared by multiple threads
unless it is protected by a mutex.

.Sh SEE ALSO
.Xr kqueue 4
.Xr inotify 7

.\" .Sh STANDARDS
.Sh HISTORY
pnotify was first released on July 25th, 2007 with support for inotify and kqueue.
.Sh AUTHORS
Mark Heily <devel@heily.com>
.\" .Sh CAVEATS
.\" .Sh BUGS
.\"kqueue(4) support is buggy and only works properly with PN_CREATE events.