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Add useful example program from

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http://mail-index.netbsd.org/tech-kern/2009/09/01/msg006020.html
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elad 2009-09-01 22:01:48 +00:00
parent f6062bf27a
commit 8fbf70d4eb
1 changed files with 72 additions and 2 deletions
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74
lib/libc/sys/kqueue.2
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@ -1,4 +1,4 @@
.\" $NetBSD: kqueue.2,v 1.22 2009/03/12 10:16:37 wiz Exp $
.\" $NetBSD: kqueue.2,v 1.23 2009/09/01 22:01:48 elad Exp $
.\"
.\" Copyright (c) 2000 Jonathan Lemon
.\" All rights reserved.
@ -32,7 +32,7 @@
.\"
.\" $FreeBSD: src/lib/libc/sys/kqueue.2,v 1.22 2001/06/27 19:55:57 dd Exp $
.\"
.Dd February 4, 2003
.Dd September 1, 2009
.Dt KQUEUE 2
.Os
.Sh NAME
@ -478,6 +478,76 @@ will be set to indicate the error condition.
If the time limit expires, then
.Fn kevent
returns 0.
.Sh EXAMPLES
The following example program monitors a file (provided to it as the first
argument) and prints information about some common events it receives
notifications for:
.Bd -literal -offset indent
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <err.h>
int
main(int argc, char *argv[])
{
int fd, kq, nev;
struct kevent ev, ch;
static const struct timespec tout = { 1, 0 };
if ((fd = open(argv[1], O_RDONLY)) == -1)
err(1, "Cannot open `%s'", argv[1]);
if ((kq = kqueue()) == -1)
err(1, "Cannot create kqueue");
EV_SET(&ch, fd, EVFILT_VNODE, EV_ADD | EV_ENABLE | EV_CLEAR,
NOTE_DELETE|NOTE_WRITE|NOTE_EXTEND|NOTE_ATTRIB|NOTE_LINK|
NOTE_RENAME|NOTE_REVOKE, 0, 0);
for (;;) {
nev = kevent(kq, &ch, 1, &ev, 1, &tout);
if (nev == -1)
err(1, "kevent");
if (nev == 0)
continue;
if (ev.fflags & NOTE_DELETE) {
printf("deleted ");
ev.fflags &= ~NOTE_DELETE;
}
if (ev.fflags & NOTE_WRITE) {
printf("written ");
ev.fflags &= ~NOTE_WRITE;
}
if (ev.fflags & NOTE_EXTEND) {
printf("extended ");
ev.fflags &= ~NOTE_EXTEND;
}
if (ev.fflags & NOTE_ATTRIB) {
printf("chmod/chown ");
ev.fflags &= ~NOTE_ATTRIB;
}
if (ev.fflags & NOTE_LINK) {
printf("hardlinked ");
ev.fflags &= ~NOTE_LINK;
}
if (ev.fflags & NOTE_RENAME) {
printf("renamed ");
ev.fflags &= ~NOTE_RENAME;
}
if (ev.fflags & NOTE_REVOKE) {
printf("revoked ");
ev.fflags &= ~NOTE_REVOKE;
}
printf("\\n");
if (ev.fflags)
warnx("unknown event 0x%x\\n", ev.fflags);
}
}
.Ed
.Sh ERRORS
The
.Fn kqueue