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Provide an example to the kqueue man page, showing

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a basic usage example.  Although it is an
untypical example for the use of kqueue, it is
better than nothing and should get people started.

PR:			196844
Submitted by:		fernando.apesteguia@gmail.com
Reviewed by:		kib
Approved by:		kib
MFC after:		5 days
Differential Revision:	https://reviews.freebsd.org/D6082
This commit is contained in:
Benedict Reuschling 2016-05-01 18:09:34 +00:00
parent 93a0b67496
commit 8c231786f0
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=298893
1 changed files with 52 additions and 1 deletions
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53
lib/libc/sys/kqueue.2
View File

@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd August 4, 2015
.Dd May 1, 2016
.Dt KQUEUE 2
.Os
.Sh NAME
@ -603,6 +603,57 @@ will be set to indicate the error condition.
If the time limit expires, then
.Fn kevent
returns 0.
.Sh EXAMPLES
.Bd -literal -compact
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int
main(int argc, char **argv)
{
struct kevent event; /* Event we want to monitor */
struct kevent tevent; /* Event triggered */
int kq, fd, ret;
if (argc != 2)
err(EXIT_FAILURE, "Usage: %s path\en", argv[0]);
fd = open(argv[1], O_RDONLY);
if (fd == -1)
err(EXIT_FAILURE, "Failed to open '%s'", argv[1]);
/* Create kqueue. */
kq = kqueue();
if (kq == -1)
err(EXIT_FAILURE, "kqueue() failed");
/* Initialize kevent structure. */
EV_SET(&event, fd, EVFILT_VNODE, EV_ADD | EV_CLEAR, NOTE_WRITE,
0, NULL);
/* Attach event to the kqueue. */
ret = kevent(kq, &event, 1, NULL, 0, NULL);
if (ret == -1)
err(EXIT_FAILURE, "kevent register");
if (event.flags & EV_ERROR)
errx(EXIT_FAILURE, "Event error: %s", strerror(event.data));
for (;;) {
/* Sleep until something happens. */
ret = kevent(kq, NULL, 0, &tevent, 1, NULL);
if (ret == -1) {
err(EXIT_FAILURE, "kevent wait");
} else if (ret > 0) {
printf("Something was written in '%s'\en", argv[1]);
}
}
}
.Ed
.Sh ERRORS
The
.Fn kqueue