From: Eitan Adler <lists@eitanadler.com>
Date: Fri, 10 May 2013 18:24:39 +0000 (-0400)
Subject: Add option 'dmesg -c' which clears the kernel buffer after it is printed.
X-Git-Tag: v3.7.0~1126
X-Git-Url: https://gitweb.dragonflybsd.org/~tuxillo/dragonfly.git/commitdiff_plain/f5c1f6e0209e27d15d137c23e552ef830b9c6c7f

Add option 'dmesg -c' which clears the kernel buffer after it is printed.

Tested by:	swildner
---

diff --git a/sbin/dmesg/dmesg.8 b/sbin/dmesg/dmesg.8
index c17bf19da7..b90d011e44 100644
--- a/sbin/dmesg/dmesg.8
+++ b/sbin/dmesg/dmesg.8
@@ -31,9 +31,8 @@
 .\"
 .\"     @(#)dmesg.8	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD: src/sbin/dmesg/dmesg.8,v 1.5.2.5 2002/08/21 18:58:17 trhodes Exp $
-.\" $DragonFly: src/sbin/dmesg/dmesg.8,v 1.2 2003/06/17 04:27:32 dillon Exp $
 .\"
-.Dd June 5, 1993
+.Dd May 10, 2013
 .Dt DMESG 8
 .Os
 .Sh NAME
@@ -42,6 +41,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl a
+.Op Fl c
 .Op Fl M Ar core
 .Op Fl N Ar system
 .Sh DESCRIPTION
@@ -67,6 +67,8 @@ Show all data in the message buffer.
 This includes any syslog records and
 .Pa /dev/console
 output.
+.It Fl c
+Clear the kernel buffer after printing.
 .It Fl M
 Extract values associated with the name list from the specified core
 instead of the default
diff --git a/sbin/dmesg/dmesg.c b/sbin/dmesg/dmesg.c
index e781570ee9..e15529e974 100644
--- a/sbin/dmesg/dmesg.c
+++ b/sbin/dmesg/dmesg.c
@@ -29,7 +29,6 @@
  * @(#) Copyright (c) 1991, 1993 The Regents of the University of California.  All rights reserved.
  * @(#)dmesg.c	8.1 (Berkeley) 6/5/93
  * $FreeBSD: src/sbin/dmesg/dmesg.c,v 1.11.2.3 2001/08/08 22:32:15 obrien Exp $
- * $DragonFly: src/sbin/dmesg/dmesg.c,v 1.7 2005/01/14 06:38:41 cpressey Exp $
  */
 
 #include <sys/types.h>
@@ -67,16 +66,20 @@ main(int argc, char **argv)
 	kvm_t *kd;
 	char buf[5];
 	int all = 0;
+	int clear = 0;
 	int pri = 0;
 	size_t buflen, bufpos;
 
 	setlocale(LC_CTYPE, "");
 	memf = nlistf = NULL;
-	while ((ch = getopt(argc, argv, "aM:N:")) != -1)
+	while ((ch = getopt(argc, argv, "acM:N:")) != -1)
 		switch(ch) {
 		case 'a':
 			all++;
 			break;
+		case 'c':
+			clear = 1;
+			break;
 		case 'M':
 			memf = optarg;
 			break;
@@ -173,12 +176,15 @@ main(int argc, char **argv)
 	} while (++p != ep);
 	if (!newl)
 		putchar('\n');
+	if (clear)
+		if (sysctlbyname("kern.msgbuf_clear", NULL, NULL, &clear, sizeof(int)) != 0)
+			err(1, "sysctl kern.msgbuf_clear");
 	exit(0);
 }
 
 void
 usage(void)
 {
-	fprintf(stderr, "usage: dmesg [-a] [-M core] [-N system]\n");
+	fprintf(stderr, "usage: dmesg [-ac] [-M core] [-N system]\n");
 	exit(1);
 }