diff --git a/sbin/dmesg/dmesg.8 b/sbin/dmesg/dmesg.8 index 9d05e6c70b75..b5004f5fd40b 100644 --- a/sbin/dmesg/dmesg.8 +++ b/sbin/dmesg/dmesg.8 @@ -36,7 +36,7 @@ .Nd "display the system message buffer" .Sh SYNOPSIS .Nm -.Op Fl a +.Op Fl ac .Op Fl M Ar core Op Fl N Ar system .Sh DESCRIPTION The @@ -59,6 +59,8 @@ 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. .It Fl N diff --git a/sbin/dmesg/dmesg.c b/sbin/dmesg/dmesg.c index 002732cc479c..1d548a7bef3c 100644 --- a/sbin/dmesg/dmesg.c +++ b/sbin/dmesg/dmesg.c @@ -54,6 +54,7 @@ __FBSDID("$FreeBSD$"); #include #include #include +#include #include #include #include @@ -79,15 +80,20 @@ main(int argc, char *argv[]) kvm_t *kd; size_t buflen, bufpos; long pri; - int all, ch; + int ch, clear; + bool all; - all = 0; + all = false; + clear = false; (void) 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++; + all = true; + break; + case 'c': + clear = true; break; case 'M': memf = optarg; @@ -190,12 +196,16 @@ main(int argc, char *argv[]) (void)strvisx(visbp, p, nextp - p, 0); (void)printf("%s", visbp); } + if (clear) + if (sysctlbyname("kern.msgbuf_clear", NULL, NULL, &clear, sizeof(int))) + err(1, "sysctl kern.msgbuf_clear"); + exit(0); } void usage(void) { - (void)fprintf(stderr, "usage: dmesg [-a] [-M core [-N system]]\n"); + fprintf(stderr, "usage: dmesg [-ac] [-M core [-N system]]\n"); exit(1); }