Add dmesg(1)

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Makefile

@@ -6,11 +6,13 @@ include config.mk
 HDR = util.h arg.h ubase.h
 LIB = \
 	$(OS)/grabmntinfo.o \
+	$(OS)/syslog.o      \
 	util/eprintf.o      \
 	util/estrtol.o
 
 SRC = \
-	df.c
+	df.c                \
+	dmesg.c
 
 OBJ = $(SRC:.c=.o) $(LIB)
 BIN = $(SRC:.c=)

dmesg.c

@@ -0,0 +1,38 @@
+/* See LICENSE file for copyright and license details. */
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "ubase.h"
+#include "util.h"
+
+static void
+usage(void)
+{
+	eprintf("usage: %s\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	int n;
+	char *buf;
+
+	ARGBEGIN {
+	default:
+		usage();
+	} ARGEND;
+
+	n = syslog_size();
+	if (n < 0)
+		eprintf("syslog_size:");
+	buf = malloc(n);
+	if (!buf)
+		eprintf("malloc:");
+	n = syslog_read(buf, n);
+	if (n < 0)
+		eprintf("syslog_read:");
+	if (write(STDOUT_FILENO, buf, n) != n)
+		eprintf("write:");
+	free(buf);
+	return 0;
+}

linux/syslog.c

@@ -0,0 +1,19 @@
+#include <sys/klog.h>
+#include <stdio.h>
+
+enum {
+	SYSLOG_ACTION_READ_ALL = 3,
+	SYSLOG_ACTION_SIZE_BUFFER = 10
+};
+
+int
+syslog_size(void)
+{
+	return klogctl(SYSLOG_ACTION_SIZE_BUFFER, NULL, 0);
+}
+
+int
+syslog_read(void *buf, size_t n)
+{
+	return klogctl(SYSLOG_ACTION_READ_ALL, buf, n);
+}

openbsd/syslog.c

@@ -0,0 +1,39 @@
+#include <sys/param.h>
+#include <sys/sysctl.h>
+#include <sys/msgbuf.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int
+syslog_size(void)
+{
+	int mib[2], msgbufsize;
+	size_t len;
+	int ret;
+
+	mib[0] = CTL_KERN;
+	mib[1] = KERN_MSGBUFSIZE;
+	len = sizeof(msgbufsize);
+	ret = sysctl(mib, 2, &msgbufsize, &len, NULL, 0);
+	if (ret < 0)
+		return ret;
+	msgbufsize += sizeof(struct msgbuf) - 1;
+	return msgbufsize;
+}
+
+int
+syslog_read(void *buf, size_t n)
+{
+	int mib[2];
+	int ret;
+
+	memset(buf, 0, n);
+	mib[0] = CTL_KERN;
+	mib[1] = KERN_MSGBUF;
+	ret = sysctl(mib, 2, buf, &n, NULL, 0);
+	if (ret < 0)
+		return ret;
+	memmove(buf, ((struct msgbuf *)buf)->msg_bufc, n);
+	return n;
+}

ubase.h

@@ -5,3 +5,7 @@ struct mntinfo {
 };
 
 int grabmntinfo(struct mntinfo **minfo);
+
+/* syslog.c */
+int syslog_size(void);
+int syslog_read(void *buf, size_t n);