Fix dmesg printing on Linux

dmesg.c

@@ -31,8 +31,9 @@ main(int argc, char *argv[])
 	n = syslog_read(buf, n);
 	if (n < 0)
 		eprintf("syslog_read:");
-	if (write(STDOUT_FILENO, buf, n) != n)
+	n = syslog_show(STDOUT_FILENO, buf, n);
-		eprintf("write:");
+	if (n < 0)
+		eprintf("syslog_show:");
 	free(buf);
 	return 0;
 }

linux/syslog.c

@@ -1,5 +1,6 @@
 /* See LICENSE file for copyright and license details. */
 #include <sys/klog.h>
+#include <unistd.h>
 #include <stdio.h>
 
 enum {
@@ -18,3 +19,24 @@ syslog_read(void *buf, size_t n)
 {
 	return klogctl(SYSLOG_ACTION_READ_ALL, buf, n);
 }
+
+int
+syslog_show(int fd, const void *buf, size_t n)
+{
+	int last = '\n';
+	const char *p = buf;
+	size_t i;
+
+	for (i = 0; i < n; ) {
+		if (last == '\n' && p[i] == '<') {
+			i += 2;
+			if (i + 1 < n && p[i + 1] == '>')
+				i++;
+		} else {
+			if (write(fd, &p[i], 1) != 1)
+				return -1;
+		}
+		last = p[i++];
+	}
+	return 0;
+}

openbsd/syslog.c

@@ -38,3 +38,9 @@ syslog_read(void *buf, size_t n)
 	memmove(buf, ((struct msgbuf *)buf)->msg_bufc, n);
 	return n;
 }
+
+int
+syslog_show(int fd, const void *buf, size_t n)
+{
+	return write(fd, buf, n);
+}

ubase.h

@@ -11,6 +11,7 @@ int grabmntinfo(struct mntinfo **minfo);
 /* syslog.c */
 int syslog_size(void);
 int syslog_read(void *buf, size_t n);
+int syslog_show(int fd, const void *buf, size_t n);
 
 /* umount.c */
 enum {