Index: usr.bin/time/time.1
===================================================================
--- usr.bin/time/time.1
+++ usr.bin/time/time.1
@@ -28,7 +28,7 @@
 .\"     @(#)time.1	8.1 (Berkeley) 6/6/93
 .\" $FreeBSD$
 .\"
-.Dd May 14, 2006
+.Dd Jan 24, 2018
 .Dt TIME 1
 .Os
 .Sh NAME
@@ -37,7 +37,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl al
-.Op Fl h | Fl p
+.Op Fl hm | Fl p
 .Op Fl o Ar file
 .Ar utility Op Ar argument ...
 .Sh DESCRIPTION
@@ -74,6 +74,10 @@
 The contents of the
 .Em rusage
 structure are printed as well.
+.It Fl m
+Report elapsed time time using the monotonic clock, rather than the realtime clock.
+Using this option will give more reliable measurements when measuring short
+intervals of time.
 .It Fl o Ar file
 Write the output to
 .Ar file
Index: usr.bin/time/time.c
===================================================================
--- usr.bin/time/time.c
+++ usr.bin/time/time.c
@@ -62,6 +62,7 @@
 #include <unistd.h>
 
 static int getstathz(void);
+static void gettime(struct timespec *, int);
 static void humantime(FILE *, long, long);
 static void showtime(FILE *, struct timespec *, struct timespec *,
     struct rusage *);
@@ -76,7 +77,7 @@
 int
 main(int argc, char **argv)
 {
-	int aflag, ch, lflag, status;
+	int aflag, ch, lflag, mflag, status;
 	int exitonsig;
 	pid_t pid;
 	struct rlimit rl;
@@ -88,8 +89,8 @@
 	(void) setlocale(LC_NUMERIC, "");
 	decimal_point = localeconv()->decimal_point[0];
 
-	aflag = hflag = lflag = pflag = 0;
-	while ((ch = getopt(argc, argv, "ahlo:p")) != -1)
+	aflag = hflag = lflag = mflag = pflag = 0;
+	while ((ch = getopt(argc, argv, "ahlo:mp")) != -1)
 		switch((char)ch) {
 		case 'a':
 			aflag = 1;
@@ -100,6 +101,9 @@
 		case 'l':
 			lflag = 1;
 			break;
+		case 'm':
+			mflag = 1;
+			break;
 		case 'o':
 			ofn = optarg;
 			break;
@@ -111,6 +115,9 @@
 			usage();
 		}
 
+	if (mflag && pflag)
+		errx(2, "monotonic output and posix output are incompatible");
+
 	if (!(argc -= optind))
 		exit(0);
 	argv += optind;
@@ -121,8 +128,7 @@
 		setvbuf(out, (char *)NULL, _IONBF, (size_t)0);
 	}
 
-	if (clock_gettime(CLOCK_REALTIME, &before_ts))
-		err(1, "clock_gettime");
+	gettime(&before_ts, mflag);
 	switch(pid = fork()) {
 	case -1:			/* error */
 		err(1, "time");
@@ -141,14 +147,12 @@
 	while (wait4(pid, &status, 0, &ru) != pid) {
 		if (siginfo_recvd) {
 			siginfo_recvd = 0;
-			if (clock_gettime(CLOCK_REALTIME, &after))
-				err(1, "clock_gettime");
+			gettime(&after, mflag);
 			getrusage(RUSAGE_CHILDREN, &ru);
 			showtime(stdout, &before_ts, &after, &ru);
 		}
 	}
-	if (clock_gettime(CLOCK_REALTIME, &after))
-		err(1, "clock_gettime");
+	gettime(&after, mflag);
 	if ( ! WIFEXITED(status))
 		warnx("command terminated abnormally");
 	exitonsig = WIFSIGNALED(status) ? WTERMSIG(status) : 0;
@@ -238,6 +242,15 @@
 	if (sysctl(mib, 2, &clockrate, &size, NULL, 0) == -1)
 		err(1, "sysctl kern.clockrate");
 	return clockrate.stathz;
+}
+
+static void
+gettime(struct timespec *ts, int monotonic)
+{
+	clockid_t clock = monotonic ? CLOCK_MONOTONIC : CLOCK_REALTIME;
+
+	if (clock_gettime(clock, ts))
+		err(1, "clock_gettime");
 }
 
 static void