ts: Introduce '-m' option to use CLOCK_MONOTONIC

The new '-m' option will retrieve the monotonic clock rather than the
realtime clock.

Sometimes it is required that the timer being used not change even when
the user updates the system time. The monotonic clock guarantees a
monotonically increasing time value which may not be adjusted.

Signed-off-by: Ben Leinweber <bleinweb@gmail.com>

1 files changed, 20 insertions, 4 deletions

diff --git a/ts b/ts
index 63baf18..7f6ff85 100755
--- a/ts
+++ b/ts
@@ -56,8 +56,9 @@ $|=1;
 my $rel=0;
 my $inc=0;
 my $sincestart=0;
+my $mono=0;
 use Getopt::Long;
-GetOptions("r" => \$rel, "i" => \$inc, "s" => \$sincestart) || die "usage: ts [-r] [-i | -s] [format]\n";
+GetOptions("r" => \$rel, "i" => \$inc, "s" => \$sincestart, "m" => \$mono) || die "usage: ts [-r] [-i | -s] [format]\n";
 
 if ($rel) {
 	eval q{
@@ -77,15 +78,20 @@ $format=shift if @ARGV;
 
 # For subsecond resolution, Time::HiRes is needed.
 my $hires=0;
-if ($format=~/\%\.[Ss]/) {
+if ($format=~/\%\.[Ss]/ || $mono) {
 	require Time::HiRes;
+	use Time::HiRes qw(CLOCK_MONOTONIC);
 	$hires=1;
 }
 
 my $lastseconds = 0;
 my $lastmicroseconds = 0;
 
-if ($hires) {
+if ($mono) {
+	my $raw_time = Time::HiRes::clock_gettime(CLOCK_MONOTONIC);
+	$lastseconds = int($raw_time);
+	$lastmicroseconds = int(1000000 * ($raw_time - $lastseconds));
+} elsif ($hires) {
 	($lastseconds, $lastmicroseconds) = Time::HiRes::gettimeofday();
 } else {
 	$lastseconds = time;
@@ -96,7 +102,17 @@ while (<>) {
 	if (! $rel) {
 		if ($hires) {
 			my $f=$format;
-			my ($seconds, $microseconds) = Time::HiRes::gettimeofday();
+            my $seconds;
+			my $microseconds;
+			if ($mono) {
+				my $raw_time =
+					Time::HiRes::clock_gettime(CLOCK_MONOTONIC);
+				$seconds = int($raw_time);
+				$microseconds = int(1000000 * ($raw_time - $seconds));
+			} else {
+				($seconds, $microseconds) = Time::HiRes::gettimeofday();
+			}
+
 			if ($inc || $sincestart) {
 				my $deltaseconds = $seconds - $lastseconds;
 				my $deltamicroseconds = $microseconds - $lastmicroseconds;