cmd-timer

commit: 064c1783a7009c4331de2dadebad2d89f069898f
parent ccbdca4a51d50b4d7c24eced5c883e6c4e310fc7
Author: Haelwenn (lanodan) Monnier <contact@hacktivis.me>
Date:   Sun, 17 Aug 2025 17:58:03 +0200

Add -c option to specify which clockid to use

Diffstat:
M
timer.1
28
+++++++++++++++++++++++++++-
M
timer.c
57
++++++++++++++++++++++++++++++++++++++++++++++++++++++---

2 files changed, 81 insertions(+), 4 deletions(-)
diff --git a/timer.1 b/timer.1
@@ -9,6 +9,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl w
+.Op Fl c Ar clockid
 .Ar interval
 .Ar command
 .Op Ar arguments...
@@ -24,7 +25,7 @@ The
 .Ar interval
 argument is a string containing non-negative decimal numbers including floats,
 terminated by suffixes:
-s for seconds, m for minutes, h for hours, d for days.
+s\ for\ seconds, m\ for\ minutes, h\ for\ hours, d\ for\ days.
 .br
 If the final number doesn't have a suffix, seconds are assumed.
 Longer durations are taken as out of scope.
@@ -37,6 +38,31 @@ exits with the same status,
 allowing to use service supervision to track failures.
 .Sh OPTIONS
 .Bl -tag -width Ds
+.It Fl c Ar clockid
+Set the clock to be used for the timer.
+The
+.Ar clockid
+argument can be set to one of the following shortcodes:
+.Bl -tag -compact -width __
+.It r
+CLOCK_REALTIME (default)
+.It m
+CLOCK_MONOTONIC
+.It b
+CLOCK_BOOTTIME
+.It ra
+CLOCK_REALTIME_ALARM
+.It ba
+CLOCK_BOOTTIME_ALARM
+.It t
+CLOCK_TAI
+.El
+.Pp
+See
+.Xr timer_create 3
+for the behavior of each clock.
+Note that only CLOCK_REALTIME and CLOCK_MONOTONIC are portably
+defined in POSIX.1-2024.
 .It Fl w
 Wait for
 .Ar interval
diff --git a/timer.c b/timer.c
@@ -21,6 +21,12 @@ static char **args;
 
 const char *argv0 = "timer";
 
+struct clock_name
+{
+	const char *name;
+	clockid_t clock;
+};
+
 static void
 sig_timer(int sig)
 {
@@ -48,7 +54,7 @@ sig_chld(int sig)
 static void
 bad_usage()
 {
-	fputs("Usage: timer [-w] <interval> <command> [arguments...]\n", stderr);
+	fputs("Usage: timer [-w] [-c clock_id] <interval> <command> [arguments...]\n", stderr);
 	exit(1);
 }
 
@@ -63,16 +69,61 @@ int
 main(int argc, char *argv[])
 {
 	bool opt_w = false;
+	clockid_t clockid = CLOCK_REALTIME;
 
-	for(char c = -1; (c = getopt(argc, argv, ":w")) != -1;)
+	for(char c = -1; (c = getopt(argc, argv, ":c:w")) != -1;)
 	{
 		switch(c)
 		{
+		case 'c':
+		{
+			// clang-format off
+			static struct clock_name clock_names[] = {
+				{"m", CLOCK_MONOTONIC},
+				{"r", CLOCK_REALTIME},
+#ifdef CLOCK_BOOTTIME
+				{"b", CLOCK_BOOTTIME},
+#endif
+#ifdef CLOCK_REALTIME_ALARM
+				{"ra", CLOCK_REALTIME_ALARM},
+#endif
+#ifdef CLOCK_BOOTTIME_ALARM
+				{"ba", CLOCK_BOOTTIME_ALARM},
+#endif
+#ifdef CLOCK_TAI
+				{"t", CLOCK_TAI},
+#endif
+			};
+			static size_t clock_len = sizeof(clock_names)/sizeof(*clock_names);
+			// clang-format on
+
+			size_t i = 0;
+			for(; i < clock_len; i++)
+			{
+				if(strcmp(optarg, clock_names[i].name) == 0)
+				{
+					clockid = clock_names[i].clock;
+					break;
+				}
+			}
+
+			if(i == clock_len)
+			{
+				fprintf(stderr, "timer: error: Unknown clock '%s' given to -c\n", optarg);
+				bad_usage();
+			}
+			break;
+		}
 		case 'w':
 			opt_w = true;
 			break;
+		case ':':
+			fprintf(stderr, "%s: error: Missing operand for option: '-%c'\n", argv0, optopt);
+			bad_usage();
+			break;
 		default:
 			fprintf(stderr, "timer: error: Unhandled option -%c\n", optopt);
+			bad_usage();
 			return 1;
 		}
 	}
@@ -129,7 +180,7 @@ main(int argc, char *argv[])
 	timer_se.sigev_notify = SIGEV_SIGNAL;
 
 	timer_t timer;
-	if(timer_create(0, &timer_se, &timer) != 0)
+	if(timer_create(clockid, &timer_se, &timer) != 0)
 	{
 		fprintf(stderr, "timer: error: Failed creating timer: %s\n", strerror(errno));
 		return 1;