diff --git a/.gitignore b/.gitignore
index d09ccdd..4c98fb0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 *.o
 catsit
+catsit-timer
 catsit-watch
 catsit.conf
 catsitd
diff --git a/Makefile b/Makefile
index 573c1f3..2f52b2f 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,7 @@ RC_SCRIPT = ${UNAME}/catsitd
 
 -include config.mk
 
-BINS = catsit-watch
+BINS = catsit-timer catsit-watch
 SBINS = catsit catsitd
 MAN1 = ${BINS:=.1}
 MAN5 = catsit.conf.5
diff --git a/catsit-timer.1 b/catsit-timer.1
new file mode 100644
index 0000000..9ad8956
--- /dev/null
+++ b/catsit-timer.1
@@ -0,0 +1,62 @@
+.Dd February 25, 2021
+.Dt CATSIT-TIMER 1
+.Os
+.
+.Sh NAME
+.Nm catsit-timer
+.Nd run command at interval
+.
+.Sh SYNOPSIS
+.Nm
+.Ar interval
+.Ar command ...
+.
+.Sh DESCRIPTION
+The
+.Nm
+utility runs a command
+at an interval.
+The command is run once immediately,
+then again every
+.Ar interval
+after waiting for the command to exit
+each time.
+The
+.Nm
+utility is not appropriate
+for scheduling commands
+to run at specific times.
+.
+.Pp
+The format of the
+.Ar interval
+specifier is a series of integers
+followed by units:
+.Cm s
+for seconds,
+.Cm m
+for minutes
+and
+.Cm h
+for hours.
+An integer with no unit
+is assumed to be in seconds.
+The
+.Ar interval
+is the sum of each
+integer-unit pair.
+For example,
+.Cm 1m30s
+is equivalent to
+.Cm 90s .
+.
+.Sh EXIT STATUS
+If the command exits non-zero,
+.Nm
+exits with the same status.
+.
+.Sh SEE ALSO
+.Xr catsitd 8
+.
+.Sh AUTHORS
+.An June Bug Aq Mt june@causal.agency
diff --git a/catsit-timer.c b/catsit-timer.c
new file mode 100644
index 0000000..2869311
--- /dev/null
+++ b/catsit-timer.c
@@ -0,0 +1,70 @@
+/* Copyright (C) 2021  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+static void run(char *argv[]) {
+	pid_t pid = fork();
+	if (pid < 0) err(EX_OSERR, "fork");
+	if (!pid) {
+		execvp(argv[0], argv);
+		err(126, "%s", argv[0]);
+	}
+
+	int status;
+	pid = wait(&status);
+	if (pid < 0) err(EX_OSERR, "wait");
+	if (WIFEXITED(status)) {
+		status = WEXITSTATUS(status);
+		if (status) exit(status);
+	} else {
+		exit(status);
+	}
+}
+
+int main(int argc, char *argv[]) {
+	if (argc < 2) errx(EX_USAGE, "interval required");
+	if (argc < 3) errx(EX_USAGE, "command required");
+
+	unsigned interval = 0;
+	char *spec = argv[1];
+	while (*spec) {
+		unsigned num = strtoul(spec, &spec, 10);
+		switch (*spec) {
+			break; case '\0': interval += num;
+			break; case 's': spec++; interval += num;
+			break; case 'm': spec++; interval += 60 * num;
+			break; case 'h': spec++; interval += 60 * 60 * num;
+			break; default: errx(EX_USAGE, "invalid interval unit %c", *spec);
+		}
+	}
+	if (!interval) errx(EX_USAGE, "invalid zero interval");
+
+#ifdef __OpenBSD__
+	int error = pledge("stdio proc exec", NULL);
+	if (error) err(EX_OSERR, "pledge");
+#endif
+
+	for (;;) {
+		run(&argv[2]);
+		sleep(interval);
+	}
+}
diff --git a/catsit.conf.5 b/catsit.conf.5
index 7469e74..ccac76d 100644
--- a/catsit.conf.5
+++ b/catsit.conf.5
@@ -80,6 +80,7 @@ pounce/tilde	pounce ${0#*/}.conf
 .Ed
 .
 .Sh SEE ALSO
+.Xr catsit-timer 1 ,
 .Xr catsit-watch 1 ,
 .Xr catsitd 8
 .