all repos — slstatus @ 19f3c8f545237f9db5e994220f3529b192b4bf39

my build of slstatus (tools.suckless.org/slstatus/)

components/OpenBSD/temperature.c

/* See LICENSE file for copyright and license details. */
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/sensors.h>

#include "../../util.h"

const char *
temp(const char *null)
{
	int mib[5];
	size_t size;
	struct sensor temp;

	mib[0] = CTL_HW;
	mib[1] = HW_SENSORS;
	mib[2] = 0; /* cpu0 */
	mib[3] = SENSOR_TEMP;
	mib[4] = 0; /* temp0 */

	size = sizeof(temp);

	if (sysctl(mib, 5, &temp, &size, NULL, 0) == -1) {
		fprintf(stderr, "sysctl 'SENSOR_TEMP': %s\n", strerror(errno));
		return NULL;
	}

	return bprintf("%d", (temp.value - 273150000) / 1000000); /* kelvin to celsius */
}