initial commit

.gitignore

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+/a.out
+/measurer

Makefile

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+CC = gcc
+CFLAGS = -Wall -g
+SOURCE = main.c
+TARGET = measurer
+
+# Default target
+all: $(TARGET)
+
+# Rule to build the executable
+$(TARGET): $(SOURCE)
+	$(CC) $(CFLAGS) -o $@ $<
+
+# Rule to clean up object files and the executable
+clean:
+	rm -f $(TARGET) *.o
+
+# Phony targets
+.PHONY: all clean

README.md

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+a lightweight script that logs the most important stuff about the raspberry pi
+
+# most important stuff what
+- cpu temperature
+
+# warning
+CPU temperature is read from `/sys/class/thermal/thermal_zone0/temp` but that should work on every Linux computer \
+Ambient temperature is read from `/sys/bus/w1/devices` so you must have 1wire enabled, if you don't have that set `SENSOR` to `0`
+
+# compilation
+`make` or `gcc main.c -o measurer` \
+Should throw no warnings
+
+# why
+like heavy ahh like databases grafana etc go away you're a performance monitor why'd you reduce performance

main.c

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+#include <limits.h>
+#include <stdio.h>
+#include <dirent.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <time.h>
+
+#define SENSOR 1
+
+int read_temperature(char *filename) {
+    FILE *fp;
+    fp = fopen(filename, "r");
+
+    if (fp == NULL) {
+        fprintf(stderr, "Error opening file %s: %s\n", filename, strerror(errno)); // instead of perror
+        return INT_MIN;
+    }
+
+    char buffer[6]; // because the file returns 5 digits + null terminator
+
+    if (fgets(buffer, sizeof(buffer), fp) == NULL) {
+        fprintf(stderr, "Error reading from %s: %s\n", filename, strerror(errno));
+        fclose(fp);
+        return INT_MIN;
+    }
+
+    fclose(fp);
+
+    int temperature = strtol(buffer, NULL, 10);
+    return temperature;
+}
+
+int detect_ds18b20(char *w1_id) {
+    DIR *d;
+    struct dirent *dir;
+    d = opendir("/sys/bus/w1/devices");
+    
+    bool success = false;
+
+    if (d) {
+        while ((dir = readdir(d)) != NULL) {
+            strcpy(w1_id, dir->d_name);
+            if (strncmp("28", w1_id, 2) == 0) {
+                success = true;
+            }
+        }
+        closedir(d);
+    } else {
+        perror("Unable to open w1 directory");
+    }
+
+    if (success) return 0;
+    return 1;
+}
+
+
+int read_cpu_temperature() {
+    return read_temperature("/sys/class/thermal/thermal_zone0/temp");
+}
+
+int read_w1_temperature(char *w1_id) {
+    char *path;
+    if (asprintf(&path, "/sys/bus/w1/devices/%s/temperature", w1_id) == -1) {
+        fprintf(stderr, "Unable to get path for %s: %s\n", w1_id, strerror(errno));
+        return INT_MIN;
+    }
+    return read_temperature(path);
+}
+
+int main(int argc, char *argv[]) {
+    if (argc == 0) {
+        printf("Filename required\n");
+        return 1;
+    }
+
+    time_t now = time(0);
+    char *line;
+
+    int cpu_temperature;
+    if ((cpu_temperature = read_cpu_temperature()) == INT_MIN) {
+        perror("Failed to read cpu temperature");
+        return 1;
+    }
+    
+    if (SENSOR) {
+        char w1_id[16];
+        if ((detect_ds18b20(w1_id)) == 1)
+            return 1;
+        printf("Using sensor: %s\n", w1_id);
+
+        int env_temperature;
+        if ((env_temperature = read_w1_temperature(w1_id)) == INT_MIN) {
+            perror("Failed to read env temperature");
+            return 1;
+        }
+
+        asprintf(&line, "%ld,%d,%d\n", now, cpu_temperature, env_temperature);
+        printf("timestamp,cpu_temp,env_temp\n%s", line);
+    } else {
+        asprintf(&line, "%ld,%d\n", now, cpu_temperature);
+        printf("timestamp,cpu_temp\n%s", line);
+    }
+
+
+    FILE *fp;
+    fp = fopen(argv[0], "a");
+
+    if (fp == NULL) {
+        printf("Error opening output file");
+        return 1;
+    }
+
+    if (fprintf(fp, line) != 0) {
+        perror("Error writing to output file");
+        fclose(fp);
+        return 1;
+    }
+    fclose(fp);
+}