simplest local weather proxy over SHM

Daemons/weather_proxy/weather_client.c

@@ -0,0 +1,57 @@
+#include "weather_data.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <semaphore.h>
+#include <unistd.h>
+
+#define SHM_NAME "/weather_shm"
+#define SEM_NAME "/weather_sem"
+
+int get_weather_data(weather_data_t *data) {
+    int shm_fd;
+    sem_t *sem;
+    weather_data_t *shared_data;
+    int ret = 0;
+
+    shm_fd = shm_open(SHM_NAME, O_RDONLY, 0600);
+    if (shm_fd == -1) {
+        perror("shm_open");
+        return -1;
+    }
+
+    shared_data = mmap(NULL, sizeof(weather_data_t), PROT_READ, MAP_SHARED, shm_fd, 0);
+    if (shared_data == MAP_FAILED) {
+        perror("mmap");
+        close(shm_fd);
+        return -1;
+    }
+
+    sem = sem_open(SEM_NAME, 0);
+    if (sem == SEM_FAILED) {
+        perror("sem_open");
+        munmap(shared_data, sizeof(weather_data_t));
+        close(shm_fd);
+        return -1;
+    }
+
+    if (sem_wait(sem) == -1) {
+        perror("sem_wait");
+        ret = -1;
+        goto cleanup;
+    }
+
+    memcpy(data, shared_data, sizeof(weather_data_t));
+
+    sem_post(sem);
+
+cleanup:
+    sem_close(sem);
+    munmap(shared_data, sizeof(weather_data_t));
+    close(shm_fd);
+    return ret;
+}