small_tel

The weather_proxy package offers a lightweight daemon (weather_proxy) that receives data from supermeteodaemon via a TCP or UNIX socket, parses it, and makes it available locally through a shared memory segment. A client library (libweather.so) and a simple command-line utility (chkweather) are also provided to easily retrieve and check weather conditions.

Overview

The main daemon (weather_proxy) connects to a running supermeteodaemon process, parses the incoming FITS-header-style data stream, and regularly updates a POSIX shared memory segment (/weather_shm). A named semaphore (/weather_sem) protects the shared data. The client library offers the get_weather_data() function to read this shared memory and return the data in a weather_data_t structure. The chkweather utility uses this function to quickly check the current weather status and produce an exit code suitable for scripting.

Components

The project consists of the following source files:

File	Description
`weather_daemon.c`	The main proxy daemon.
`weather_client.c`	The client library (`libweather.so`) with `get_weather_data()`.
`weather_data.h`	Common data structure and definitions.
`chkweather.c`	A simple command‑line tool to check weather status.
`weather_clt_example.c`	Example usage of the client library.
`Makefile`	Builds the daemon, client library, and utilities.

Building

The package requires a C compiler (e.g., gcc) and the usefull_macros library. To install the latter clone its code and use cmake/make:

git clone --depth=1 https://github.com/eddyem/snippets_library
cd snippets_library
mkdir build
cd build
cmake ..
make
su -c "make install"
# or "sudo make install" if you have "sudo" configured

Then build the project:

make

This produces:

weather_proxy – the main daemon
libweather.so – the shared client library
chkweather – the weather check utility
weather_clt_example – an example client

To install:

su -c "make install"

This copies libweather.so to /usr/local/lib, installs weather_data.h in /usr/local/include, and places the executables in /usr/local/bin.

Usage

Running the proxy daemon (`weather_proxy`)

weather_proxy -n <node> [-u] [-l <logfile>] [-p <pidfile>] [-f <fitsheader>] [-v]

Options

Option	Description
`-n <node>`	Connection endpoint. For TCP: `host:port`. For UNIX sockets: path to socket. Required.
`-u`	Use a UNIX socket instead of TCP.
`-l <file>`	Write log messages to the specified file.
`-p <file>`	PID file (default `/tmp/weather_proxy.pid`).
`-f <file>`	Save the latest weather data as a FITS‑header file.
`-v`	Increase verbosity (can be used multiple times).

Example

Connect to supermeteodaemon on TCP port 12345 at localhost:

weather_proxy -n localhost:12345 -v -l /var/log/weather_proxy.log

Use a UNIX socket and store the FITS header:

weather_proxy -n /tmp/superweather.sock -u -f /tmp/latest_weather.header

Checking weather (`chkweather`)

chkweather reads the shared memory and prints the current weather data. It returns an exit code according to the weather condition:

Exit Code	Meaning
`0`	Weather is good – observations may start.
`1`	Weather is bad – cannot start, but ongoing observations may continue.
`2`	Weather is terrible – close the dome, park.
`3`	Weather is prohibited – power off equipment, prepare to shut down the computer (or data is too old).

Example:

if ./chkweather; then
    echo "Conditions are good - starting observations"
else
    echo "Bad weather - stopping"
fi

Using the client library in your own code

The library provides a single function:

#include "weather_data.h"

int get_weather_data(weather_data_t *data);

It fills the weather_data_t structure with the latest weather information. Returns 0 on success, -1 on failure.

`weather_data_t` structure

typedef struct {
    weather_condition_t weather;    // condition (0..3)
    float windmax;                  // max wind in last hour (m/s)
    float wind;                     // current wind speed (m/s)
    float clouds;                   // sky "quality" (>2500 = good)
    float exttemp;                  // external temperature (°C)
    float pressure;                 // atmospheric pressure (mmHg)
    float humidity;                 // relative humidity (%)
    int rain;                       // 1 if rain is detected
    int forceoff;                   // forced power‑off flag
    time_t last_update;             // timestamp of the data
} weather_data_t;

The weather_condition_t enum:

Value	Meaning
`WEATHER_GOOD` (0)	Clear for observations
`WEATHER_BAD` (1)	Unfavourable but not critical
`WEATHER_TERRIBLE` (2)	Dangerous conditions – close and park
`WEATHER_PROHIBITED` (3)	Emergency – close, park and prepare for powering off

Example client:

#include "weather_data.h"
#include <stdio.h>

int main() {
    weather_data_t wd;
    if (get_weather_data(&wd) == 0) {
        printf("Weather: %d, Temp: %.1f C\n", wd.weather, wd.exttemp);
    }
    return 0;
}

Compile with:

gcc -o myclient myclient.c -lweather

Data Flow

supermeteodaemon collects data from various sensors and outputs it as lines of KEY=VALUE pairs (FITS-header style).
weather_proxy connects to the socket, sends a "get\n" command, and parses the incoming lines.
It extracts the fields: WEATHER, WINDMAX1, PRECIP, CLOUDS, WIND, EXTTEMP, PRESSURE, HUMIDITY, FORCEOFF, and TMEAS (the timestamp).
The data is stored in a POSIX shared memory segment (/weather_shm) and is protected by a named semaphore (/weather_sem).
Client applications (like chkweather or your own code) use get_weather_data() to read the shared memory safely.

Signals

The daemon responds to:

SIGUSR1 – Forbid observations (sets an internal forbidden flag which overrides the current weather to WEATHER_PROHIBITED).
SIGUSR2 – Permit observations (clears the forbidden flag).

These signals are only handled by the worker child process; the parent monitor process ignores them. So you can send them simply by killall -sUSR1 weather_proxy.

FITS‑Header Output

If the -f <file> option is given, the daemon writes each received KEY=VALUE line to a temporary file and, when the data set is complete (i.e., the TWEATH line is received), it atomically replaces the target file. This produces a plain‑text file that can be used as a FITS header or for other applications.

Example generated file:

WIND    =                 4.30 / Wind, m/s
WINDMAX =                 5.90 / Maximal wind speed for last 24 hours
WINDMAX1=                 5.90 / Maximal wind speed for last hour
WINDDIR =                32.75 / Wind direction, degr (CW from north to FROM)
WINDDIR1=                25.97 / Mean wind speed direction for last hour
WINDDIR2=                35.37 / Mean wind speed^2 direction for last hour
HUMIDITY=                57.50 / Humidity, percent
EXTTEMP =                 9.00 / Ambient temperature, degC
PRESSURE=               585.72 / Atmospheric pressure, mmHg
PRECIP  =                    0 / Precipitation (1 - yes, 0 - no)
PRECIPLV=                 0.00 / Cumulative precipitation level (mm)
CLOUDS  =              2399.50 / Integral sky quality value (bigger - better)
WEATHER =                    0 / Weather (0..3: good/bad/terrible/prohibited)
TSINCERN=                   20 / Minutes since rain (20 means a lot of)
RAINPOW =                    0 / Rain strength, 0..255
RAINAVG =                    0 / Average rain strength, 0..255
RSAMBL  =                   48 / Ambient light by rain sensor, 0..255
RSFREEZ =                    0 / Rain sensor is freezed
TWEATH  =           1779085104 / Last weather time: 2026-05-18 09:18:24

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