# Chapter 5: An Interactive Shell

## Sample code

- Directory: `docs/os-on-arduino/code/05_shell`

```bash
uv run pio run -d 05_shell -t upload
uv run pio device monitor -b 115200
```

## Source code

The sketch for this chapter. Click a file name to expand. The code is mirrored automatically from the manuscript repository, so what you see here is always current.

:::{dropdown} `src/main.cpp` — 96 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/05_shell/src/main.cpp)

```{literalinclude} ../../../../code/05_shell/src/main.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `include/os_kernel.h` — 79 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/05_shell/include/os_kernel.h)

```{literalinclude} ../../../../code/05_shell/include/os_kernel.h
:language: cpp
:linenos:
```

:::

:::{dropdown} `include/shell.h` — 23 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/05_shell/include/shell.h)

```{literalinclude} ../../../../code/05_shell/include/shell.h
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/os_kernel.cpp` — 281 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/05_shell/src/os_kernel.cpp)

```{literalinclude} ../../../../code/05_shell/src/os_kernel.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/shell.cpp` — 186 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/05_shell/src/shell.cpp)

```{literalinclude} ../../../../code/05_shell/src/shell.cpp
:language: cpp
:linenos:
```

:::


## On the board

```{raw} html
<figure style="margin:1.5rem auto; max-width:70%;">
  <video src="../_static/ch05_kill.mp4" autoplay loop muted playsinline preload="metadata"
         style="width:100%; border-radius:8px;" aria-label="第5章を実機で動かし、kill 1 と exec 1 を打った動画"></video>
  <figcaption style="font-size:0.9em;"><code>kill 1</code> stops task LED1 and the L LED stops blinking (it stays as it was); <code>exec 1</code> brings it back. The left half of the matrix (LED2) keeps blinking every 0.5 s throughout. (Filmed with a webcam at 30 fps.)</figcaption>
</figure>
```

## In the simulator

Without the board, the same firmware running in the {doc}`simulator <../getting-started/simulator>` looks like this.

```{figure} ../_static/sim_ch05_kill.gif
:name: fig-ch05-sim
:width: 80%

With L (LED1) and the left half of the matrix (LED2) blinking, `kill 1` from the shell stops only L, and `exec 1` starts it again. The left half never stops. (Recorded in the simulator.)
```

## Pitfalls

(Collected from reader questions — ask via
[GitHub Issues](https://github.com/iory/build-your-own-arduino-rtos/issues).)