04 Shell

Overview

This sample demonstrates the use of Zephyr’s shell subsystem, providing a command-line interface for interacting with the system.

This sample is useful for:

Understanding the shell subsystem
Learning about command history, completion, and help
Hardware validation, testing, and debugging
Exploring kernel and device information at runtime

Key Features:

Interactive command-line interface
Tab completion and command history
Built-in commands for kernel, device, and sensor information
Support for I2C scanning and sensor reading
Custom command registration examples

Building

This sample uses qemu_x86 because the shell subsystem requires a UART backend for interactive use, which QEMU provides.

This application can be built and executed on QEMU x86 as follows:

host:~$ west build -b qemu_x86 samples/04_shell -p
host:~$ west build -t run

To exit QEMU, press CTRL+a, x.

To build for a real board (e.g., reel_board@2), use:

host:~$ west build -b reel_board@2 samples/04_shell -p
host:~$ west flash

Sample Output

After connecting to the shell, you can use various commands:

uart:~$
  bypass              clear               date
  demo                device              devmem
  dynamic             help                history
  kernel              log                 log_test
  rem                 resize              retval
  section_cmd         shell               shell_uart_release
  stats               version

List kernel threads:

uart:~$ kernel thread list
Threads:
*0x1243a0 shell_uart
     options: 0x0, priority: 14 timeout: 0
     state: queued, entry: 0x109399
     Total execution cycles: 20502688 (0 %)
     stack size 2048, unused 872, usage 1176 / 2048 (57 %)

 0x12dea0 sysworkq
     options: 0x1, priority: -1 timeout: 0
     state: pending, entry: 0x11204a
     Total execution cycles: 624459 (0 %)
     stack size 1024, unused 648, usage 376 / 1024 (36 %)

Exit QEMU by pressing CTRL+a, x.