How it works

This section describes how library works from the basic perspective.

LwSHELL is designed to accept computer-command-like input, in format of cmdname param1 "param 2 with space", parse it properly and search for function callback that is assigned for specific cmdname.

Library starts processing input line on line-feed or carriage-return characters. It splits tokens by space character:

  • Tokens must not include space character or it will be considered as multi-token input

  • To use space character as token input, encapsulate character in double-quotes

Command structure

Every command has assigned dedicated name and must start with it. Application must take care to input exact command name since commands are case-sensitive, mycmd is a different command than Mycmd.

Command structure looks like:

  • It must start with command name and has at least one (1) parameter, eg. mycommand. Command name is counted as first parameter

  • It may have additional parameters split with space character

  • Every input is parsed as string, even if parameter is string


To use space as an input, encapsulate it with double quotes, eg. mycmd param1 "param 1 has spaces"

Register command

Application must register command(s) to be used by the system. This can be done using lwshell_register_cmd() function which accepts command name, command function and optional command description

Command description

Every command can have assigned its very simple description text, know as help text. Description is later accessible with special command input that has 2 parameters in total and second is -h, cmdname -h.

Data output

To properly work with the library, application must input data to process by using lwshell_input() function. Thanks to the library implementation, it is possible to get data feedback and be able to implement OS-like console.

To enable data-output feature, define your output callback function and assign it with lwshell_set_output_fn() function.

Data outputs works on:

  • Special characters for carriage return and line-feed

  • Special character backspace that returns set of characters to implement backspace-like event on your output

  • Actual input character printed back for user feedback

  • cmdname -h feature works to print simple help text