nsh

The Neikos Shell

This shell is for my personal use primarily. It is intended to run on my system, a linux environment. I do not promise any compatibility to other platforms.

Goals

Be fast and correct.

That's it really, it should be usable too.

Syntax

The syntax is kept small and meant to be out of the way.

These constructs exist:

• for:

    $ for var in $(seq 1 5) do
        echo $var;
      end

• { }:

    $ [ $var = 1 ] && { 
        echo '$var is 1';
        echo "And the path is: $PATH"
    }

• && and || for chaining
• |, > and < for piping
• # are line comments

Variables

• Each shell has its own set of variables, they are accessed through the % prefix.
• > $var in command position will resolve the variable and call it's value
• > $var = <value> will set the value to the variable.
• Variables are arrays, seperated by spaces
• > $var = a b c d e f g will be an array of 7 elements
• > $var = "a b c" e f g will be an array of 4 elements
• > echo $var will return the whole array
• > echo $var[0] will return the first element
• > echo $var[-1] will return the last element
• > echo $var[10] will not run and error instead
• > echo $var[10]? will return the 11th entry or empty string

Environment Variables

• EnvVars are accessed through the % prefix.
• > %var resolves and substitutes the value and executes it
• > %var = <value> sets the value to the variable
• > echo %var substitutes the EnvVar
• If the EnvVar does not exist, an empty string is substituted

Substitution

• Substitution is done after expressions are formed
• This means that substituting a command with spaces will not be split up
• > command $variable #FOO, here command will be called with two arguments which might have spaces themselves

Quotes

• Both type of quotes work similarly, however, double quotes also substitute (and evaluate) any variables or subshells
• Single quotes do not do substitution

Aliases

Aliases are done through executable files that are earlier in the path with the same name

Functions

No builtin functions, the idea is to be nimble, executables are pretty nimble

Autocomplete

Basic autocomplete will exist for commands and from the current path

History

The history will be saved, unless started with the option to disable it

Suggestions

History and path should be able to work together and suggest possible paths to be executed