DiSH is a simple command interpreter

Tasks

• Lexer
  • Recognize tokens
    • UnitTests
  • Quotes mode
• Parser
  • Simple command
    • UnitTests
  • Pipeline
    • UnitTests
• Executor
  • Simple command
    • Python tests
  • Pipeline
    • Python tests

Lexer

Token table

Token	Lexeme
BACKGROUND	&
SEQUENCE	;
INPUT_REDIRECTION	<
OUTPUT_REDIRECTION	>
APPEND_REDIRECTION	>>
PIPE	|
LBRACKET	(
RBRACKET	)
AND	&&
OR	||
WORD	everything else

Parser

Priority table

Priority	Operator
0	()
1	|
2	< > >>
3	&& ||
4	; &

Grammar

COMMAND_LINE -> SEQUENCE
          | SEQUENCE ;
          | SEQUENCE &
SEQUENCE -> SEQUENCE ; ANDOR
          | SEQUENCE & ANDOR
          | ANDOR
ANDOR -> ANDOR && COMMAND
       | ANDOR || COMMAND
       | COMMAND
COMMAND -> PIPELINE INPUT OUTPUT
INPUT -> < word
       | e
OUTPUT -> > word
        | >> word
        | e
PIPELINE -> PIPELINE | SIMPLE_COMMAND
          | SIMPLE_COMMAND
SIMPLE_COMMAND -> (SEQUENCE)
                | word ARGS
ARGS -> ARGS word
      | e

BNF

START ::= PIPELINE "\n"
PIPELINE ::= SIMPLE_COMMAND ("|" SIMPLE_COMMAND)*
SIMPLE_COMMAND ::= word (word)*