Crate oursh[−][src]

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Documentation CI Dependencies

This shell should be both POSIX compatible and yet modern and exciting. Fancy features should not be prevented by POSIX compatibility. This will effect the design of the shell.

The name of the shell is oursh which is both somewhat unique, and memorable. It’s also a nice name to play with pseudo-satirical themes… right comrade? It’s short (ish) and sneakily fits rs in it, which is the extension of Rust programs, the language this will be written in.

Features

  • POSIX compatibility
    • Simple commands ls
    • Quotes echo "foo"; echo 'bar'
    • Assignment LOG=trace cargo run
    • Variables echo $foo
    • Special variables echo $?; echo $1
    • Boolean status syntax ! true && false || true
    • Conditionals if ; then ; elif ; then ; else ; fi
    • Compound commands { ls; date; }
    • Subshells (sleep 1; date)
    • Background jobs { sleep 1; date; }& date
    • Redirection date > now.txt
    • Pipes ls | wc -l
  • Shebang block programs
    • Alternate syntax {# ...}
    • Hashlang syntax {#lang; ...}, i.e. {#posix ls}
    • Shebang syntax {#!/usr/bin/env ruby; puts :sym}
  • bash/zsh autocomplete compatibility
    • Command completion
    • Path completion
    • Variable completion
    • Job completion
    • Syntax completion
    • man / -h / --help parsing
  • Multi-line input
  • Modern scripting language
    • Macros
    • Types
    • Higher-order functions
    • Threading?
  • Obfuscated strings (!'password'!)
  • mosh like remote session support
  • Smart history, sync’d across devices
  • Pipe old commands without rerunning
  • Package manager
  • Sane defaults
  • Fast

POSIX Reference

See the following sections for building the POSIX sh compliant program language, and interactive terminal based REPL. While this mainly defines the posix module, there are a lot of common concepts to all shells here.

  • 3§2 Shell Command Language
    • 10.2 Shell Grammar Rules
  • 2§2.5 Standard I/O Streams
  • 3§1.6 Built-In Utilities
  • 3§1.4 Utility Description Defaults
  • 2§2.3 Error Numbers
  • 1§11 General Terminal Interface
  • 2§2.4 Signal Concepts

Implementation

This shell will be written in Rust with minimal dependencies. Notably termios and libc will likely be used. The parsing library will be lalrpop, which should support the syntax we want somewhat easily, though grammar’s in general can be a tricky beast.

We will want to create a few internal modules for the shell.

This design is subject to change.

  • process - sub-process execution management.
  • program - parser and interpreter for the syntax of the shell.
    • posix - POSIX (sh-like) syntax.
    • modern - Modified syntax for supporting “modern” features, like lambdas.
  • repl - syntax aware, read eval print loop for an underlying terminal.
    • history - records previous execution to a shared DB.
    • completion - searches for autocompletions based on partial syntax.
      • bash - bash completion support.
      • zsh - zsh completion support.
      • parse - dynamic completion generation, from man for example.
    • sync - remote session and DB synchronization.
  • invocation - loading for .ourshrc and others.
  • package - simplistic package manager support (builtin function).

Modules

invocation

WTF!

process

Subprocess execution management.

program

Parsing and handling program syntax(es) of the shell.

Macros

debug

Print debug information to stderr.