v0.1.0 — Phase 1: Core Shell

Full POSIX-compliant shell implementation with lexer, parser, expander, executor, and builtin commands.

Features

Core Shell Components

• Lexer — Complete POSIX tokenization with quote preservation, 24 unit tests
• Parser — Recursive descent AST supporting all POSIX constructs (if/for/while/case/function/subshell)
• Expander — Variable expansion ($VAR, ${VAR}), command substitution, arithmetic expansion
• Executor — Fork/exec pipeline, redirects, job control with signal handling

Control Flow & Variables

• ✅ Variable Expansion — $VAR and ${VAR} syntax working in all contexts
• ✅ For-Loop Variable Binding — Loop variables properly scoped and accessible
• ✅ Case-Statement Pattern Matching — POSIX glob patterns (*, ?, [...]) fully functional
• ✅ Loop Control — break and continue builtins fully implemented
• ✅ Process Replacement — exec builtin with libc::execvp integration

Builtin Commands

• echo, printf, exit, return
• cd, pwd, export, unset, env
• source/., set, shift
• test/[, read, trap
• break, continue, exec
• jobs, fg, bg
• alias, unalias, true, false

Execution Modes

• ✅ Command Mode (-c flag) — Execute inline commands
• ✅ File Mode (-f flag) — Execute script files
• ✅ Stdin Mode — Read and execute piped scripts
• ✅ Interactive Mode — REPL with history and prompt

Process Management

• Fork/exec pipeline with proper exit status propagation
• Background execution (&) with process groups
• Subshell execution with process isolation
• Signal handling (SIGCHLD, SIGINT, SIGQUIT)
• Job control with fg/bg/jobs commands

Quality Metrics

Known Limitations

• Multiline compound commands require semicolons (parser limitation, fix planned for v0.1.0-beta)
• 4 POSIX tests ignored with documented reasons (see POSIX.md)

Getting Started

```bash

Run a command

modsh -c 'echo "Hello, World!"'

Execute a script file

modsh -f script.sh

Interactive shell

modsh

Pipe a script

echo 'for x in 1 2 3; do echo $x; done' | modsh
```

Testing

```bash
cargo test # Run all tests
cargo clippy -- -D warnings # Lint check
cargo fmt --check # Format check
cargo audit # Security scan
```

Documentation

• CHANGELOG.md — Full release notes
• README.md — Quick start guide
• ARCHITECTURE.md — Design details
• Plans.md — Phase 2+ roadmap
• TODO.md — Task tracking

Release Date: 2026-05-21 | Status: ✅ Alpha Ready | License: Apache 2.0 / BSL 1.1