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Rush - A Unix shell written in Rust

Rush is a POSIX sh-compatible shell implemented in Rust. It provides both interactive mode with a REPL prompt and script mode for executing commands from files. The shell supports basic shell features like command execution, pipes, redirections, environment variables, and built-in commands.

Pun-der the Hood

In a hurry? Don’t bash your head against it—Rush it.
When your pipelines need a drum solo, put them on Rush and let the commands Neil-Peart through.
Tom Sawyer tip: chores go faster when you make them look like a Rush job; no need to paint the fence by hand when the shell can whitewash it with a one-liner.
Alias your productivity: alias hurry='rush -c "do the thing"'—because sometimes you just need to rush to judgment.
This shell doesn’t just run fast; it gives you the Rush of a clean exit status.

Features

Command Execution: Execute external commands and built-in commands.
Pipes: Chain commands using the | operator.
Redirections: Input (<) and output (>, >>) redirections.
Command Substitution: Execute commands and substitute their output inline.
- $(command) syntax: echo "Current dir: $(pwd)"
- `command` syntax: echo "Files: ls | wc -l"
- Variable expansion within substitutions: echo $(echo $HOME)
- Error handling with fallback to literal syntax
Environment Variables: Full support for variable assignment, expansion, and export.
- Variable assignment: VAR=value and VAR="quoted value"
- Variable expansion: $VAR and special variables ($?, $$, $0)
- Export mechanism: export VAR and export VAR=value
- Variable scoping: Shell variables vs exported environment variables
Control Structures:
- if statements: if condition; then commands; elif condition; then commands; else commands; fi
- case statements with glob pattern matching: case word in pattern1|pattern2) commands ;; *.txt) commands ;; *) default ;; esac
Built-in Commands:
- cd: Change directory
- exit: Exit the shell
- echo: Print text
- pwd: Print working directory
- env: List environment variables
- export: Export variables to child processes
- unset: Remove variables
- source: Execute a script file with rush (bypasses shebang)
- pushd: Push directory onto stack and change to it
- popd: Pop directory from stack and change to it
- dirs: Display directory stack
- alias: Define or display aliases
- unalias: Remove alias definitions
- test / [: POSIX-compatible test builtin with string and file tests
- help: Show available commands
Tab Completion: Intelligent completion for commands, files, and directories.
- Command Completion: Built-in commands and executables from PATH
- File/Directory Completion: Files and directories with relative paths
- Directory Traversal: Support for nested paths (src/, ../, /usr/bin/)
- Home Directory Expansion: Completion for ~/ and ~/Documents/ paths
Signal Handling: Graceful handling of SIGINT (Ctrl+C) and SIGTERM.
Line Editing and History: Enhanced interactive experience with rustyline.

Latest Updates

Environment Variable Support

Rush now provides comprehensive environment variable support with full POSIX compliance:

Variable Assignment: Support for both simple and quoted assignments
```
MY_VAR=hello
MY_VAR="hello world"
NAME="Alice"
```
Variable Expansion: Expand variables in commands with $VAR syntax
```
echo "Hello $NAME"
echo "Current directory: $PWD"
```

Special Variables: Built-in support for special shell variables

echo "Last exit code: $?"
echo "Shell PID: $$"
echo "Script name: $0"

Export Mechanism: Export variables to child processes
```
export MY_VAR
export NEW_VAR=value
```
Variable Management: Full lifecycle management with unset
```
unset MY_VAR
```
Multi-Mode Support: Variables work consistently across all execution modes
- Interactive mode: Variables persist across commands
- Script mode: Variables available throughout script execution
- Command string mode: Variables work in -c command strings

Example usage:

# Set and use variables
MY_VAR="Hello from Rush"
echo "Message: $MY_VAR"

# Export to child processes
export MY_VAR
env | grep MY_VAR

# Use in pipelines
echo "$MY_VAR" | grep "Rush"

# Special variables
if true; then echo "Success ($?)"; fi

Case Statements with Glob Pattern Matching

Rush now supports advanced case statements with full glob pattern matching capabilities:

Glob Patterns: Use wildcards like * (any characters), ? (single character), and [abc] (character classes)
Multiple Patterns: Combine patterns with | (e.g., *.txt|*.md)
POSIX Compliance: Full support for standard case statement syntax
Performance: Efficient pattern matching using the glob crate

Example usage:

case $filename in
    *.txt|*.md) echo "Text file" ;;
    *.jpg|*.png) echo "Image file" ;;
    file?) echo "Single character file" ;;
    [abc]*) echo "Starts with a, b, or c" ;;
    *) echo "Other file type" ;;
esac

Directory Stack Support (pushd/popd/dirs)

Rush now supports directory stack management with the classic Unix pushd, popd, and dirs commands:

pushd <directory>: Changes to the specified directory and pushes the current directory onto the stack
popd: Pops the top directory from the stack and changes to it
dirs: Displays the current directory stack

Example usage:

# Start in home directory
pwd
# /home/user

# Push to /tmp and see stack
pushd /tmp
# /tmp /home/user

# Push to another directory
pushd /var
# /var /tmp /home/user

# See current stack
dirs
# /var /tmp /home/user

# Pop back to /tmp
popd
# /tmp /home/user

# Pop back to home
popd
# /home/user

This feature is particularly useful for:

Quickly switching between multiple working directories
Maintaining context when working on different parts of a project
Scripting scenarios that require directory navigation

Command Substitution

Rush now supports comprehensive command substitution with both $(...) and `...` syntax:

Dual Syntax Support: Both $(command) and `command` work identically
Immediate Execution: Commands are executed during lexing and output is substituted inline
Variable Expansion: Variables within substituted commands are properly expanded
Error Handling: Failed commands fall back to literal syntax preservation
Environment Integration: Child processes inherit shell environment variables
Multi-line Support: Handles commands with multiple lines and special characters

Example usage:

Condensed Current Working Directory in Prompt

Rush now displays a condensed version of the current working directory in the interactive prompt:

Condensed Path: Each directory except the last is abbreviated to its first letter (preserving case)
Full Last Directory: The final directory in the path is shown in full
Dynamic Updates: The prompt updates automatically when changing directories

Example prompt displays:

/h/d/p/r/rush $
/u/b/s/project $
/h/u/Documents $

This feature provides context about your current location while keeping the prompt concise.

# Basic command substitution
echo "Current directory: $(pwd)"
echo "Files in directory: `ls | wc -l`"

# Variable assignments with substitutions
PROJECT_DIR="$(pwd)/src"
FILE_COUNT="$(ls *.rs 2>/dev/null | wc -l)"

# Complex expressions
echo "Rust version: $(rustc --version | cut -d' ' -f2)"
echo "Files modified today: $(find . -name '*.rs' -mtime -1 | wc -l)"

# Error handling
NONEXISTENT="$(nonexistent_command 2>/dev/null || echo 'command failed')"
echo "Result: $NONEXISTENT"

# Multiple commands
echo "Combined output: $(echo 'Hello'; echo 'World')"

Command substitution works seamlessly with:

Pipes and Redirections: $(echo hello | grep ll) > output.txt
Variable Expansion: echo $(echo $HOME)
Quoted Strings: echo "Path: $(pwd)"
Complex Commands: $(find . -name "*.rs" -exec wc -l {} \;)

Built-in Alias Support

Rush now provides comprehensive built-in alias support, allowing you to create shortcuts for frequently used commands:

Create Aliases: Define shortcuts with alias name=value syntax
List Aliases: View all defined aliases with alias command
Show Specific Alias: Display a single alias with alias name
Remove Aliases: Delete aliases with unalias name
Automatic Expansion: Aliases are expanded automatically during command execution
Recursion Prevention: Built-in protection against infinite alias loops

Example usage:

# Create aliases
alias ll='ls -l'
alias la='ls -la'
alias ..='cd ..'
alias grep='grep --color=auto'

# List all aliases
alias
# Output:
# alias ll='ls -l'
# alias la='ls -la'
# alias ..='cd ..'
# alias grep='grep --color=auto'

# Show specific alias
alias ll
# Output: alias ll='ls -l'

# Use aliases (they expand automatically)
ll
la /tmp
..

# Remove aliases
unalias ll
alias  # ll is no longer listed

# Error handling
unalias nonexistent  # Shows: unalias: nonexistent: not found

Key Features:

POSIX Compliance: Follows standard alias syntax and behavior
Session Persistence: Aliases persist throughout the shell session
Complex Commands: Support for multi-word commands and pipelines
Variable Expansion: Variables in aliases are expanded when defined
Safety: Automatic detection and prevention of recursive aliases

Advanced Usage:

# Complex aliases with pipes and redirections
alias backup='cp -r ~/Documents ~/Documents.backup && echo "Backup completed"'
alias count='find . -name "*.rs" | wc -l'

# Aliases with variables (expanded at definition time)
MY_DIR="/tmp"
alias cleanup="rm -rf $MY_DIR/*"

# Function-like aliases
alias mkcd='mkdir -p "$1" && cd "$1"'  # Note: $1 won't work as expected

Implementation Details:

Aliases are expanded after lexing but before parsing
Only the first word of a command can be an alias
Expansion is recursive (aliases can reference other aliases)
Built-in protection against infinite recursion
Aliases work in all execution modes (interactive, script, command)

Test Builtin with Conditional Logic

Rush now provides comprehensive support for the POSIX test builtin command and its [ bracket syntax, enabling powerful conditional logic in shell scripts:

String Tests: Check if strings are empty (-z) or non-empty (-n)
File Tests: Test file existence (-e), regular files (-f), and directories (-d)
Dual Syntax Support: Both test and [ syntax work identically
POSIX Compliance: Full compatibility with standard test command behavior
Error Handling: Proper exit codes (0=true, 1=false, 2=error)
Integration: Seamless integration with shell control structures

Example usage:

# String tests
if test -z ""; then echo "Empty string"; fi
if [ -n "hello" ]; then echo "Non-empty string"; fi

# File tests
if test -e "/tmp/file.txt"; then echo "File exists"; fi
if [ -d "/tmp" ]; then echo "Is directory"; fi
if test -f "/etc/passwd"; then echo "Is regular file"; fi

# Complex conditions
if [ -n "$MY_VAR" ] && test -e "$CONFIG_FILE"; then
    echo "Variable set and config file exists"
fi

# Error handling
test -x "invalid_option"  # Returns exit code 2
exit_code=$?
if [ $exit_code -eq 2 ]; then echo "Invalid option used"; fi

Key Features:

String Operations: -z (zero length) and -n (non-zero length) tests
File Operations: -e (exists), -f (regular file), -d (directory)
Bracket Syntax: [ condition ] works identically to test condition
Exit Codes: 0 (true), 1 (false), 2 (error/invalid usage)
Variable Expansion: Variables are properly expanded in test conditions
Nested Conditions: Works with complex if/elif/else structures

Advanced Usage:

# Variable existence checks
MY_VAR="hello world"
if test -n "$MY_VAR"; then
    echo "MY_VAR is set to: $MY_VAR"
fi

# Safe file operations
TARGET_FILE="/tmp/safe_file.txt"
if test -e "$TARGET_FILE"; then
    echo "File exists, backing up..."
    mv "$TARGET_FILE" "$TARGET_FILE.backup"
fi

# Directory creation with checks
TARGET_DIR="/tmp/test_dir"
if test -d "$TARGET_DIR"; then
    echo "Directory already exists"
else
    mkdir -p "$TARGET_DIR"
    echo "Directory created"
fi

The test builtin is fully integrated with Rush's control structures, enabling complex conditional logic in scripts while maintaining POSIX compatibility.

Installation

Prerequisites

Rust (edition 2021 or later)

Build

Clone the repository:

git clone https://github.com/drewwalton19216801/rush.git
cd rush

Build the project:
```
cargo build --release
```

The binary will be available at target/release/rush.

Usage

Interactive Mode

Run the shell without arguments to enter interactive mode:

./target/release/rush

You'll see a prompt showing the condensed current working directory followed by $ (e.g., /h/d/p/r/rush $ ) where you can type commands. Type exit to quit.

Script Mode

Execute commands from a file:

./target/release/rush script.sh

The shell will read and execute each line from the script file. Note that when using script mode, shebang lines (e.g., #!/usr/bin/env bash) are not bypassed - they are executed as regular comments.

Command Mode

Execute a command string directly:

./target/release/rush -c "echo Hello World"

The shell will execute the provided command string and exit.

Source Command

The source built-in command provides a way to execute script files while bypassing shebang lines that may specify other shells:

source script.sh

This is particularly useful for:

Executing scripts written for rush that contain #!/usr/bin/env rush shebangs
Running scripts with shebangs for other shells (like #!/usr/bin/env bash) using rush instead
Ensuring consistent execution environment regardless of shebang declarations

Unlike script mode (running ./target/release/rush script.sh), the source command automatically skips shebang lines and executes all commands using the rush interpreter.

Examples

Run a command: ls -la
Use pipes: ls | grep txt
Redirect output: echo "Hello" > hello.txt
Change directory: cd /tmp
Print working directory: pwd
Directory stack management:
- Push directory: pushd /tmp
- Pop directory: popd
- Show stack: dirs
Execute a script: source script.sh
Execute a script with shebang bypass: source examples/basic_commands.sh
Execute elif example script: source examples/elif_example.sh
Execute case example script: source examples/case_example.sh
Execute variables example script: source examples/variables_example.sh
Execute complex example script with command substitution: source examples/complex_example.sh
Alias management:
- Create aliases: alias ll='ls -l'; alias la='ls -la'
- List aliases: alias
- Show specific alias: alias ll
- Remove aliases: unalias ll
- Use aliases: ll /tmp
Environment variables:
- Set variables: MY_VAR=hello; echo $MY_VAR
- Export variables: export MY_VAR=value; env | grep MY_VAR
- Special variables: echo "Exit code: $?"; echo "PID: $$"
- Quoted values: NAME="John Doe"; echo "Hello $NAME"
Use control structures:
- If statement: if true; then echo yes; else echo no; fi
- If-elif-else statement: if false; then echo no; elif true; then echo yes; else echo maybe; fi
- Case statement with glob patterns:
  - Simple match: case hello in hello) echo match ;; *) echo no match ;; esac
  - Glob patterns: case file.txt in *.txt) echo "Text file" ;; *.jpg) echo "Image" ;; *) echo "Other" ;; esac
  - Multiple patterns: case file in *.txt|*.md) echo "Document" ;; *.exe|*.bin) echo "Executable" ;; *) echo "Other" ;; esac
  - Character classes: case letter in [abc]) echo "A, B, or C" ;; *) echo "Other letter" ;; esac
Test builtin for conditional logic:
- String tests: if test -z "$VAR"; then echo "Variable is empty"; fi
- File tests: if [ -f "/etc/passwd" ]; then echo "File exists"; fi
- Combined conditions: if test -n "$NAME" && [ -d "/tmp" ]; then echo "Ready"; fi
- Error handling: test -x "invalid"; echo "Exit code: $?"
Command substitution:
- Basic substitution: echo "Current dir: $(pwd)"
- Backtick syntax: echo "Files: ls | wc -l"
- Variable assignments: PROJECT_DIR="$(pwd)/src"
- Complex commands: echo "Rust version: $(rustc --version | cut -d' ' -f2)"
- Error handling: RESULT="$(nonexistent_command 2>/dev/null || echo 'failed')"
- With pipes: $(echo hello | grep ll) > output.txt
- Multiple commands: echo "Output: $(echo 'First'; echo 'Second')"
Tab completion:
- Complete commands: cd → cd , e → echo , env , exit
- Complete files: cat f → cat file.txt
- Complete directories: cd src/ → cd src/main/
- Complete from PATH: l → ls , g → grep
- Complete nested paths: ls src/m → ls src/main/

Architecture

Rush consists of the following components:

Lexer: Tokenizes input into commands, operators, and variables with support for variable expansion, command substitution ($(...) and `...` syntax), and alias expansion.
Parser: Builds an Abstract Syntax Tree (AST) from tokens, including support for complex control structures, case statements with glob patterns, and variable assignments.
Executor: Executes the AST, handling pipes, redirections, built-ins, glob pattern matching, environment variable inheritance, and command substitution execution.
Shell State: Comprehensive state management for environment variables, exported variables, special variables ($?, $$, $0), current directory, directory stack, and command aliases.
Built-in Commands: Optimized detection and execution of built-in commands including variable management (export, unset, env) and alias management (alias, unalias).
Completion: Provides intelligent tab-completion for commands, files, and directories.

Dependencies

rustyline: For interactive line editing and history.
signal-hook: For robust signal handling.
nix: For Unix system interactions.
libc: For low-level C library bindings.
glob: For pattern matching in case statements.

Testing

Rush includes a comprehensive test suite to ensure reliability and correctness. The tests cover unit testing for individual components, integration testing for end-to-end functionality, and error handling scenarios.

Test Structure

Lexer Tests Tokenization of commands, arguments, operators, quotes, variable expansion, command substitution, and edge cases.
Parser Tests AST construction for single commands, pipelines, redirections, if-elif-else statements, case statements with glob patterns, and error cases.
Executor Tests Built-in commands, external command execution, pipelines, redirections, case statement execution with glob matching, command substitution execution, and error handling.
Completion Tests Tab-completion for commands, files, directories, path traversal, and edge cases.
Integration Tests End-to-end command execution, including pipelines, redirections, variable expansion, case statements, and command substitution.
Main Tests Error handling for invalid directory changes.

Running Tests

Run all tests with:

cargo test

Run specific test modules:

cargo test lexer
cargo test parser
cargo test executor
cargo test integration

Test Coverage

The test suite provides extensive coverage of:

Command parsing and execution
Built-in command functionality (cd, echo, pwd, env, exit, help, source, export, unset, pushd, popd, dirs, alias, unalias, test, [)
Pipeline and redirection handling
Control structures (if-elif-else statements, case statements with glob patterns)
Command substitution ($(...) and `...` syntax, error handling, variable expansion)
Environment variable support (assignment, expansion, export, special variables)
Variable scoping and inheritance
Tab-completion for commands, files, and directories
Path traversal and directory completion
Error conditions and edge cases
Signal handling integration

Contributing

Contributions are welcome! Please fork the repository, make your changes, and submit a pull request.

License

This project is licensed under the MIT License. See LICENSE.txt for details.

Project URL

https://github.com/drewwalton19216801/rush-sh

rush-sh 0.2.1

Rush - A Unix shell written in Rust

Pun-der the Hood

Features

Latest Updates

Environment Variable Support

Case Statements with Glob Pattern Matching

Directory Stack Support (pushd/popd/dirs)

Command Substitution

Condensed Current Working Directory in Prompt

Built-in Alias Support

Test Builtin with Conditional Logic

Installation

Prerequisites

Build

Usage

Interactive Mode

Script Mode

Command Mode

Source Command

Examples

Architecture

Dependencies

Testing

Test Structure

Running Tests

Test Coverage

Contributing

License

Project URL