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Interactive Line Editing

CJ's Shell uses the isocline line editor library to provide a powerful and feature-rich interactive editing experience. This document details all editing features currently available in cjsh.

Overview

Isocline is a modern, pure C line editing library that provides advanced terminal interaction capabilities. CJ's Shell leverages and extends isocline to offer:

  • Multiline editing with intelligent indentation
  • Real-time syntax highlighting
  • Context-aware tab completion
  • Inline hints and preview suggestions
  • Customizable key bindings
  • Line numbering for multiline input
  • Optional visible markers for whitespace characters
  • History search and management
  • Brace matching and auto-insertion
  • Spell correction
  • Fish-style abbreviations (automatic expansion on word boundaries)

All of these features can be configured through the cjshopt command or in your ~/.cjshrc configuration file.

Core Editing Features

Multiline Input

CJ's Shell supports seamless multiline input for complex commands, heredocs, and incomplete statements.

Features: - Automatic continuation when lines are incomplete - Smart indentation that aligns with the initial prompt - Line numbers for easy navigation - Both absolute and relative line numbering modes

Configuration: 

# Enable/disable multiline input (enabled by default)
cjshopt multiline on|off|status

# Enable/disable automatic indentation (enabled by default)
cjshopt multiline-indent on|off|status

# Configure how many prompt lines are shown before typing (default: 1)
cjshopt multiline-start-lines <count|status>

Multiline Detection: CJ's Shell automatically enters multiline mode when: - A line ends with a backslash (\) - Quotes are unclosed (", ', or backticks) - Control structures are incomplete (if, while, for, case, etc.) - Heredocs are being entered (<<, <<-) - Brackets/braces/parentheses are unclosed

Line Numbers

When in multiline mode, line numbers help track your position in the input.

Modes: - Absolute numbering: Shows actual line numbers (1, 2, 3, ...) - Relative numbering: Shows distance from current line (0 for current, ±N for others)

Configuration: 

# Enable absolute line numbers (default)
cjshopt line-numbers on
cjshopt line-numbers absolute

# Enable relative line numbers
cjshopt line-numbers relative

# Disable line numbers
cjshopt line-numbers off

# Check current status
cjshopt line-numbers status

Current Line Highlighting: The line containing the cursor can be highlighted differently: 

# Enable/disable current line number highlighting (enabled by default)
cjshopt current-line-number-highlight on|off|status

The line number styles can be customized: - ic-linenumbers: Style for regular line numbers - ic-linenumber-current: Style for the current line number

Visible Whitespace Markers

You can visualize whitespace characters while editing to spot stray spaces or indentation issues. When enabled, spaces are rendered using a subtle middle-dot marker.

Configuration: 

# Show or hide visible whitespace markers (disabled by default)
cjshopt visible-whitespace on|off|status

Pair this option with custom styling via cjshopt style_def ic-whitespace-char "<style>" to adjust the marker color.

Syntax Highlighting

Real-time syntax highlighting provides visual feedback as you type.

Highlighted Elements: - Commands (builtins, executables, aliases) - Keywords (if, then, else, while, for, etc.) - Strings (single and double quoted) - Variables and parameter expansions - Operators (pipes, redirections, logical operators) - Comments - Errors (unmatched quotes, invalid syntax)

Configuration: 

# Enable/disable syntax highlighting (enabled by default)
# Note: Can also be controlled with --no-syntax-highlighting flag

# Customize highlighting styles
cjshopt style_def <token_type> <style>

Available Style Names: - ic-keyword: Shell keywords - ic-command: Valid commands - ic-error: Invalid commands or syntax errors - ic-string: String literals - ic-comment: Comments - ic-operator: Operators - ic-variable: Variables - ic-number: Numeric literals - ic-bracket: Brackets and braces - ic-bracket-match: Matching bracket pairs

Syntax Highlighting Control: The syntax highlighter can be temporarily disabled with the --no-syntax-highlighting startup flag.

Completion System

CJ's Shell features a sophisticated completion system that provides context-aware suggestions.

Completion Types: - Command completion: Completes commands from PATH, builtins, aliases, and functions - File/directory completion: Completes paths with proper quoting and escaping - Variable completion: Completes shell variable names - User completion: Completes usernames (after ~) - Hostname completion: Completes hostnames (for ssh, scp, etc.)

Features: - Fuzzy matching for typo tolerance - Frequency-based ranking (commonly used completions appear first) - Source attribution (shows where completions come from) - Preview of selected completion - Automatic expansion with auto-tab

Configuration: 

# Enable/disable completion preview (enabled by default)
cjshopt completion-preview on|off|status

# Enable/disable auto-tab (disabled by default)
# Auto-tab automatically completes unique prefixes
cjshopt auto-tab on|off|status

# Configure case sensitivity (enabled by default)
cjshopt completion-case on|off|status

# Enable/disable spell correction (enabled by default)
cjshopt completion-spell on|off|status

Using Completions: - Press Tab to show completions - Press Tab again to cycle through options - Use arrow keys to navigate the completion menu - Press Enter to accept a completion - Press Esc to cancel

Hints and Inline Help

CJ's Shell provides inline hints and help to assist with command input.

Hints: When there's a single possible completion, a hint is displayed inline with dimmed text.

Features: - Shows the rest of the word being typed - Appears after a configurable delay - Can be accepted by pressing → (right arrow)

Configuration: 

# Enable/disable hints (enabled by default)
cjshopt hint on|off|status

# Set hint delay in milliseconds (0ms by default)
cjshopt hint-delay <milliseconds>

Inline Help: Short help messages are displayed for certain operations: - History search instructions - Completion menu navigation - Special key binding hints

Configuration: 

# Enable/disable inline help (enabled by default)
cjshopt inline-help on|off|status

Full Help: Press F1 at any time to display the complete key binding cheat sheet, regardless of the inline-help setting.

Fish-Style Abbreviations

CJ's Shell supports fish-style abbreviations that expand typed shortcuts into longer phrases as soon as you type a whitespace character or submit the line. This is powered directly by the isocline editor, so expansions happen inline without disrupting your cursor position or undo history.

Usage: - Define abbreviations with the abbr builtin: abbr gs='git status --short --branch' - Remove them with unabbr: unabbr gs - List all active abbreviations by running abbr with no arguments

Behavior: - Triggers expand when followed by a space, tab, newline, or when you press Enter - Expansion text is inserted in place of the trigger, preserving subsequent input - Abbreviations live in the current shell session and persist across reads within that session

Defaults: - abbr → abbreviate - unabbr → unabbreviate

Add abbr definitions to your ~/.cjshrc to load them automatically on startup.

Brace Matching and Auto-Insertion

Visual feedback for matching brackets, braces, and parentheses.

Brace Matching: When the cursor is next to a brace, its matching pair is highlighted. Unmatched braces are highlighted as errors.

Default Brace Pairs: - Parentheses: () - Square brackets: [] - Curly braces: {}

Auto-Insertion: When you type an opening brace, the closing brace is automatically inserted (enabled by default).

Default Auto-Insertion Pairs: - Parentheses: () - Square brackets: [] - Curly braces: {} - Double quotes: "" - Single quotes: ''

Note: Brace matching and auto-insertion are currently controlled by isocline's default settings and cannot be configured via cjshopt, but the feature is active.

History Management

History Features

CJ's Shell maintains a persistent command history with advanced search capabilities.

Features: - Persistent history across sessions - Configurable maximum entries - Duplicate suppression - History expansion (!, !!, !$, etc.) - Incremental search

Configuration: 

# Set maximum history entries
cjshopt set-history-max <number>

# Use default history size
cjshopt set-history-max default

# Check current setting
cjshopt set-history-max status

History File: History is stored at ~/.cache/cjsh/history.txt

Duplicate Handling: By default, duplicate entries are not stored in history to keep it clean and relevant.

Incremental Search (Ctrl+R): 1. Press Ctrl+R to enter search mode 2. Type to search through history 3. Press Ctrl+R again to find the next match 4. Press Enter to execute the found command 5. Press Esc to cancel search

History Navigation: - ↑ (Up Arrow): Previous command - ↓ (Down Arrow): Next command - Alt+<: Jump to oldest history entry - Alt+>: Jump to newest history entry

Key Bindings

CJ's Shell supports customizable key bindings with multiple profiles.

Key Binding Profiles

Available Profiles: - emacs: Emacs-style key bindings (default) - vi: Vi/Vim-style key bindings

Set Profile: 

cjshopt keybind profile set emacs|vi

Common Key Bindings (Emacs Mode)

Cursor Movement

  • Ctrl+A: Move to beginning of line
  • Ctrl+E: Move to end of line
  • Ctrl+F / →: Move forward one character
  • Ctrl+B / ←: Move backward one character
  • Alt+F: Move forward one word
  • Alt+B: Move backward one word
  • ↑: Previous line (or previous history)
  • ↓: Next line (or next history)

Editing

  • Ctrl+D: Delete character under cursor (or exit if line is empty)
  • Ctrl+H / Backspace: Delete character before cursor
  • Ctrl+W: Delete word before cursor
  • Alt+D: Delete word after cursor
  • Ctrl+U: Delete from cursor to beginning of line
  • Ctrl+K: Delete from cursor to end of line
  • Ctrl+Y: Paste (yank) last deleted text
  • Ctrl+T: Transpose characters
  • Alt+T: Transpose words

History

  • Ctrl+R: Incremental history search (reverse)
  • Ctrl+S: Incremental history search (forward)
  • ↑: Previous history entry
  • ↓: Next history entry
  • Alt+<: First history entry
  • Alt+>: Last history entry

Completion

  • Tab: Trigger completion / cycle through completions
  • Shift+Tab: Cycle backward through completions

Special

  • Ctrl+C: Cancel current input
  • Ctrl+D: Exit shell (when buffer is empty)
  • Ctrl+L: Clear screen
  • Enter: Execute command
  • F1: Show help / key binding cheat sheet
  • Esc: Cancel operation

Custom Key Bindings

You can inspect and customize key bindings through the cjshopt keybind subcommands:

# List all current key bindings (safe at runtime)
cjshopt keybind list

# Show available key binding profiles
cjshopt keybind profile list

# Activate a key binding profile (add to ~/.cjshrc to persist)
cjshopt keybind profile set vi

# Replace bindings for an action (config file only)
cjshopt keybind set cursor-left ctrl-h|left

# Add bindings without removing existing ones (config file only)
cjshopt keybind add delete-word-end alt-d

# Remove specific key bindings (config file only)
cjshopt keybind clear ctrl-h ctrl-b

# Remove all custom bindings for an action (config file only)
cjshopt keybind clear-action delete-word-end

# Restore default bindings (config file only)
cjshopt keybind reset

Key Specification Format: - ctrl-<key>: Control key combinations (e.g., ctrl-a) - alt-<key>: Alt/Meta key combinations (e.g., alt-f) - shift-<key>: Shift key combinations (e.g., shift-tab) - f<N>: Function keys (e.g., f1, f12) - <key>: Regular keys (e.g., tab, enter)

Command-Driven Key Bindings

Use the extended key binding namespace to trigger shell commands directly from key presses:

# List custom command key bindings (safe at runtime)
cjshopt keybind ext list

# Bind Ctrl+G to run a command (add to ~/.cjshrc)
cjshopt keybind ext set ctrl-g 'cjsh-widget accept'

# Remove a command binding
cjshopt keybind ext clear ctrl-g

# Clear every custom command binding
cjshopt keybind ext reset

Command key bindings typically leverage the cjsh-widget builtin to read or modify editor state. As with standard bindings, modifications must be placed in configuration files; inspection commands can run interactively, but setters only take effect during startup.

Prompt Customization

Prompt Cleanup

Control how the prompt is displayed after accepting input.

Features: - Removes full prompt and shows only trailing segment - Optional empty line insertion - Multiline truncation

Configuration: CJ's Shell automatically manages prompt cleanup based on your theme's settings. Theme authors can control: - cleanup_removes_prompt(): Whether to enable prompt cleanup - cleanup_adds_empty_line(): Whether to add an empty line after - cleanup_truncates_multiline(): Whether to truncate multiline input

Prompt Markers

The prompt system uses markers to indicate different states:

Primary Prompt Marker: Displayed at the end of the main prompt (default: "> ").

Continuation Prompt Marker: Displayed for continuation lines in multiline input.

Customization: These are typically set by your theme and control the visual appearance of prompts.

Terminal Features

Color Support

CJ's Shell automatically detects terminal capabilities:

Color Depth Detection: - Monochrome (1-bit) - 8 colors (3-bit) with bold for bright - 16 colors (4-bit) - 256 colors (8-bit) - True color (24-bit RGB)

Environment Variables: - COLORTERM: Indicates color capability (truecolor, 24bit, 256color, etc.)

Disable Colors: Use the --no-colors flag or set TERM=dumb to disable all color output.

BBCode Formatting

CJ's Shell supports BBCode-style formatting in prompts and output:

Tags: - [b]...[/b]: Bold text - [i]...[/i]: Italic text - [u]...[/u]: Underline text - [r]...[/r]: Reverse video - [color]...[/color]: Color names (e.g., [red], [blue]) - [#RRGGBB]...[/]: Hex RGB colors - [on color]...[/]: Background colors

Style Combinations: 

[b red on blue]Bold red text on blue background[/]
[i #ff00ff]Italic magenta text[/]

Advanced Features

Spell Correction

Automatic spell correction for commands and completions.

How It Works: When no exact match is found, cjsh attempts to find the closest match using edit distance algorithms.

Configuration: 

# Enable/disable spell correction (enabled by default)
cjshopt completion-spell on|off|status

Heredoc Support

Full editing capabilities when entering heredocs:

cat <<EOF
# You get full editing features here:
# - Syntax highlighting
# - Multiline editing
# - History access
# - All normal key bindings
EOF

Features: - Each line is edited with full isocline capabilities - Supports <<- (strip leading tabs) - Delimiter detection ends input - Ctrl+C/Ctrl+D cancels heredoc input

Readline Integration

CJ's Shell uses isocline's unified ic_readline() API for input, which provides:

Inline Right Text: Some prompts may display additional information on the right side of the input line (configured by themes).

Initial Input: Commands can pre-populate the input buffer (used by fc command for editing).

Special Return Values: - IC_READLINE_TOKEN_CTRL_C: Returned when Ctrl+C is pressed on empty buffer - IC_READLINE_TOKEN_CTRL_D: Returned when Ctrl+D is pressed on empty buffer (EOF)

Non-TTY Mode

When standard input is not a terminal (pipe, file redirect, debugger, etc.): - Line editing is disabled - Input is read directly from the stream - Prompts are still displayed but without styling - Scripts and pipes work seamlessly

Style Definitions

All visual aspects of the editor can be customized through style definitions.

Available Styles

Prompt Styles: - ic-prompt: Main prompt text - ic-linenumbers: Line numbers in multiline mode - ic-linenumber-current: Current line number highlight

Syntax Highlighting Styles: - ic-keyword: Shell keywords - ic-command: Valid commands - ic-error: Errors and invalid commands - ic-string: String literals - ic-comment: Comments - ic-operator: Operators - ic-variable: Variables - ic-number: Numbers - ic-bracket: Brackets - ic-bracket-match: Matching brackets

Editor Styles: - ic-hint: Inline hints - ic-selection: Selected text - ic-completion: Completion menu - ic-completion-selected: Selected completion

Style Syntax

cjshopt style_def <style-name> "<bbcode-style>"

Examples: 

# Make errors bright red and bold
cjshopt style_def ic-error "bold red"

# Use custom RGB color for commands
cjshopt style_def ic-command "#00ff00"

# Style keywords with italic blue
cjshopt style_def ic-keyword "italic blue"

# Combine multiple attributes
cjshopt style_def ic-string "italic #ffaa00"

Style Attributes: - Colors: red, blue, green, yellow, cyan, magenta, white, black - ANSI colors: ansi-red, ansi-bright-blue, etc. - RGB colors: #RRGGBB or #RGB - Attributes: bold, italic, underline, reverse - Background: on <color>

Configuration Examples

Complete Editing Configuration

Here's a comprehensive example for ~/.cjshrc:

# Multiline settings
cjshopt multiline on
cjshopt multiline-indent on
cjshopt line-numbers relative
cjshopt current-line-number-highlight on

# Completion settings
cjshopt completion-preview on
cjshopt auto-tab off
cjshopt completion-case off  # Case-insensitive completions
cjshopt completion-spell on

# Hint settings
cjshopt hint on
cjshopt hint-delay 100  # 100ms delay before showing hints

# Help settings
cjshopt inline-help on

# History
cjshopt set-history-max 10000

# Key bindings
cjshopt keybind profile set emacs

# Syntax highlighting styles
cjshopt style_def ic-keyword "bold blue"
cjshopt style_def ic-command "green"
cjshopt style_def ic-error "bold red"
cjshopt style_def ic-string "#ffaa00"
cjshopt style_def ic-comment "italic #888888"
cjshopt style_def ic-operator "bold"

Minimal Configuration

For a minimal, fast setup:

# Use the --minimal flag at startup, or configure selectively:
cjshopt multiline on
cjshopt line-numbers off
cjshopt completion-preview off
cjshopt hint off
cjshopt inline-help off

Performance Considerations

Optimization Tips

  1. Disable unnecessary features in resource-constrained environments
  2. Increase hint delay if experiencing lag while typing
  3. Reduce history size for faster search
  4. Use simpler themes to reduce prompt rendering time

Benchmarks

Isocline is designed to be fast and responsive: - Completion generation: < 10ms for typical cases - Syntax highlighting: Real-time with no noticeable lag - History search: Fast even with large history files - Multiline editing: Smooth for inputs up to hundreds of lines

Troubleshooting

Common Issues

Completions not working: - Check if completions are enabled (not started with --no-completions) - Verify PATH contains command directories - Check file permissions

Syntax highlighting not showing: - Ensure not started with --no-syntax-highlighting - Check terminal color support - Verify theme styles are defined

Key bindings not working: - Check terminal emulator key sending - Verify with cjshopt keybind list - Some terminals may not support all key combinations

Multiline issues: - Verify multiline is enabled: cjshopt multiline status - Check for terminal compatibility - Ensure terminal width is adequate

Getting Help

  • Press F1 during input for interactive help
  • Run cjshopt <subcommand> --help for command-specific help
  • Check logs in debug mode
  • Report issues on the CJsShell GitHub repository