Interactive Features

fortsh provides modern interactive features inspired by fish shell while maintaining POSIX compliance.

Source: src/io/readline.f90, src/io/syntax_highlight.f90, src/scripting/completion.f90

Topics

Line Editing - Cursor movement, text manipulation
History - Command history and search
Completion - Tab completion
Syntax Highlighting - Real-time command validation
Autosuggestions - Fish-style suggestions

Feature Overview

Feature	Description
Autosuggestions	History-based suggestions as you type
Syntax highlighting	Commands colored by validity
Fuzzy completion	Tab completion with fuzzy matching
Incremental search	Ctrl+R reverse history search
Vi mode	Optional Vi-style editing
FZF integration	Ctrl+F/H for file/history browsing

Keybinding Quick Reference

Cursor Movement

Key	Action
`Ctrl+A`	Beginning of line
`Ctrl+E`	End of line
`Ctrl+B`	Back one character
`Ctrl+F`	Forward one character
`Left/Right`	Move cursor
`Home/End`	Beginning/end of line

Editing

Key	Action
`Ctrl+D`	Delete character (or exit if empty)
`Ctrl+K`	Kill to end of line
`Ctrl+U`	Kill entire line
`Ctrl+W`	Kill previous word
`Ctrl+Y`	Yank (paste) killed text
`Ctrl+T`	Transpose characters
`Backspace`	Delete previous character

History

Key	Action
`Up/Down`	Previous/next history
`Ctrl+R`	Reverse incremental search
`Ctrl+S`	Forward incremental search
`Ctrl+G`	Cancel search

Completion & Suggestions

Key	Action
`Tab`	Complete command/file
`Right Arrow`	Accept autosuggestion
`Ctrl+F`	Accept autosuggestion (also FZF files)

Special

Key	Action
`Ctrl+L`	Clear screen
`Ctrl+C`	Cancel current line
`Ctrl+X`	Process kill mode

Editing Modes

Emacs Mode (Default)

Standard readline-style editing with the keybindings shown above.

Vi Mode

Enable with:

set -o vi

Insert mode (default after enabling):

Type normally
Esc to enter command mode

Command mode:

h/j/k/l - Movement
w/b/e - Word movement
0/$ - Beginning/end of line
x/X - Delete character
d+motion - Delete with motion
c+motion - Change with motion
y+motion - Yank with motion
p/P - Put after/before cursor
i/a/I/A - Enter insert mode
u - Undo
/+pattern - Forward search
?+pattern - Backward search
n/N - Next/previous match

Environment Variables

Variable	Purpose
`HISTFILE`	History file location (default: `~/.fortsh_history`)
`HISTSIZE`	Max history entries in memory (default: 1000)
`HISTFILESIZE`	Max history entries in file (default: 2000)
`HISTCONTROL`	History behavior: `ignoredups`, `ignorespace`, `erasedups`
`TERM`	Terminal type (affects highlighting)

Disabling Features

For scripts or testing:

# Disable autosuggestions
export FORTSH_NO_SUGGESTIONS=1

# Disable syntax highlighting
export FORTSH_NO_HIGHLIGHT=1

# Test mode (disables interactive features)
export FORTSH_TEST_MODE=1