Line Editing

fortsh provides comprehensive line editing with both Emacs and Vi modes.

Source: src/io/readline.f90:42-62, 2042-2320

Editing Modes

Emacs Mode (Default)

Most users are familiar with Emacs-style keybindings:

set -o emacs   # Enable (default)

Vi Mode

For vi/vim users:

set -o vi      # Enable vi mode

Vi mode has two states:

Insert mode - Normal text input
Command mode - Navigation and editing (press ESC)

Emacs Keybindings

Cursor Movement

Key	Action
`Ctrl+A`	Beginning of line
`Ctrl+E`	End of line
`Ctrl+B`	Back one character
`Ctrl+F`	Forward one character
`Alt+B`	Back one word
`Alt+F`	Forward one word

Editing

Key	Action
`Ctrl+D`	Delete character at cursor (or EOF if empty)
`Backspace`	Delete character before cursor
`Ctrl+K`	Kill (cut) to end of line
`Ctrl+U`	Kill entire line
`Ctrl+W`	Kill previous word
`Alt+D`	Kill next word
`Ctrl+Y`	Yank (paste) killed text
`Ctrl+T`	Transpose characters
`Alt+T`	Transpose words

History

Key	Action
`Up` / `Ctrl+P`	Previous history entry
`Down` / `Ctrl+N`	Next history entry
`Ctrl+R`	Reverse incremental search
`Ctrl+S`	Forward incremental search
`Alt+<`	First history entry
`Alt+>`	Last history entry

Control

Key	Action
`Ctrl+C`	Cancel current input
`Ctrl+G`	Abort (cancel search/operation)
`Ctrl+L`	Clear screen
`Ctrl+Z`	Suspend shell

fortsh-Specific

Key	Action
`Ctrl+H`	FZF history browser
`Ctrl+F`	FZF file browser
`Ctrl+X`	Process kill mode

Vi Mode

Switching Modes

ESC - Enter command mode
i, a, I, A, etc. - Enter insert mode

Insert Mode Commands

Key	Action
`i`	Insert before cursor
`a`	Insert after cursor
`I`	Insert at beginning of line
`A`	Insert at end of line
`o`	Open line below
`O`	Open line above

Command Mode Navigation

Key	Action
`h`	Move left
`l`	Move right
`0`	Beginning of line
`$`	End of line
`w`	Next word
`b`	Previous word
`e`	End of word
`j`	History down
`k`	History up

Command Mode Editing

Key	Action
`x`	Delete character at cursor
`X`	Delete character before cursor
`dw`	Delete word
`dd`	Delete entire line
`d$`	Delete to end of line
`d0`	Delete to beginning
`cw`	Change word
`cc`	Change entire line
`r`	Replace character
`R`	Replace mode

Vi Repeat Counts

Commands can be prefixed with a count:

3w     # Move 3 words forward
5x     # Delete 5 characters
2dd    # Delete 2 lines

Vi Marks

Set and jump to positions:

ma - Set mark 'a' at current position
`a - Jump to mark 'a'
'a - Jump to beginning of line with mark 'a'

Vi Search

/pattern - Search forward
?pattern - Search backward
n - Next match
N - Previous match

Incremental Search

Reverse Search (Ctrl+R)

Search backward through history:

(reverse-i-search)`git': git commit -m "fix bug"

Type characters to narrow search
Ctrl+R again: next match
Ctrl+S: switch to forward search
Enter: accept result
Ctrl+G: cancel

Forward Search (Ctrl+S)

Search forward through history:

(i-search)`make': make clean

Note: Ctrl+S may be intercepted by terminal flow control. Disable with:

stty -ixon

Kill Ring

Text cut with Ctrl+K, Ctrl+U, Ctrl+W, etc. is saved to the kill ring.

Ctrl+Y - Paste most recent kill
Alt+Y - Cycle through kill ring (after Ctrl+Y)

Word Movement

Word boundaries depend on character class:

Alphanumeric characters and underscores form words
Punctuation and whitespace separate words

# Cursor positions marked with |
path=/usr/local/bin
     |   |     |    # Word boundaries

Implementation Details

State Management

Line editing state is managed by input_state_t (readline.f90:112-199):

type :: input_state_t
  character(len=MAX_LINE_LEN) :: buffer
  integer :: cursor_pos           ! 0-based
  integer :: editing_mode         ! EMACS or VI
  integer :: vi_mode              ! INSERT or COMMAND
  character(len=64) :: vi_command_buffer
  integer :: vi_marks(26)         ! Marks a-z
  logical :: dirty                ! Needs redraw
end type

Mode Constants

integer, parameter :: EDITING_MODE_EMACS = 1
integer, parameter :: EDITING_MODE_VI = 2
integer, parameter :: VI_MODE_INSERT = 1
integer, parameter :: VI_MODE_COMMAND = 2

Source: readline.f90:93-97

Configuration

inputrc

Create ~/.inputrc for readline configuration:

# Vi mode by default
set editing-mode vi

# Show mode in prompt
set show-mode-in-prompt on

# Case-insensitive completion
set completion-ignore-case on

Shell Options

# Switch to vi mode
set -o vi

# Switch back to emacs mode
set -o emacs