lsv — A Three‑Pane Terminal File Viewer

lsv is a fast, curses‑based file viewer for the terminal. It presents three panes side by side:

• Parent: shows the contents of the parent directory of your current location.
• Current: shows the contents of the current directory with selection and navigation.
• Preview: shows a preview of the selected file (via a user‑defined preview command), or the entries of a selected directory.

The app is keyboard‑driven, configurable via Lua, and supports rich, ANSI‑colored previews from external tools (e.g., bat, glow).

Install

• From crates.io: cargo install lsv

Build & Run (from source)

• Build: cargo build
• Run: cargo run
• Optional trace logging: LSV_TRACE=1 LSV_TRACE_FILE=/tmp/lsv-trace.log cargo run

Navigation (defaults)

• Up/Down or k/j: move selection in the Current pane
• Right or Enter: enter selected directory
• Left or Backspace: go to parent directory (reselect the dir you just left)
• q or Esc: quit
• ?: toggle which‑key overlay (shows grouped keybindings)

Configuration Overview

lsv loads a Lua config from the first of:

1. $LSV_CONFIG_DIR/lua/init.lua
2. $XDG_CONFIG_HOME/lsv/lua/init.lua
3. ~/.config/lsv/lua/init.lua

Top‑level Lua API:

• lsv.config({ ... }): core settings (icons, keys, ui, etc.).
• lsv.set_previewer(function(ctx) ... end): return a shell command to render preview.
• lsv.map_action(key, description, function(lsv, config) ... end): bind keys to Lua functions.

Action helper functions available on lsv inside actions:

• lsv.select_item(index): set the current selection to index (0-based).
• lsv.select_last_item(): select the last item in the current list.
• lsv.quit(): request the app to exit.
• lsv.display_output(text, title?): show text in a bottom Output panel.
• lsv.os_run(cmd): run a shell command and show its captured output in the Output panel. Env includes LSV_PATH, LSV_DIR, LSV_NAME.

Context data passed to actions via config.context:

• cwd: current working directory.
• selected_index: current selection index (or a sentinel if none).
• current_len: number of items in the current list.

Minimal Example: Bind an external tool

-- Sample lsv config -- place in $HOME/.config/lsv/lua/init.lua
lsv.config({
  config_version = 1,
  keys = { sequence_timeout_ms = 0 },

  ui = {
    panes = { parent = 20, current = 30, preview = 50 },
    show_hidden = true,
    date_format = "%Y-%m-%d %H:%M",
    display_mode = "absolute",   -- or "friendly" (affects both dates and sizes)

    -- Optional row layout: icon/left/middle/right with placeholders
    row = {
      icon = "{icon} ",
      left = "{name}",
      middle = "",
      right = "{info}",
    },
  },
})

-- Safe shell quote helper
local function shquote(s)
  return "'" .. tostring(s):gsub("'", "'\\''") .. "'"
end

-- Example: bind "gs" to git status of the current directory
lsv.map_action("gs", "Git Status", function(lsv, config)
  local dir = (config.context and config.context.cwd) or "."
  lsv.os_run("git -C " .. shquote(dir) .. " status")
end)

-- Previewer function (ctx):
-- ctx = {
--   path       = absolute file path (string)
--   directory  = parent directory (string)
--   extension  = file extension without dot (string, may be empty)
--   is_binary  = boolean (simple heuristic)
--   height     = preview pane height in rows (number)
--   width      = preview pane width in columns (number)
--   preview_x  = top-left x of preview pane (number)
--   preview_y  = top-left y of preview pane (number)
-- }
-- Return a shell command string (placeholders are expanded: {path},{directory},{name},{extension}), or nil to use default head preview.
lsv.set_previewer(function(ctx)
	-- Render Markdown with glow, respecting pane width
	if ctx.extension == "md" or ctx.extension == "markdown" then
		-- You can build a command with placeholders:
		return "glow --style=dark --width=" .. tostring(ctx.width) .. " {path}"
	end

	if
		ctx.extension == "jpg"
		or ctx.extension == "jpeg"
		or ctx.extension == "png"
		or ctx.extension == "gif"
		or ctx.extension == "bmp"
		or ctx.extension == "tiff"
	then
		-- image preview using viu (needs installation)
		return "viu --width '{width}' --height '{height}' '{path}'"
	end
	-- For non-binary, colorize with bat (first 120 lines, no wrapping)
	if not ctx.is_binary then
		return "bat --color=always --style=numbers --paging=never --wrap=never --line-range=:120 {path}"
	end

	-- Fallback to default preview (first N lines)
	return nil
end)

Keybindings: Actions

• Bind with lsv.map_action(key, description, function(lsv, config) ... end).
• Prefer mutating config (e.g., config.ui.sort = "size") and using helpers like lsv.select_item(...).

Default action bindings

• Sorting: sn (by name), ss (by size), sr (toggle reverse)
• Info field: zn (none), zs (size), zc (created)
• Display mode: zf (friendly), za (absolute)
• Navigation: gg (top), G (bottom)
• Overlays: zm (toggle messages), zo (toggle last output), ? (which‑key)

Override example

-- Change the default for "ss" to also show sizes in the info column
lsv.map_action("ss", "Sort by size + show size", function(lsv, config)
  config.ui.sort = "size"
  config.ui.show = "size"
end)

Which‑Key Overlay and Sequences

• Type ? to toggle a bottom overlay listing available keys (uses descriptions).
• Composite sequences are supported (e.g., ss, zc). The overlay opens automatically when you type a registered prefix.
• Timeout: by default there is no timeout for multi‑key sequences (0).

  • To enable a timeout, set keys.sequence_timeout_ms in your Lua config:

    lsv.config({
      keys = { sequence_timeout_ms = 600 },  -- 600ms timeout for sequences
    })
    

Row Layout (icon/left/right)

Configure row sections under ui.row:

• Templates accept placeholders {icon}, {name}, {info}.
• Right column is right‑aligned, left is left‑aligned.

Rendering Modes and Formats

• Dates: display:absolute uses ui.date_format (default %Y-%m-%d %H:%M); display:friendly uses relative strings (e.g., 3d ago).
• Sizes: display:absolute shows raw bytes with B; display:friendly uses human units (KB/MB/...).

Placeholders (expanded in preview and commands)

• {path}: absolute file path
• {directory} (alias {dir}): parent directory
• {name}: basename of file
• {extension}: extension without dot
• {width}, {height}: preview pane size in characters
• {preview_x}, {preview_y}: preview pane top‑left coordinates
• $f: shorthand for {path}

Environment for external commands:

• LSV_PATH (selected file), LSV_DIR (directory), LSV_NAME (basename)

Preview Notes

• lsv captures the command’s output and renders ANSI colors (SGR). If your tool disables color when piped, add --color=always (bat) or set styles (glow). lsv sets FORCE_COLOR=1 and CLICOLOR_FORCE=1 for preview commands.
• For very large outputs, lsv trims to ui.preview_lines lines.

Tracing (debugging)

• Enable with LSV_TRACE=1 (default log path: $TMPDIR/lsv-trace.log or /tmp/lsv-trace.log).
• Override path with LSV_TRACE_FILE=/path/to/log.
• Logs include executed commands, exit codes, bytes written, and a snippet of preview output.

Status

• Legacy configuration methods are removed. Use the Lua APIs described above.
• Planned: robust MIME detection (optional), async preview.