lf/doc.go

//go:generate gen/docstring.sh

/*
lf is a terminal file manager.

Source code can be found in the repository at https://github.com/gokcehan/lf.

This documentation can either be read from terminal using "lf -doc" or online
at https://godoc.org/github.com/gokcehan/lf.

Reference

The following commands are provided by lf with default keybindings:

	up                (default "k" and "<up>")
	half-up           (default "<c-u>")
	page-up           (default "<c-b>")
	down              (default "j" and "<down>")
	half-down         (default "<c-d>")
	page-down         (default "<c-f>")
	updir             (default "h" and "<left>")
	open              (default "l" and "<right>")
	quit              (default "q")
	bot               (default "G")
	top               (default "gg")
	read              (default ":")
	read-shell        (default "$")
	read-shell-wait   (default "!")
	read-shell-async  (default "&")
	search            (default "/")
	search-back       (default "?")
	toggle            (default "<space>")
	invert            (default "v")
	yank              (default "y")
	clear             (default "c")
	delete            (default "d")
	put               (default "p")
	renew             (default "<c-l>")

The following commands are provided by lf without default keybindings:

	sync  synchronizes yanked/deleted files with server
	echo  prints its arguments to the message line
	cd    changes working directory to its argument
	push  simulate key pushes given in its argument

The following options can be used to customize the behavior of lf:

	dirfirst   bool    (default on)
	hidden     bool    (default off)
	preview    bool    (default on)
	scrolloff  int     (default 0)
	tabstop    int     (default 8)
	ifs        string  (default "") (not exported if empty)
	previewer  string  (default "") (not filtered if empty)
	shell      string  (default "$SHELL")
	showinfo   string  (default "none")
	sortby     string  (default "natural")
	timefmt    string  (default "Mon Jan _2 15:04:05 2006")
	ratios     string  (default "1:2:3")

The following variables are exported for shell commands:

	$f   current file
	$fs  marked file(s) separated with ':'
	$fx  current file or marked file(s) if any

Configuration

The configuration file should be located at:

	$XDG_CONFIG_HOME/lf/lfrc"

If "$XDG_CONFIG_HOME" is not set, it defaults to "$HOME/.config" so the
location should be:

	~/.config/lf/lfrc

A sample configuration file can be found at
https://github.com/gokcehan/lf/blob/master/etc/lfrc.example.

Prefixes

The following command prefixes are used by lf:

	:  read (default)    built-in command
	$  read-shell        shell command
	!  read-shell-wait   shell command waiting for key press
	&  read-shell-async  asynchronous shell command
	/  search            search file in current directory
	?  search-back       search file in the reverse order

The same evaluator is used for the command line and the configuration file. The
difference is that prefixes are not necessary in the command line. Instead
different modes are provided to read corresponding commands. Note that by
default these modes are mapped to the prefix keys above.

Syntax

Characters from "#" to "\n" are comments and ignored:

	# comments start with '#'

There are three special commands for configuration.

"set" is used to set an option which could be boolean, integer, or string:

	set hidden        # boolean on
	set nohidden      # boolean off
	set hidden!       # boolean toggle
	set scrolloff 10  # integer value
	set sortby time   # string value w/o quotes

"map" is used to bind a key to a command which could be built-in command,
custom command, or shell command:

	map gh cd ~       # built-in command
	map D trash       # custom command
	map i $less "$f"  # shell command
	map u !du -h .    # waiting shell command

You can delete an existing binding by leaving the expression empty:

	map gh            # deletes 'gh' mapping

"cmd" is used to define a custom command

	cmd usage $du -h . | less

You can delete an existing command by leaving the expression empty:

	cmd trash         # deletes trash command

If there is no prefix then ":" is assumed:

	map zt set showinfo time

An explicit ":" could be provided to group statements until a "\n" occurs which
is especially useful for "map" and "cmd" commands:

	map st :set sortby time; set showinfo time

If you need multiline you can wrap statements in "{{" and "}}" after the proper
prefix.

	map st :{{
		set sortby time
		set showinfo time
	}}

Mappings

The usual way to map a key sequence is to assign it to a named or unnamed
command. While this provides a clean way to remap builtin keys as well as other
commands, it can be limiting at times. For this reason "push" command is
provided by lf. This command is used to simulate key pushes given as its
arguments. You can "map" a key to a "push" command with an argument to create
various keybindings.

This is mainly useful for two purposes. First, it can be used to map a command
with a command count:

	map <c-j> push 10j

Second, it can be used to avoid typing the name when a command takes arguments:

	map r push :rename<space>

One thing to be careful is that since "push" command works with keys instead of
commands it is possible to accidentally create recursive bindings:

	map j push 2j

These types of bindings create a deadlock when executed.

Commands

For demonstration let us write a shell command to move selected file(s) to
trash.

A first attempt to write such a command may look like this:

	cmd trash ${{
		mkdir -p ~/.trash
		if [ -z $fs ]; then
			mv --backup=numbered "$f" $HOME/.trash
		else
			IFS=':'; mv --backup=numbered $fs $HOME/.trash
		fi
	}}

We check "$fs" to see if there are any marked files. Otherwise we just delete
the current file. Since this is such a common pattern, a separate "$fx"
variable is provided. We can use this variable to get rid of the conditional:

	cmd trash ${{
		mkdir -p ~/.trash
		IFS=':'; mv --backup=numbered $fx $HOME/.trash
	}}

The trash directory is checked each time the command is executed. We can move
it outside of the command so it would only run once at startup:

	${{ mkdir -p ~/.trash }}

	cmd trash ${{ IFS=':'; mv --backup=numbered $fx $HOME/.trash }}

Since these are one liners, we can drop "{{" and "}}":

	$mkdir -p ~/.trash

	cmd trash $IFS=':'; mv --backup=numbered $fx $HOME/.trash

Finally note that we set "IFS" variable accordingly in the command. Instead we
could use the "ifs" option to set it for all commands (e.g. "set ifs ':'").
This could be especially useful for interactive use (e.g. "rm $fs" would simply
work). This option is not set by default as things may behave unexpectedly at
other places.

File Operations

lf uses the underlying "cp" and "mv" shell commands for file operations. For
this purpose, when you "yank" (i.e. copy) a file, it doesn't actually copy the
file on the disk, but only records its name to memory. The actual file
operation takes place when you do the "put" in which case the "cp" command is
used. Similarly the "mv" command is used for "delete" (i.e. cut or kill)
followed by "put". These traditional names (e.g. "yank", "delete", and "put")
are picked instead of the other common convention (e.g. copy and cut) to
resemble the default keybinds for these operations.

Opening Files

You can use "open-file" command to open a file. This is a special command
called by "open" when the current file is not a directory. Normally a user maps
the "open" command to a key (default "l") and customize "open-file" command as
desired. You can define it just as you would define any other command:

	cmd open-file $IFS=':'; vim $fx

It is possible to use different command types:

	cmd open-file &xdg-open "$f"

You may want to use either file extensions or mime types from "file" command:

	cmd open-file ${{
		case $(file --mime-type "$f" -b) in
			text/*) IFS=':'; vim $fx;;
			*) IFS=':'; for f in $fx; do xdg-open "$f" &> /dev/null & done;;
		esac
	}}

lf does not come bundled with a file opener. You can use any of the existing
file openers as you like. Possible options are "open" (for Mac OS X only),
"xdg-utils" (executable name is "xdg-open"), "libfile-mimeinfo-perl"
(executable name is "mimeopen"), "rifle" (ranger's default file opener), or
"mimeo" to name a few.

Previewing Files

lf previews files on the preview pane by printing the file until the end or the
preview pane is filled. This output can be enhanced by providing a custom
preview script for filtering. This can be used to highlight source codes, list
contents of archive files or view pdf or image files as text to name few. For
coloring lf recognizes ansi escape codes.

In order to use this feature you need to set the value of "previewer" option to
the path of an executable file. lf passes the current file name as the first
argument and the height of the preview pane as the second argument when running
this file. Output of the execution is printed in the preview pane. You may want
to use the same script in your pager mapping as well if any:

	set previewer ~/.config/lf/pv.sh
	map i $~/.config/lf/pv.sh "$f" | less -R

Since this script is called for each file selection change it needs to be as
efficient as possible and this responsibility is left to the user. You may use
file extensions to determine the type of file more efficiently compared to
obtaining mime types from "file" command. Extensions can then be used to match
cleanly within a conditional:

	#!/bin/sh

	case "$1" in
		*.tar*) tar tf "$1";;
		*.zip) unzip -l "$1";;
		*.rar) unrar l "$1";;
		*.7z) 7z l "$1";;
		*.pdf) pdftotext "$1" -;;
		*) highlight -O ansi "$1" || cat "$1";;
	esac

Another important consideration for efficiency is the use of programs with
short startup times for preview. For this reason, "highlight" is recommended
over "pygmentize" for syntax highlighting. Besides, it is also important that
the application is processing the file on the fly rather than first reading it
to the memory and then do the processing afterwards. This is especially
relevant for big files. lf automatically closes the previewer script output
pipe with a SIGPIPE when enough lines are read. When everything else fails, you
can make use of the height argument to only feed the first portion of the file
to a program for preview.
*/
package main