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')
    top          (default 'gg')
    bottom       (default 'G')
    toggle       (default '<space>')
    invert       (default 'v')
    unmark       (default 'u')
    yank         (default 'y')
    delete       (default 'd')
    put          (default 'p')
    clear        (default 'c')
    redraw       (default '<c-l>')
    reload       (default '<c-r>')
    read         (default ':')
    shell        (default '$')
    shell-pipe   (default '%')
    shell-wait   (default '!')
    shell-async  (default '&')
    search       (default '/')
    search-back  (default '?')
    search-next  (default 'n')
    search-prev  (default 'N')

The following commands are provided by lf without default keybindings:

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

The following command line commands are provided by lf with default
keybindings:

    cmd-escape            (default '<esc>')
    cmd-complete          (default '<tab>')
    cmd-enter             (default '<c-j>' and '<enter>')
    cmd-history-next      (default '<c-n>')
    cmd-history-prev      (default '<c-p>')
    cmd-delete            (default '<c-d>' and '<delete>')
    cmd-delete-back       (default '<bs>' and '<bs2>')
    cmd-left              (default '<c-b>' and '<left>')
    cmd-right             (default '<c-f>' and '<right>')
    cmd-home              (default '<c-a>' and '<home>')
    cmd-end               (default '<c-e>' and '<end>')
    cmd-delete-home       (default '<c-u>')
    cmd-delete-end        (default '<c-k>')
    cmd-delete-unix-word  (default '<c-w>')
    cmd-yank              (default '<c-y>')
    cmd-transpose         (default '<c-t>')
    cmd-interrupt         (default '<c-c>')
    cmd-word              (default '<a-f>')
    cmd-word-back         (default '<a-b>')
    cmd-capitalize-word   (default '<a-c>')
    cmd-delete-word       (default '<a-d>')
    cmd-uppercase-word    (default '<a-u>')
    cmd-lowercase-word    (default '<a-l>')
    cmd-transpose-word    (default '<a-t>')

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

    dircounts   boolean  (default off)
    dirfirst    boolean  (default on)
    drawbox     boolean  (default off)
    globsearch  boolean  (default off)
    hidden      boolean  (default off)
    ignorecase  boolean  (default on)
    preview     boolean  (default on)
    reverse     boolean  (default off)
    smartcase   boolean  (default on)
    wrapscan    boolean  (default on)
    scrolloff   integer  (default 0)
    tabstop     integer  (default 8)
    filesep     string   (default "\n")
    ifs         string   (default '') (not exported if empty)
    previewer   string   (default '') (not filtered if empty)
    promptfmt   string   (default "\033[32;1m%u@%h\033[0m:\033[34;1m%w/\033[0m\033[1m%f\033[0m")
    shell       string   (default 'sh')
    sortby      string   (default 'natural')
    timefmt     string   (default 'Mon Jan _2 15:04:05 2006')
    ratios      string   (default '1:2:3')
    info        string   (default '')

The following variables are exported for shell commands:

    $f   current file
    $fs  marked file(s) separated with 'filesep'
    $fx  current file or marked file(s) if any
    $id  id number of the client

The following additional keybindings are provided by default:

    map zh set hidden!
    map zr set reverse!
    map zn set info
    map zs set info size
    map zt set info time
    map za set info size:time
    map sn :set sortby natural; set info
    map ss :set sortby size; set info size
    map st :set sortby time; set info time
    map gh cd ~

The following keybindings to applications are provided by default on unix:

    map e $$EDITOR $f ('vi' if empty)
    map i $$PAGER $f  ('less' if empty)
    map w $$SHELL     ('sh' if empty)

The following keybindings to applications are provided by default on windows:

    map e $notepad %f%
    map i $more %f%
    map w $cmd

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)  builtin/custom command
    $  shell           shell command
    %  shell-pipe      shell command running with the ui
    !  shell-wait      shell command waiting for key press
    &  shell-async     shell command running asynchronously
    /  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 for
read and shell commands. The difference is that prefixes are not necessary in
the command line. Instead, different modes are provided to read corresponding
commands. These modes are mapped to the prefix keys above by default. Searching
commands are only used from the command line.

Syntax

Characters from '#' to newline are comments and ignored:

    # comments start with '#'

There are three special commands ('set', 'map', and 'cmd') and their variants
for configuration.

'set' is used to set an option which can 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
    set sortby 'time'  # string value with single quotes (whitespaces)
    set sortby "time"  # string value with double quotes (backslash escapes)

'map' is used to bind a key to a command which can be builtin command, custom
command, or shell command:

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

'cmap' is used to bind a key to a command line command which can only be one of
the builtin commands:

    cmap <c-g> cmd-escape

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

    map gh             # deletes 'gh' mapping
    cmap <c-g>         # deletes '<c-g>' 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 info time

An explicit ':' can be provided to group statements until a newline which is
especially useful for 'map' and 'cmd' commands:

    map st :set sortby time; set info time

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

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

Key Mappings

Regular keys are assigned to a command with the usual syntax:

    map a down

Keys combined with the shift key simply use the uppercase letter:

    map A down

Special keys are written in between '<' and '>' characters and always use
lowercase letters:

    map <enter> down

Angle brackets can be assigned with their special names:

    map <lt> down
    map <gt> down

Function keys are prefixed with 'f' character:

    map <f-1> down

Keys combined with the control key are prefixed with 'c' character:

    map <c-a> down

Keys combined with the alt key are assigned in two different ways depending on
the behavior of your terminal. Older terminals (e.g. xterm) may set the 8th bit
of a character when the alt key is pressed. On these terminals, you can use the
corresponding byte for the mapping:

    map á down

Newer terminals (e.g. gnome-terminal) may prefix the key with an escape key
when the alt key is pressed. lf uses the escape delaying mechanism to recognize
alt keys in these terminals (delay is 100ms). On these terminals, keys combined
with the alt key are prefixed with 'a' character:

    map <a-a> down

Please note that, some key combinations are not possible due to the way
terminals work (e.g. control and h combination sends a backspace key instead).
The easiest way to find the name of a key combination is to press the key while
lf is running and read the name of the key from the unknown mapping error.

Push 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.

Shell Commands

Regular shell commands are the most basic command type that is useful for many
purposes. For example, we can 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 "$f" ~/.trash
        else
            IFS="`printf '\n\t'`"; mv $fs ~/.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="`printf '\n\t'`"; mv $fx ~/.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="`printf '\n\t'`"; mv $fx ~/.trash }}

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

    $mkdir -p ~/.trash

    cmd trash $IFS="`printf '\n\t'`"; mv $fx ~/.trash

Finally note that we set 'IFS' variable manually in these commands. Instead we
could use the 'ifs' option to set it for all shell commands (i.e. 'set ifs
"\n"'). This can be especially useful for interactive use (e.g. '$rm $f' or
'$rm $fs' would simply work). This option is not set by default as it can
behave unexpectedly for new users. However, use of this option is highly
recommended and it is assumed in the rest of the documentation.

Piping Shell Commands

Regular shell commands have some limitations in some cases. When an output or
error message is given and the command exits afterwards, the ui is immediately
resumed and there is no way to see the message without dropping to shell again.
Also, even when there is no output or error, the ui still needs to be paused
while the command is running. This can cause flickering on the screen for short
commands and similar distractions for longer commands.

Instead of pausing the ui, piping shell commands connects stdin, stdout, and
stderr of the command to the statline in the bottom of the ui. This can be
useful for programs following the unix philosophy to give no output in the
success case, and brief error messages or prompts in other cases.

For example, following rename command prompts for overwrite in the statline if
there is an existing file with the given name:

    cmd rename %mv -i $f $1

You can also output error messages in the command and it will show up in the
statline. For example, an alternative rename command may look like this:

    cmd rename %[ -e $1 ] && printf "file exists" || mv $f $1

One thing to be careful is that although input is still line buffered, output
and error are byte buffered and verbose commands will be very slow to display.

Waiting Shell Commands

Waiting shell commands are similar to regular shell commands except that they
wait for a key press when the command is finished. These can be useful to see
the output of a program before the ui is resumed. Waiting shell commands are
more appropriate than piping shell commands when the command is verbose and the
output is best displayed as multiline.

Asynchronous Shell Commands

Asynchronous shell commands are used to start a command in the background and
then resume operation without waiting for the command to finish. Stdin, stdout,
and stderr of the command is neither connected to the terminal nor to the ui.

Remote Commands

One of the more advanced features in lf is remote commands. All clients connect
to a server on startup. It is possible to send commands to all or any of the
connected clients over the common server. This is used internally to notify
file selection changes to other clients.

To use this feature, you need to use a client which supports communicating with
a UNIX-domain socket. OpenBSD implementation of netcat (nc) is one such
example. You can use it to send a command to the socket file:

    echo 'send echo hello world' | nc -U /tmp/lf.${USER}.sock

Since such a client may not be available everywhere, lf comes bundled with a
command line flag to be used as such. When using lf, you do not need to specify
the address of the socket file. This is the recommended way of using remote
commands since it is shorter and immune to socket file address changes:

    lf -remote 'send echo hello world'

In this command 'send' is used to send the rest of the string as a command to
all connected clients. You can optionally give it an id number to send a
command to a single client:

    lf -remote 'send 1000 echo hello world'

All clients have a unique id number but you may not be aware of the id number
when you are writing a command. For this purpose, an '$id' variable is exported
to the environment for shell commands. You can use it to send a remote command
from a client to the server which in return sends a command back to itself. So
now you can display a message in the current client by calling the following in
a shell command:

    lf -remote "send $id echo hello world"

Since lf does not have control flow syntax, remote commands are used for such
needs. For example, you can configure the number of columns in the ui with
respect to the terminal width as follows:

    cmd recol ${{
        w=$(tput cols)
        if [ $w -le 80 ]; then
            lf -remote "send $id set ratios 1:2"
        elif [ $w -le 160 ]; then
            lf -remote "send $id set ratios 1:2:3"
        else
            lf -remote "send $id set ratios 1:2:3:5"
        fi
    }}

Besides 'send' command, there are also two commands to get or set the current
file selection. Two possible modes 'copy' and 'move' specify whether selected
files are to be copied or moved. File names are separated by newline character.
Setting the file selection is done with 'save' command:

    lf -remote "$(printf 'save\ncopy\nfoo.txt\nbar.txt\nbaz.txt\n')"

Getting the file selection is similarly done with 'load' command:

    resp=$(lf -remote 'load')
    mode=$(echo "$resp" | sed -n '1p')
    list=$(echo "$resp" | sed '1d')
    if [ $mode = 'copy' ]; then
        # do something with $list
    elif [ $mode = 'move' ]; then
        # do something else with $list
    fi

Lastly, there is a 'conn' command to connect the server as a client. This
should not be needed for users.

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.

You can customize these operations by defining a 'put' command. This is a
special command that is called when it is defined instead of the builtin
implementation. The default behavior is similar to the following command:

    cmd put ${{
        load=$(lf -remote 'load')
        mode=$(echo "$load" | sed -n '1p')
        list=$(echo "$load" | sed '1d')
        if [ $mode = 'copy' ]; then
            cp -R -n $list .
        elif [ $mode = 'move' ]; then
            mv -n $list .
        fi
        lf -remote "send $id reload"
        lf -remote "$(printf 'save\nmove\n\n')"
        lf -remote "send sync"
    }}

Some useful things are to use the backup option ('--backup') with 'cp' and 'mv'
commands if they support it (i.e. GNU implementation), change the command type
to asynchronous, or use 'rsync' command with progress bar option for copying
and feed the progress to the client periodically with remote 'echo' calls.

By default, lf does not provide an actual file deletion command to protect new
users. You can define such a command and optionally assign a key if you like.
An example command to move selected files to a trash folder and remove files
completely are provided in the example configuration file.

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 $vi $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/*) vi $fx;;
            *) for f in $fx; do xdg-open $f > /dev/null 2> /dev/null & done;;
        esac
    }}

Following commands are provided by default:

    cmd open-file &start %f%      # windows
    cmd open-file &open "$f"      # mac
    cmd open-file &xdg-open "$f"  # others

You may also use any other existing file openers as you like. Possible options
are '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.

Colorschemes

lf tries to automatically adapt its colors to the environment. On startup,
first '$LS_COLORS' environment variable is checked. This variable is used by
GNU ls to configure its colors based on file types and extensions. The value of
this variable is often set by GNU dircolors in a shell configuration file.
dircolors program itself can be configured with a configuration file. dircolors
supports 256 colors along with common attributes such as bold and underline.

If '$LS_COLORS' variable is not set, '$LSCOLORS' variable is checked instead.
This variable is used by ls programs on unix systems such as Mac and BSDs. This
variable has a simple syntax and supports 8 colors and bold attribute.

If both of these environment variables are not set, then lf fallbacks to its
default colorscheme. Default lf colors are taken from GNU dircolors defaults.
These defaults use 8 basic colors and bold attribute.

Keeping this mechanism in mind, you can configure lf colors in two different
ways. First, you can configure 8 basic colors used by your terminal and lf
should pick up those colors automatically. Depending on your terminal, you
should be able to select your colors from a 24-bit palette. This is the
recommended approach as colors used by other programs will also match each
other.

Second, you can set the values of environmental variables mentioned above for
fine grained customization. This is useful to change colors used for different
file types and extensions. '$LS_COLORS' is more powerful than '$LSCOLORS' and
it can be used even when GNU programs are not installed on the system. You can
combine this second method with the first method for best results.
*/
package main