Cheap cheat trick

July 2nd, 2021
cheatsheetsfzf

Cheap cheat trick

Poker hand with five aces

Recently I came across a glorious list of modern command-line tools. One of those tools is cheat a little system to save and retrieve little snippets of code from the command-line.

My first reaction was “Neat!”, because it is. Then I thought “wait, I already have something like that. Kind of.”

What I have is a private cheatsheet wiki, aka a directory full of Markdown files. The fact that the Markdown files are free-form text is, for me, preferable to the more restricted format of cheat, which is one snippet per file. But I can see the allure of quickly finding a snippet via tags, and to access it via the command-line. Mostly for snippets pertaining to command-line matters like docket commands, or tar recipes.

The question becomes… can I shoehorn the command-line behavior of cheat to work with my Markdown wiki? Let’s find out!

Defining the markup of a cheat

First thing to do is to find a way to identify cheat items in the Markdown files.

Since those cheatsheets are usually copy’n’paste of commands I find and want to remember, they are typically terse:

# Docker

# Misc commands

launch daemon:

    sudo dockerg -g /home/docker

list images:

    docker images

remove image from machine:

    docker image rm _image_id_

To keep it uncomplicated, why not use backtick-delimited code blocks, and add a label cheat: as part of the opening backtick? I.e.:

    # Docker

    # Misc commands

    ```cheat: launch daemon
    sudo dockerg -g /home/docker
    ```

    ```cheat: list images     @image
    docker images
    ```

    ```cheat: remove image from machine    @image
    docker image rm _image_id_
    ```

That ain’t bad. It’s still legible, has only marginally more markup, and we can declare that everything after the cheat: is the short description of that snippet. As you see, I added optional @tags at the end of the description, that’s to help with searching down the line.

And if that Markdown was being processed by something that highlights code, we didn’t rob ourselves of that. Having a first line looking like the following would (should?) totally work:


    ```javascript cheat: invert keys/values of object
    inverted = Object.fromEntries( 
        Object.entries(original)
            .map(([k,v]) => [ v, k ]) 
    )
    ```

Find those cheats

So we have cheats embedded in Markdown files. Great, now how to we find them? With the might of grep, of course! Or, in this case, its younger relative, rg:

$ rg '^```.*cheat:' $CHEATSHEETS_DIR --no-heading | cat

/home/yanick/vimwiki/cheatsheets/docker.md:``` cheat: Launch the deamon @init
/home/yanick/vimwiki/cheatsheets/docker.md:```cheat: remove image from machine
/home/yanick/vimwiki/cheatsheets/svelte.md:```cheat: comment
/home/yanick/vimwiki/cheatsheets/svelte.md:```cheat: if

Woo! We have them. But those lines are a little long. Let’s cut the bits that don’t give us any valuable info:

⥼ rg '^```.*cheat:' $CHEATSHEETS_DIR --no-heading \
    | perl -pe's#$ENV{CHEATSHEETS_DIR}##;'        \
            -e's#```.*?cheat:##;s#.md##' 

docker: Launch the deamon @init
docker: remove image from machine
svelte: comment
svelte: if

Yeah, that will do it.

Select the cheat

Since our goal is to show a specific cheat, let’s bring in fzf into the mix. And here’s the magic: fzf allow to have custom previews of the selected item, so let’s be wild and have:

rg '^```.*cheat:' $CHEATSHEETS_DIR --no-heading \
    | perl -pe's#$ENV{CHEATSHEETS_DIR}##;' \
            -e's#```.*?cheat:##;s#.md##' \
    | fzf --preview="cheat-preview.pl {}" 

with cheat-preview.pl being:

my( $file, $text ) = split /:s*/, shift, 2;

open my $fh, "<", $ENV{CHEATSHEETS_DIR}."/$file.md"
    or die $!;

my $line = 0;

while(<$fh>) {
    next unless /cheat:s*Q$text/.../```/;

    exit if /^```$/;

    print;
}

And that’s give us

screenshot of fzf with listing of cheats

This is getting nice.

Display the cheat

Once the cheat has been selected, all that is left to do is to print it to the console. And since chances are we’ll want to use it, why not copy it to the clipboard (minus the title) while we are at it?

In the Fish shell, assuming the cheat text is captured in $cheat, that would look like:

set_color red; echo -e "\n" $cheat[1] "\n"; set_color normal;

set -l cheat ( string join '\n' $cheat[2..-1] )

echo -e $cheat

echo -e $cheat | xclip -selection clipboard

Putting it all together

Assembling those parts together, we have the following fish script (also available here):

#!/usr/bin/env fish

function cheat

    if test -z $CHEATSHEETS_DIR
        echo "CHEATSHEETS_DIR is not defined"
        return 1
    end

    set -l command $argv[1]

    if test "$command" = 'get'
        _cheat_get $argv[2..-1]
    else if test "$command" = 'list'
        _cheat_list
    else
        _cheat_query $argv
    end

end

function _cheat_list
    rg '^```.*cheat:' $CHEATSHEETS_DIR --no-heading         | perl -pe's#$ENV{CHEATSHEETS_DIR}##;' 
                -e's#```.*?cheat:##;s#.md##'
end

function _cheat_query

    set -l query ""

    if test (count $argv) -gt 0
        set query ( string join " " $argv )
    end

    set -l selection ( 
        cheat list 
            | fzf --preview="cheat get {}" -q $query 
    )

    set -l cheat (cheat get $selection | string trim -c " \n")

    set_color red; echo -e "\n" $cheat[1] "\n"; set_color normal;

    set -l cheat ( string join '\n' $cheat[2..-1] )

    echo -e $cheat

    echo -e $cheat | xclip -selection clipboard

end

function _cheat_get

    perl -e '
my( $file, $text ) = split /:s*/, shift, 2;

open my $fh, "<", $ENV{CHEATSHEETS_DIR}."/$file.md"
    or die $!;

my $line = 0;

while(<$fh>) {
    next unless /cheat:s*Q$text/.../```/;

    exit if /^```$/;

    print;
}
' $argv

end

cheat $argv

And using it looks like this:

Seen a typo or an error? Submit an edit on GitHub!