Notes, notes and notes

Notes about things I learn, things I do, things I want to remember, but never do. You can subscribe to this RSS feed which contains only the notes without the blog posts.

Bulk thumbnails

Sunday Jun 4, 2023 with tags ( bash )

Make bulk thumbnails of JPGs with ImageMagick.

#!/bin/bash

directory="./images/"
dimensions="360x360"

for file in "$directory"*.jpg; do
  convert "$file" -resize $dimensions "$file" "${file%.*}-thumbnail.jpg"
done

Edsger W. Dijkstra Manuscripts ebook

Thursday Jun 1, 2023

I love reading the original manuscripts of Edsger W. Dijkstra. They are available online at the University of Texas at Austin website, but I also found MOBI version. I converted it into ePub as well.

Downloads:

Sources and credits:

Stream chill radio

Thursday Jun 1, 2023 with tags ( audio )

Just click play to listen to the stream.

Source: https://ambientmodern.com

Extending dte editor

Wednesday May 31, 2023 with tags ( dte )

dte is an interesting editor I started using lately more and more. Since it is using execvp() it can be easily extended. I needed comment/uncomment feature so I created a small utility that does this for me. Code lives on repository dte extensions but this utilities can be used for whatever you want. Make sure you have version 1.11 or above.

Next one will be invoking formatter based on the type of a file.

My config that works for me.

set show-line-numbers true;
set tab-width 4;
set case-sensitive-search false;

# Special aliases
alias m_comment 'exec -s -i line -o buffer -e errmsg ~/.dte/bin/comment'
alias m_format 'save; exec go fmt .; reload'
alias m_duplicate 'copy;paste';

# Useful aliases.
alias m_force_close 'quit -f';
alias m_reload 'close; open $FILE'

# Key bindings.
bind M-s save;
bind M-q m_force_close;
bind M-z refresh;
bind C-down blkdown;
bind C-up blkup;
bind C-_ m_comment;
bind M-. m_format;
bind C-d m_duplicate;

# Syntax highlighting.
hi preproc magenta;
hi keyword red;
hi linenumber blue;
hi comment cyan;

Grep to Less that maintain colors

Monday May 29, 2023 with tags ( bash )

I often use grep to search for todo’s in my code and other people’s code and then pipe them in less and I missed having colors that grep outputs in less.

Grep’s --color=always use markers to highlight the matching strings.
Less’s -R option outputs “raw” control characters.

You could use alias grep='grep --color=always' and alias less='less -R' or create todo function in your .bashrc that accepts first argument as search string.

# This is where the magic happens.
grep --color=always -rni "TODO:" | less -R

Easy measure time took in a bash script

Sunday May 28, 2023 with tags ( bash )

In Bash, the $SECONDS variable is a special variable that automatically keeps track of the number of seconds since the current shell or script started executing. It starts counting from the moment the script begins running.

#!/bin/bash

# Reset the timer to zero.
SECONDS=0

# Do something.
sleep 5

# Print the time elapsed.
echo "Time taken: $SECONDS seconds"

Make DCSS playable on 4k displays

Saturday May 27, 2023 with tags ( dcss )

Dungeon Crawl Stone Soup has a a very small font by default. On a 4k display, it is barely readable. This is how I made it playable.

Make a file ~/.crawlrc with the following content:

# Adjust the sizes to your liking.

tile_font_crt_size = 32
tile_font_stat_size = 32
tile_font_msg_size = 32
tile_font_tip_size = 32
tile_font_lbl_size = 32
tile_sidebar_pixels = 64

To zoom in and out in viewport, press Ctrl+ and Ctrl- respectively.

All the possible options are documented in the Dungeon Crawl Stone Soup Options Guide file.

Drawing Pixels in Plan9

Saturday May 27, 2023 with tags ( plan9 graphics )

I have started exploring Plan9’s graphics capabilities. This is a hello world alternative for drawing that draws a yellow square on a blue background.

More information:

draw.h header file contains all the drawing functions
draw man page has a bit more digestable descriptions of the draw functions
graphics man page has a bit more digestable descriptions of the graphics functions
all man pages can be a valuable resource for learning about the system

// main.c
#include <u.h>
#include <libc.h>
#include <draw.h>
#include <cursor.h>

void
main()
{
  ulong co;
  Image *im, *bg;
  co = 0x0000FFFF;

  if (initdraw(nil, nil, argv0) < 0)
  {
    sysfatal("%s: %r", argv0);
  }

  im = allocimage(display, Rect(0, 0, 300, 300), RGB24, 0, DYellow);
  bg = allocimage(display, Rect(0, 0, 1, 1), RGB24, 1, co);

  if (im == nil || bg == nil)
  {
    sysfatal("not enough memory");
  }

  draw(screen, screen->r, bg, nil, ZP);
  draw(screen, screen->r, im, nil, Pt(-40, -40));

  flushimage(display, Refnone);

  // Wait 10 seconds before exiting.
  sleep(10000);

  exits(nil);
}

And then compile with mk (mkfile below):

# mkfile
</$objtype/mkfile

RC=/rc/bin
BIN=/$objtype/bin
MAN=/sys/man

main:
	$CC $CFLAGS main.c
	$LD $LDFLAGS -o main main.$O

And run with ./main. To exit the program, press Delete key (strange but this is the alternative for Ctrl+C).

This is very cool indeed!

Cronjobs on Github with Github Actions

Saturday May 27, 2023 with tags ( github )

In the root of your repository create a folder .github/workflows and in that folder create a file a file cron.yaml. This file can be named whatever you wish. But it has to be a yaml file.

File below (.github/workflows/cron.yaml) describes an action that will trigger every six hours and it will curl example.com.

However. Be sure that you have enough credits. Free account is not that generous with the minutes they give you for free. Check more about GitHub Actions usage on their website https://docs.github.com/en/actions.

# .github/workflows/cron.yaml
name: Do a curl every 6 hours
on:
  schedule:
    - cron: '0 */6 * * *'
jobs:
  cron:
    runs-on: ubuntu-latest
    steps:
      - name: Call some url
        run: curl 'https://example.com'

Dungeon Crawl Stone Soup - New player guide

Thursday May 25, 2023 with tags ( dcss )

An amazing game deserves an amazing guide. All this material can be find in some form on another on craw’s official repository.

DCSS Quickstart - Very short introduction to the game
DCSS Manual - Extensive manual about the game

Movement and Exploration

You can move around with the numpad (try numlock on and off), vi-keys, or clicking with the mouse. Arrow keys work, though you can’t move diagonally with them. Pressing Shift and a direction will move until you see/hit something.
Pressing > will take you down a staircase, and < to go up a staircase.
You can open doors by walking into them, and close them with C.
You can autoexplore by pressing o.
You can re-view recent messages with Ctrl-p.

Monsters and Combat

You can pick up items with , or g.
Wield weapons with w. Weapons have different stats.
- (You may also engage in Unarmed Combat, though it isn’t very effective when untrained).
Attack monsters in melee by walking in their direction (or with Ctrl-direction).
You can wait with . or s, passing your turn - such as to get monsters into a corridor with you.
You can rest with 5, waiting until you are fully healed, or something noteworthy happens.
Either mouseover and rightclick, or use x then v on the monster to examine monsters. Monsters with a red border are ‘dangerous’ relative to your current XP level (XL).
Quiver (often ranged) actions for further use with Q.
You can fire ranged weapons manually with f, or auto-target your quiver with p or Shift-Tab. Throwing weapons can be thrown immediately, while launchers (like bows) need to be wielded first.

Items and Inventory

View your inventory by pressing i. Most item related commands can also be done with this menu.
You can wear amour with W; amour gives AC, while heavier body armour reduces EV.
Autoexplore will automatically pick up useful items, such as potions and scrolls, if you aren’t in danger.
You can read scrolls with r and drink (“quaff”) potions with q.
Equipment items may have brands, with special properties. Branded equipment is blue when unidentified.
Equipment items may be artifacts, often with unique properties, and are unmodifiable. They are written in white.
You can evoke wands with V.
You can put on jewelry with P, and remove it with R.
Gold is used in shops, which can be interacted with by either > or <.

Magic and Spellcasting

Once you find a spellbook, you can memorize spells with M.
You need to be the same XL as the spell’s spell level in order to learn it, in addition to training magical skill (to lower failure rate).
Cast spells by pressing z, then the letter assigned to the spell. You may also Quiver a spell and then use it like a ranged weapon (with Shift-Tab).
You can view your memorized spells by pressing I (capital-i) or z.
Like HP, you can recover MP by resting (with 5).
Many spells can be positioned more effectively, or combined with other spells, in order to get (more effective) use out of them.
Heavier body amour and shields hamper spellcasting.

Gods and Divine Abilities

You may look at a god’s overview by praying at their altar (with > or <). After praying, you can worship the god by pressing Enter afterwards.
Gods all have unique features about them. Trog, the god of the tutorial, is also the god of rage and bloodshed, and so despises spellcasting.
Gods like and dislike different things. Most gods either like killing things (like Trog) or exploring new areas (like Elyvilon), rewarding you piety (divine favor) for doing so.
You should learn to use and even rely on divine abilities often, as they are usually very strong. Trog’s Berserk gives you 1.5x health, 1.5x speed (to all valid actions), and a big damage boost. Note that Berserk prevents most actions other than move and melee attack, and runs out very quickly if you aren’t attacking. And after berserk ends, you are slowed down and can’t berserk again for a short time.
In addition, the vast majority of abilities consume piety in the process. Regardless, this ability is very cheap, and the benefits are incredible, so don’t hold back!
Pressing ^ will let you view your current god, abilities, and piety.

Display xterm color palette

Thursday May 25, 2023 with tags ( linux )

bash xterm-palette.sh - will show you number of max colors available
bash xterm-palette.sh -v - will create a list of all colors with codes

#!/usr/bin/env bash
# xterm-palette.sh

trap 'tput sgr0' exit		# Clean up even if user hits ^C

function setfg () {
    printf '\e[38;5;%dm' $1
}

function setbg () {
    printf '\e[48;5;%dm' $1
}

function showcolors() {
    # Given an integer, display that many colors
    for ((i=0; i<$1; i++))
    do
	printf '%4d ' $i
	setbg $i
	tput el
	tput sgr0
	echo
    done
    tput sgr0 el
}

# First, test if terminal supports OSC 4 at all.
printf '\e]4;%d;?\a' 0
read -d $'\a' -s -t 0.1 </dev/tty
if [ -z "$REPLY" ]
then
    # OSC 4 not supported, so we'll fall back to terminfo
    max=$(tput colors)
else
    # OSC 4 is supported, so use it for a binary search
    min=0
    max=256
    while [[ $((min+1)) -lt $max ]]
    do
	i=$(( (min+max)/2 ))
	printf '\e]4;%d;?\a' $i
	read -d $'\a' -s -t 0.1 </dev/tty
	if [ -z "$REPLY" ]
	then
            max=$i
	else
	    min=$i
	fi
    done
fi


# If -v is given, show all the colors
case ${1-none} in
    none)
	echo $max
	;;
    -v)
	showcolors $max
	;;
    *)
	if [[ "$1" -gt 0 ]]; then
	    showcolors $1
	else
	    echo $max
	fi
	;;
esac | less --raw-control-chars --QUIT-AT-EOF --no-init

Sane defaults for tmux with more visible statusbar

Thursday May 25, 2023 with tags ( tmux )

# Remap prefix from 'C-b' to 'M-a'.
unbind C-b
set-option -g prefix M-a
bind-key M-a send-prefix

# Split panes using | and -.
bind | split-window -h
bind - split-window -v
unbind '"'
unbind %

# Start counting windows with 1.
set-option -g allow-rename on
set -g base-index 1
setw -g pane-base-index 1

# Statusbar: purple bg and white fg.
set -g status-bg '#480b8e'
set -g status-fg '#ffffff'

# Active window: black bg and white fg. 
set -g window-status-current-format "#[fg=#ffffff]#[bg=#111111]#[fg=#ffffff]#[bg=#111111] #I:#W #[fg=#ffffff]#[bg=#111111]"

# Disable mouse mode (tmux 2.1 and above).
set -g mouse off

My brand new Plan9/9front desktop

Wednesday May 24, 2023 with tags ( plan9 )

I have been experimenting with Plan9/9front for a week now. Noice! This is how my desktop looks like.

Extend Lua with custom C functions using Clang

Tuesday May 23, 2023 with tags ( lua c )

Here is a boilerplate for extending Lua with custom C functions. This requires Clang and Lua 5.1 to be installed. GCC can be used instead of Clang, but the Makefile will need to be modified.

nativefunc.c

#include <lua.h>
#include <lauxlib.h>

static int l_mult50(lua_State *L) {
  double number = luaL_checknumber(L, 1);
  lua_pushnumber(L, number * 50);
  return 1;
}

int luaopen_nativefunc(lua_State *L) {
  static const struct luaL_Reg nativeFuncLib[] = {{"mult50", l_mult50}, {NULL, NULL}};

  luaL_register(L, "nativelib", nativeFuncLib);
  return 1;
}

main.lua

require "nativefunc"
print(nativelib.mult50(50))

Makefile

CC       = clang
CFLAGS   =
INCLUDES = `pkg-config lua5.1 --cflags-only-I`

all:
  $(CC) -shared -o nativefunc.so -fPIC nativefunc.c $(CFLAGS) $(INCLUDES)

clean:
  rm *.so

Parse RSS feeds with Lua

Tuesday May 23, 2023 with tags ( lua rss )

Example of parsing RSS feeds with Lua. Before running the script install:

feedparser with luarocks install feedparser
luasocket with luarocks install luasocket

local http = require("socket.http")
local feedparser = require("feedparser")

local feed_url = "https://mitjafelicijan.com/feed.rss"

local response, status, _ = http.request(feed_url)
if status == 200 then
  local parsed = feedparser.parse(response)

  -- Print out feed details.
  print("> Title   ", parsed.feed.title)
  print("> Author  ", parsed.feed.author)
  print("> ID      ", parsed.feed.id)
  print("> Entries ", #parsed.entries)

  for _, item in ipairs(parsed.entries) do
    print("GUID    ", item.guid)
    print("Title   ", item.title)
    print("Link    ", item.link)
    print("Summary ", item.summary)
  end
else
  print("! Request failed. Status:", status)
end

Execute not blocking async shell command in C#

Monday May 22, 2023 with tags ( csharp )

Execute a shell command in async in C# while not blocking the UI thread.

private async Task executeCopyCommand()
{
  await Task.Run(() =>
  {
    var processStartInfo = new ProcessStartInfo("cmd", "/c dir")
    {
      RedirectStandardOutput = true,
      UseShellExecute = false,
      CreateNoWindow = true
    };

    var process = new Process
    {
      StartInfo = processStartInfo
    };

    process.Start();
    process.WaitForExit();
  });
}

Make sure that async is present in the function definition and await is used in the method that calls executeCopyCommand().

private async void button_Click(object sender, EventArgs e)
{
  await executeCopyCommand();
}

Change permissions of matching files recursively

Tuesday May 16, 2023 with tags ( linux )

Replace *.xml with your pattern. This will remove executable bit from all files matching the pattern. Change + to - to add executable bit.

find . -type f -name "*.xml" -exec chmod -x {} +

Previews how man page written in Troff will look like

Monday May 15, 2023 with tags ( troff )

Troff is used to write man pages and it is difficult to read it so this will preview how it will look like when it is rendered.

# On Linux system.
groff -man -Tascii filename

# On Plan9 system.
man 1 filename

Convert all MKV files into other formats

Sunday May 14, 2023 with tags ( ffmpeg )

You will need ffmpeg installed on your system. This will convert all MKV files into WebM format.

# Convert all MKV files into WebM format.
find ./ -name '*.mkv' -exec bash -c 'ffmpeg -i "$0" -vcodec libvpx -acodec libvorbis -cpu-used 5 -threads 8 "${0%%.mp4}.webm"' {} \;

# Convert all MKV files into MP4 format.
find ./ -name '*.mkv' -exec bash -c 'ffmpeg -i "$0" c:a copy -c:v copy -cpu-used 5 -threads 8 "${0%%.mp4}.mp4"' {} \;

Download list of YouTube files

Saturday May 13, 2023 with tags ( youtube )

If you need to download a list of YouTube videos and don’t want to download the actual YouTube list (which yt-dlp supports), you can use the following method.

// Used to get list of raw URL's from YouTube's video tab'.
// Copy them into videos.txt.
document.querySelectorAll('#contents a.ytd-thumbnail.style-scope.ytd-thumbnail').forEach(el => console.log(el.href))

Download and install https://github.com/yt-dlp/yt-dlp.

# This will download all videos in videos.txt.
yt-dlp --batch-file videos.txt -N `nproc` -f webm

Install Plan9port on Linux

Friday May 12, 2023 with tags ( plan9 )

Install Plan9port on Linux. This applies to Plan9port. This is a port of many Plan 9 programs to Unix-like operating systems. Useful for programs like 9term and rc.

sudo apt-get install gcc libx11-dev libxt-dev libxext-dev libfontconfig1-dev
git clone https://github.com/9fans/plan9port $HOME/plan9
cd $HOME/plan9/plan9port
./INSTALL -r $HOME/plan9

Fix bootloader not being written in Plan9

Thursday May 11, 2023 with tags ( plan9 )

If the bootloader is not being written to a disk when installing 9front on real harware try clearing first sector of the disk with the following command.

dd if=/dev/zero of=/dev/sdX bs=512 count=1

# If command above doesn't work try this one, wait couple of seconds and
# press delete key to stop the command.
cat </dev/zero >/dev/sd*/data

Take a screenshot in Plan9

Wednesday May 10, 2023 with tags ( plan9 )

Take a screenshot in Plan9. This applies to Plan9 and 9front. This will take a screenshot of the screen and output it to /dev/screen. You can then use topng to convert it to a png image.

# Instant screenshot.
cat /dev/screen | topng > screen.png

# Delayed screenshot (5 seconds).
sleep 5; cat /dev/screen | topng > screen.png

#cat-v on weechat configuration

Tuesday May 9, 2023 with tags ( irc )

Set up weechat to connect to #cat-v on oftc. This applies to weechat but should be similar for other irc clients.

# Install weechat and launch it and execute the following commands.

/server add oftc irc.oftc.net -tls
/set irc.server.oftc.autoconnect on
/set irc.server.oftc.autojoin "#cat-v"
/set irc.server.oftc.nicks "nick1,nick2,nick3"

Write ISO to USB Key

Monday May 8, 2023 with tags ( linux )

Write ISO to USB key. Nothing fancy here.

sudo dd if=iso_file.iso of=/dev/sdX bs=4M status=progress conv=fdatasync

Mount Plan9 over network

Sunday May 7, 2023 with tags ( plan9 )

First install libfuse with sudo apt install libfuse-dev.
Then clone https://github.com/ftrvxmtrx/9pfs and compile it with make.
Copy 9pfs to your path.

# On Plan9 side
ip/ipconfig # enables network
aux/listen1 -tv tcp!*!9999 /bin/exportfs -r tmp # export tmp folder

# On Linux side
9pfs 172.18.0.1 -p 9999 local_folder # mount
umount local_folder # unmount

Push to multiple origins at once in Git

Saturday May 6, 2023 with tags ( git )

Sometimes you want to push to multiple origins at once. This is useful if you have a mirror of your repository on another server. You can do this by adding multiple push urls to your git config. This is a shorthand for command above.

git config --global alias.pushall '!sh -c "git remote | xargs -L1 git push --all"'

Run 9front in Qemu

Friday May 5, 2023 with tags ( plan9 qemu )

Run 9front in Qemu. This applies to Plan9 and 9front.

Download from here http://9front.org/iso/.

# Create a qcow2 image.
qemu-img create -f qcow2 $HOME/VM/9front.qcow2.img 30G

# Run the VM.
qemu-system-x86_64 -cpu host -enable-kvm -m 1024 \
    -net nic,model=virtio,macaddr=52:54:00:00:EE:03 -net user \
    -device virtio-scsi-pci,id=scsi \
    -drive if=none,id=vd0,file=$HOME/VM/9front.qcow2.img \
    -device scsi-hd,drive=vd0 \
    -drive if=none,id=vd1,file=$HOME/VM/ISO/9front.386.iso \
    -device scsi-cd,drive=vd1,bootindex=0

Cache busting in Hugo

Monday May 1, 2023 with tags ( hugo )

{{ $cachebuster := delimit (shuffle (split (md5 "6fab11c6669976d759d2992eff1dd5be") "" )) "" }}

<link rel="stylesheet" href="/style.css?v={{ $cachebuster }}">

This 6fab11c6669976d759d2992eff1dd5be can be random string you generate use. You can use whatever you want.