Tech on Raveen Kumar

Resurrecting my website

Mon, 14 Sep 2026 00:00:00 +0000

I built this website with Hugo, and it was going well. Then I got sidetracked: publishing from Emacs Org mode, then Bear Blog. I wrote a lot on Bear Blog, but it had too many restrictions. Somewhere along the way, I lost the motivation.

I always wanted to resurrect my website, but I kept putting it off and let raveenkumar.xyz expire. Turn on auto-renew. Always. Otherwise someone else can buy your domain and put it up for sale.

Thank you, Bear Blog

Mon, 14 Sep 2026 00:00:00 +0000

On 31 August 2023, I wrote my first post on Bear Blog. The whole post: “Let’s start again shall we!”

I needed a fresh start. For two years, I had been building websites instead of writing on them. I wrote my own site, rewrote it, tried blogging platforms, learned to host it myself and paid a lot of money for VPSes. None of it got me writing.

Bear Blog did. Minimalistic yet functional, as I said back then. No plugins, no build step, nothing to maintain. Just a text box and a publish button.

I let Claude unfollow everyone on Instagram

Sat, 12 Sep 2026 00:00:00 +0000

Why

A year and a half ago I wrote Can’t/Won’t use Social Media anymore. I failed. I fell into the social media trap and wasted so much time on judgemental pricks. Now I’m leaving. Parially.

I will make my account public and post things I care about. Unfollow everyone. Except John Cena. He is right. No one can see me. I show what I want to.

Instagram gave me some good things and a lot more bad ones. It sucks you in and turns you into a different person.

Contacts Organizer cli app

Fri, 04 Sep 2026 00:00:00 +0000

macOS has a really good Contacts app, but managing it is a pain in the ass. So I took it upon myself to solve it with AI.

The goal was to find contacts that aren’t in any lists and organize them. I used Claude to build the app.

Initial prompt

I want to build a CLI application.

Is there a way to organize contacts in MacOS to lists from CLI terminal.

Generating Ghibli style art with ChatGPT is pretty neat

Tue, 01 Apr 2025 00:00:00 +0000

How to learn programming

Wed, 19 Mar 2025 00:00:00 +0000

F*ck around until it works

Messing around is the only way to learn programming

My favorite programming language and tools

Wed, 19 Mar 2025 00:00:00 +0000

Programming is always fun. At least for me. When I program for myself with lots of freedom, I have lots of fun. But at work not so much. There is quite a lot of restrictions and it kills me to say that I absolutely hate corporate programming.

That being said, I do enjoy some programming languages and tools that I use regularly.

Programming Languages for fun

Bash
Python
VimScript
Emacs Lisp

Programming languages I use for work

System Verilog and Verilog
UVM

Tools

Vim / Emacs
ChatGPT

Hardware

MacBook Air m1
Mac mini M2 Pro with triple monitor setup

Vim not retaining file and command history

Fri, 19 May 2023 00:00:00 +0000

This solved the problem.

https://unix.stackexchange.com/questions/43033/what-would-cause-vim-not-to-retain-command-history

Check presence and rights for ~/.viminfo. Usually that’s it which keeps command history, file editing positions, etc. One possible case is that this file belongs to root.

Unsubscribe from Emacs Org-mode mailing list

Wed, 17 May 2023 00:00:00 +0000

Visit this link and follow the instructions - https://lists.gnu.org/mailman/options/emacs-orgmode

https://emacs-orgmode.gnu.narkive.com/SrK9BVd1/o-how-i-can-unsubscribe-this-mail-list

fc fix command or fix previous command

Fri, 12 May 2023 00:00:00 +0000

In Bash, fc stands for “fix command” and it is a built-in command that allows you to work with the command history. The fc command provides a way to view, edit, and re-execute commands from your command history.

Here are some common uses of the fc command:

Viewing command history: You can use fc -l or simply fc to display the list of recently executed commands. By default, it shows the most recent commands with line numbers.

Insert a string at the beginning of all cells in a column

Wed, 10 May 2023 00:00:00 +0000

Insert a new column before it. Type this formula in the first cell and autofill the remaining,

= "New String" & A1

Copy all the required cells in the column and paste it to the original location as values.

Delete the newly inserted row.

Grep for files that does not contain a specific string

Tue, 09 May 2023 00:00:00 +0000

Another useful way to use grep is for printing file names that do not contain a specific string, for example

grep -L "string" *

You can use the -L option of the grep command, which prints the names of all files that do not contain the specified search string.

The * at the end tells grep to search all files in the current directory. If you want to search only specific files or directories, you can replace the * with the filenames or directory names.

Periodically run a program and watch the output

Fri, 05 May 2023 00:00:00 +0000

watch

Execute a program periodically, showing output fullscreen

Example

watch ls

alternative - viddy

Horizontally print file contents

Wed, 03 May 2023 00:00:00 +0000

To concatenate the contents of a vertical file horizontally in Unix, you can use the paste command with the -s option.

Here’s an example:

Let’s say you have a file file.txt with the following vertical content:

apple
banana
orange

You can concatenate the contents horizontally using the following command:

paste -s file.txt

This will produce the output:

apple   banana  orange

The -s option tells paste to concatenate the lines horizontally instead of vertically. By default, paste separates the columns with a tab character. If you want to use a different separator, you can specify it with the -d option followed by the separator character. For example:

Power of 2s

Thu, 20 Apr 2023 00:00:00 +0000

n	2^n
0	1
1	2
2	4
3	8
4	16
5	32
6	64
7	128
8	256
9	512
10	1,024
11	2,048
12	4,096
13	8,192
14	16,384
15	32,768
16	65,536
17	131,072
18	262,144
19	524,288
20	1,048,576

Reading notes - Designing a Video Game hardware in Verilog

Thu, 20 Apr 2023 00:00:00 +0000

Book: Designing Video Game Hardware in Verilog, Steven Hugg (2018).

2023-04-20-power-of-2s

Byte - 8 bits Nibble - 4 bits

/*
A clock divider in Verilog, using the cascading
flip-flop method.
*/

module clock_divider(
  input clk,
  input reset,
  output reg clk_div2,
  output reg clk_div4,
  output reg clk_div8,
  output reg clk_div16
);

  // simple ripple clock divider
  
  always @(posedge clk)
    clk_div2 <= reset ? 0 : ~clk_div2;

  always @(posedge clk_div2)
    clk_div4 <= ~clk_div4;

  always @(posedge clk_div4)
    clk_div8 <= ~clk_div8;

  always @(posedge clk_div8)
    clk_div16 <= ~clk_div16;

endmodule

Static timing anaysis

Setup time and hold time are timing constraints that must be met in digital circuits to ensure correct data transfer between logic elements. These constraints are important to consider in the design of synchronous digital circuits, which use a clock signal to synchronize the transfer of data between flip-flops or other storage elements.

Emacs symbol search at point

Wed, 12 Apr 2023 00:00:00 +0000

To enter symbol search press M-s . this with execute isearch-forward-symbol-at-point function. This is similar to vim’s * key. I accitentally pressed it instead of M-s h . and found it while trying to highlight a symbol, lol.

Mark ring and Jumplist with emacs and helm

Fri, 07 Apr 2023 00:00:00 +0000

Like vim, emacs has an alternative to jump list. It is called mark rings but its difficult to use. Fortunately there is a helm and counsel function to help us navigate the mark rings. Add this following command to emacs init file,

(global-set-key (kbd "C-c '") 'helm-all-mark-rings)

I use C-c ' to browse mark rings.

Stop asking tags table to be reset every time a new file is visited in a different project

Fri, 07 Apr 2023 00:00:00 +0000

(setq tags-add-tables nil)

Emacs configuration for perl programming

Fri, 03 Mar 2023 00:00:00 +0000

Configuration taken from https://www.emacswiki.org/emacs/CPerlMode

;;; Perl
;; cperl-mode is preferred to perl-mode
;; "Brevity is the soul of wit" <foo at acm.org>
(defalias 'perl-mode 'cperl-mode)
(setq cperl-invalid-face nil) 
(setq cperl-electric-keywords t) ;; expands for keywords such as foreach, while, etc...
(setq cperl-hairy t) ;; Turns on most of the CPerlMode options

Python docstrings

Tue, 28 Feb 2023 00:00:00 +0000

In python, docstrings are used to define the functions documentation. Refer this page,

https://peps.python.org/pep-0257/


def function(a, b):
    """Do X and return a list."""

Git hangs on git pull or git fetch

Mon, 27 Feb 2023 00:00:00 +0000

Sometime I find git hanging in wsl and it is not able to recover. The only way to recover is restarting the computer.

How-to delete an element from a xml tree in Python

Mon, 27 Feb 2023 00:00:00 +0000

Following are the steps to delete an element from a xml tree proprly when parsing with python,

https://stackoverflow.com/questions/47041688/remove-element-from-xml-with-elementtree

Example XML tree


<foo>
   <bar>
      <level>
         <test name="1">
            <stuff>
               hello
            </stuff>
         </test>
         <test name="2">
            <stuff>
               hello
            </stuff>
         </test>
      </level>   
   </bar>
</foo>

Python code to delete stuff


import xml.etree.ElementTree as ET

tree = ET.parse('myfile.xml')
root = tree.getroot()

for test in root.iter('test'):
    for stuff in test.findall('stuff'):
       test.remove(stuff)

print ET.tostring(root)

You need to have pointer to parent tag in order to remove child tag.

Fuzzy matching with python

Sun, 26 Feb 2023 00:00:00 +0000

Fuzzy matching is great. In fact, it is better than regular expression matching in certain cases. Come to think of it, our entire human brain works on fuzzy matching.

Take handwriting, for example, everyone can read each other’s handwriting as long as it’s legible. That’s fuzzy matching on an organic level.

I had a problem where I have a string of text, and I wanted to match the substring with other string but the issue is that the substring varies from string to string and I cant predict the proper substring to do a regex matching. So suddenly out of the blue I got an idea to do a fuzzy matching.

rsync is weird, does not sync "tags" directory

Fri, 24 Feb 2023 00:00:00 +0000

For whatever reason rsync decided not to sync tags directory since it is ignored in CVS mode. Took a lot time to figure out the problem. Finally this command works correctly.

--include used to sync everything, despite ofthe cvs option, -C. But removed in this command.

	rsync -av --delete --checksum --copy-links -rPuzhi ./public/ root@raveenkumar.xyz:/var/www/raveenkumar/

Ask bing

Thu, 23 Feb 2023 00:00:00 +0000

Today I got access to bing chat feature. Finally AI search is here, lets see how well this goes. Based on my chat it seems much dumber than chatgpt.

Emacs keybindings work on macos

Thu, 23 Feb 2023 00:00:00 +0000

I was suprised to find out that when I accidentally pressed ctrl-k on a line it killed it in macos. Looks like some emacs keybindings are supported system wide by default.

http://irreal.org/blog/?p=259

Explained in this blog post.

【Ctrl+f】, 【Ctrl+b】, 【Ctrl+a】, 【Ctrl+e】, 【Ctrl+k】, 【Ctrl+y】, 【Ctrl+p】, 【Ctrl+n】, and a few others work across the whole system.

Adding epiog to python scripts using argparse module

Mon, 20 Feb 2023 00:00:00 +0000

https://docs.python.org/dev/library/argparse.html#argparse.RawDescriptionHelpFormatter

We can add epilog to argparse help and description to add more info. Refer link above.

Emacs File-info package

Mon, 20 Feb 2023 00:00:00 +0000

Found a new package today. Does exactly what I want. List and copy the file info and path with a keybind and a popup window.

https://github.com/Artawower/file-info.el

Installation:

Add this to you init.el file

;; File-info
(use-package hydra
  :straight t)
(use-package browse-at-remote
  :straight t)
(use-package posframe
  :straight t)
(use-package file-info
  :straight (:host github :repo "artawower/file-info.el")
  :bind (("C-c f i" . 'file-info-show))
  :config
  (setq hydra-hint-display-type 'posframe)
  (setq hydra-posframe-show-params `(:poshandler posframe-poshandler-frame-center
                                               :internal-border-width 2
                                               :internal-border-color "#61AFEF"
                                               :left-fringe 16
                                               :right-fringe 16)))

Emacs wrap region package

Mon, 20 Feb 2023 00:00:00 +0000

https://github.com/rejeep/wrap-region.el

Wrap Region is a minor mode for Emacs that wraps a region with punctuations. For “tagged” markup modes, such as HTML and XML, it wraps with tags.

How to copy paste as plain text into gmail on ios

Mon, 20 Feb 2023 00:00:00 +0000

https://apple.stackexchange.com/questions/354992/how-to-copy-and-paste-as-plain-text-on-ios

Paste formatted
Select the just pasted text and in the context menu swipe right and tap on “Share…”
In the Share sheet, tap on “Copy”. This copies as plain text!
Tap still selected text to get the context menu again
In the context menu tap on “Paste” to replace the selected, formatted text with its plain text representation

PHP Notes

Mon, 20 Feb 2023 00:00:00 +0000

PHP Notes

Recursively grep with emacs lisp only

Mon, 20 Feb 2023 00:00:00 +0000

I was looking for a way to recursively grep inside a directory and a find-grep replacement since its not availabe in windows and I found this.

https://www.reddit.com/r/emacs/comments/bxtwfg/grep_and_find_but_in_pure_emacs_lisp/

(project-find-regexp)

My webside ideas

Sun, 19 Feb 2023 00:00:00 +0000

Tags are better than folders
Write things chronological and as essays and tag some keywords
Let it sort itself on the fly based on tags
Use less folders
Less structure more flow

AWK

Sat, 18 Feb 2023 00:00:00 +0000

Example 1

awk -F ',' '{print $NF}' {{filename}}

To print only rows with columns matching a specific string

awk '$3 == "hello"' file

This will match with, 1 2 hello something but not with, 1 2 world something

Example 2: Awking and cutting some stuff

Lets assume that you want to print the 1st and 3rd field in one line.

echo "A:B:C:D:E:F:G" | awk -F ':' 'ORS=" " {print $1} {print $3}'

Here ORS stands for, The output record separator, by default its a newline.

Cat

Sat, 18 Feb 2023 00:00:00 +0000

Join multimedia files

cat movie.mpeg.0* > movie.mpeg
cat *mp3 > combined.mp3

Coding Guidelines

Sat, 18 Feb 2023 00:00:00 +0000

First rule of coding, do not code
Second rule of coding, write less code whenever you can

cp

Sat, 18 Feb 2023 00:00:00 +0000

Dereference / follow and copy symbolic links

cp -L source dest

COPY ONLY FILE THAT DO NOT EXIST IN THE DESTINATION DIRECTORY - UPDATE

cp -u *.html destination

Cut

Sat, 18 Feb 2023 00:00:00 +0000

Cut from 25th column

https://superuser.com/questions/316785/is-there-a-diff-utility-that-allows-you-to-exclude-columns

cut -c25- file.txt

Cut fields

echo "1:2:3" | cut -d ":" -f 1

1

du

Sat, 18 Feb 2023 00:00:00 +0000

Find size of all files and directories under current directory and sort it based on size

du -sh * | sort -h

FFMPEG notes

Sat, 18 Feb 2023 00:00:00 +0000

Basic usage

ffmpeg -i input.mp4 output.mp4

Scale video to height 1080p

ffmpeg -i input.mp4 -vf "scale=-2:1080" output.mp4

Remove audio track from a video file

ffmpeg -i input.mp4 -an output.mp4

Slow down a video

https://trac.ffmpeg.org/wiki/How%20to%20speed%20up%20/%20slow%20down%20a%20video

ffmpeg -i "$infile" -filter:v "setpts=2.0*PTS" "slowmo-$infile"

Interpolate videos to high fps

ffmpeg -i input.mkv -filter:v "minterpolate='mi_mode=mci:mc_mode=aobmc:vsbmc=1:fps=120" output.mkv

Concat video files

# mylist.txt file format
# this is a comment
file '/path/to/file1.mp4'
file '/path/to/file2.mp4'
file '/path/to/file3.mp4'

ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4

Cut video files

Following example cuts a video from 5 seconds to 10 seconds and exports it. Alternatively, use this software

Locate

Sat, 18 Feb 2023 00:00:00 +0000

Description

Locate is a alternative to find for files. Locate uses updatedb command to update its database. Note that we must run the updatedb command everytime there is file system change.

Example

Create a database

updatedb

Locate files

locate filename

Create a database locally

updatedb_path="$HOME/.local/locate_db"
updatedb_home="$updatedb_path/home.db"
updatedb -l 0 -o "$updatedb_home" -U ~/

Locate files for locally created database

locate -d "$updatedb_home"

pandoc

Sat, 18 Feb 2023 00:00:00 +0000

https://pandoc.org/MANUAL.html

pandoc -o output.html input.txt

Powershell notes

Sat, 18 Feb 2023 00:00:00 +0000

Winget

To install any program using powershell in similar way to linux use, winget

Example:

winget install pandoc

Sed

Sat, 18 Feb 2023 00:00:00 +0000

To replace text

sed 's/text/replacement_text/g' <file_name>

To replace text and write file

sed -i 's/text/replacement_text/g' <file_name> ** Append to beginning of a file sed -i ‘1i text’ file.txt * back

Find and replace a specific line from all files in current directory matching a specific extension

Here, all .md files have

<a id="org55550fd"></a>

Line in it. The following command deletes those lines from all the files.

find . -iname "*.md" -exec sed -i '/<a id=*/d' {} \;

TMUX

Sat, 18 Feb 2023 00:00:00 +0000

The greatest samurai to ever exist?

TMUX plugins

GitHub - tmux-plugins/tpm: Tmux Plugin Manager

GitHub - tmux-plugins/tmux-urlview: Quickly open any url on your terminal window!

GitHub - tmux-plugins/tmux-resurrect: Persists tmux environment across system restarts.

To move a pane from another window to current window

join-pane -s target-window:target-pane

To use 256 colours in Tmux

256 colours in TMUX

You should set the default terminal in .tmux.conf to be screen-256color,

set -g default-terminal "screen-256color"

Windows WSL Notes

Sat, 18 Feb 2023 00:00:00 +0000

https://thomasward.com/wsl2-x11/

Change password

To change to root user

ubuntu config --default-user root

To change password

passwd, passwd <user_name>

Open Windows GUI applications with Linux command line

mspaint.exe file.png
notepad.exe file.txt

https://dev.to/adityakanekar/upgrading-from-wsl1-to-wsl2-1fl9

bc

Fri, 17 Feb 2023 00:00:00 +0000

bc as a hex calculator

obase=16
ibase=16
9+1

bc fractional

scale=10
1/3

Evaluating expressions from commandline

bc <<< "ibase=10; obase=16; $(grep cru_spare -r | awk -F "," '{print $NF}')"

C++ notes

Fri, 17 Feb 2023 00:00:00 +0000

For loops

for (uint32_t i=0; i<10; i++) {
printf("i = %d", i);
}

Prints

printf(“unsigned = %u”, var1); printf(“signed = %d”, var1);

Functions

https://softwareengineering.stackexchange.com/questions/286490/what-is-the-difference-between-function-and-functionvoid 6.7.6.3 Function declarators (including prototypes) 10 The special case of an unnamed parameter of type void as the only item in the list specifies that the function has no parameters. 14 An identifier list declares only the identifiers of the parameters of the function. An empty list in a function declarator that is part of a definition of that function specifies that the function has no parameters. The empty list in a function declarator that is not part of a definition of that function specifies that no information about the number or types of the parameters is supplied.145)

Copy and paste as plain text into gmail on ios

Fri, 17 Feb 2023 00:00:00 +0000

When you copy text anywhere in the browser from an ios device, it is a formatted text. To paste is as a plain text do the following.

Paste formatted
Select the just pasted text and in the context menu swipe right and tap on “Share…”
In the Share sheet, tap on “Copy”. This copies as plain text!
Tap still selected text to get the context menu again
In the context menu tap on “Paste” to replace the selected, formatted text with its plain text representation

Reference: