Srivathsan Murali

Strip those ANSI symbols

Thu, 27 Mar 2025 00:00:00 +0000

I have several pet peeves. One I consider to be a programming sin.

Lets imagine, you are asked to integrate a library into your system. You plug it in, call the required API and you run your test executable to see if it works. Well, you see a wall of white. WHITE….

Of course, the library assumes that the terminal has a dark background and sets foreground colour of its stdout to WHITE. WHYYYYYYYY Well, sinners aside, how do we handle this on our end besides fixing the damn loggers.

Simple enough, strip the ANSI colour codes from the executable by piping the output through a ANSI stripper.

Here are a few ways of doing so.

Option 1:

ansi2txt from colorized-log. Its a small enough c program that does a single thing.

This is my preferred option. I just stole the c file and dumped a binary into my dotfiles.

Option 2:

Ansifilter, seems a bit too powerful for this usecase. But also does the job.

Option 3:

Pipe through tee, it generally does a good job at stripping ansi sequences

Option 4:

SED IS THERE SOMETHING THIS DOES NOT DO. <3

STUPID_CMD | sed -r "s/[[:cntrl:]]\[[0-9]{1,3}m//g"

Option 5:

TR. My dear translate. This solves the issue by replacing all characters that are not either printable or whitespace This is another elagent solution, if I didn’t have the custom ansi2txt program, this would probably be the way I would go.

STUPID_CMD | tr -dc '[[:print:][:space:]]'

Options 6: Novel solution for macos

This seems a bit convoluted, but you could use the clipboard to do it for you.

STUPID_CMD | pbcopy && pbpaste

Topographic Map of Singapore

Wed, 28 Jul 2021 00:00:00 +0000

I recently purchased the Ender 3 V2 3D printer to print miniature for D&D and it has been great for that. I love being able to print any monster mini I need for a game. I have also been trying to do other prints with the printer, simple utility items. I had an idea to make a 3D topography map and as I am currently living in Singapore I decided to make one of this fine city.

Turns out Singapore is quite flat, I should have seen this coming. With the highest point being around 136 metres, its not the best representation of this process but I wanted to document how I managed to do it.

Here is the end result.

The process is quite simple:

Get the coordinates for the location you want to generate the topographic map for.
Use the Terrain2STL web app to produce the topographical map as a stl file.
- In my case, I scaled the Z axis by 4 to be able to see something three dimensional.
Pop the stl file into your slicer of choice (I used cura) and generate the gcode for your printer and print away.
I did manage to paint the map afterwards just to get more from it but it looked really with just a coat of primer.

Vdirsyncer and Khard

Sun, 12 Jul 2020 00:00:00 +0000

In the last post, I discussed about how to setup calendar sync using vdirsyncer and how to manage the calendar in the terminal using khal. In this I will discuss how to sync your contacts using vdirsyncer and how to manage them using khard.

As I used Vdirsyncer to sync calendars using CalDAV, in this post, I will use it sync contacts over CardDAV. As before I will show installation commands for Arch Linux.

Setup Vdirsyncer

In the previous post, I explained how to setup sync your calendar with CalDAV, in this section, I will do that same for contacts. CalDAV and CardDAV are very similar services that are based on WebDAV. To setup the contacts sync, add the following section to the vdirsyncer configuration.

[pair default_contacts]
a = "defatul_contacts_local"
b = "defatul_contacts_remote"
collections = ["from a", "from b"]
conflict_resolution = "a wins"

[storage default_contacts_local]
type = "filesystem"
path = "~/.local/share/vdirsyncer/carddav"
fileext = ".vcf"

[storage default_contacts_remote]
type = "carddav"
url = "https://contacts.example.com/carddav"
username = "user@example.com"
password.fetch = ["command", "pass", "show", "email/user@example.com"]

Similar to the calendar setup, the setup for local and remote are separated. Where the local storage is filesystem folder and the remote storage is a CardDAV server that you have access.

Once the config is setup, make vdirsyncer setup the contacts folder structure and test the remote connection.

vdirsyncer discover default_contacts

Once the setup is done, you can sync your contacts using the following command.

Vdirsyncer sync default_contacts

I use cron to regularly sync the local and remote contacts.

Install and setup Khard

Now the vCard files are synced using vdirsyncer, Khard can be used to manage your address book. Khard is a CLI application that is super simple to use and can be easily integrated into a terminal mail client (I will discuss about my email setup soon).

You can install Khard using the following command.

sudo pacman -S khard

Khard needs to be configured to use the synced address book. This is the configuration I use to access my contact list. It is very much based on the example config file in the Khard repo.

# ~/.config/khard/khard.conf

[addressbooks]
[[contacts]]
path = ~/.local/share/vdirsyncer/carddav/contacts/

[general]
debug = no
default_action = list
# These are either strings or comma seperated lists
editor = nvim, -i, NONE
merge_editor = vimdiff

[contact table]
display = first_name
group_by_addressbook = no
reverse = no
show_nicknames = no
show_uids = yes
sort = last_name
localize_dates = yes
preferred_phone_number_type = pref, cell, home
preferred_email_address_type = pref, work, home

[vcard]
private_objects = Twitter, Mastodon
preferred_version = 3.0
search_in_source_files = no
skip_unparsable = no

This configuration file is pretty much the same as the example config in the repo. I have just modified it to point to the correct address book directory and change the editor I use. Everything else remains as default.

With this now configured, I can now access my contacts with the khal list command or other commands available to the user.

Vdirsyncer and Khal

Thu, 09 Jul 2020 00:00:00 +0000

Calendar is a very important tool that most people use regularly to manage their time. I end up setting events for most things. Setting up a easy to use calendar that is synced across all my devices is important. I use Zoho Mail to host my email which also provides me with Calendar support. I will describe my calendar setup on my computers.

I use vdirsyncer to synchronize caldav with local copy of the events and use Khal to read and write them.

All installation commands are shown for Arch Linux, but you should be able to find packages for most Linux distributions.

Install and setup Vdirsyncer

Vdir is a standard format to store calendar as a .ics file in the filesystem. We can use vdirsyncer to events to your CalDAV endpoint.

First install vdirsyncer using the following command.

sudo pacman -Ss calcurse

Once vdirsyncer is installed, you can setup CalDAV synchronization using the following config at ‘$HOME/.config/vdirsyncer/config’

# $HOME/.config/vdirsyncer/config
[general]
status_path = "~/.local/share/vdirsyncer/status/"

[pair default_calendar]
a = "default_calendar_local"
b = "default_calendar_remote"
collections = ["from a", "from b"]
metadata = ["color"]

[storage default_calendar_local]
type="filesystem"
path="~/.local/share/vdirsyncer/calendars/"
fileext = ".ics"

[storage default_calendar_remote]
type="caldav"
url="https://calendar.example.com/caldav/"
username="user@example.com"
password.fetch = ["command", "pass", "show", "user@example.com"]
# password = "Password1234" # If you would like to store password directly.

The config is quite simple, you setup the local and remote location to store calendar. The only information you need is the CalDAV endpoint for your calendar.

Once the config is setup, make vdirsyncer setup the calendar folder structure and test the remote connection.

vdirsyncer discover default_calendar

Once the setup is done, you can sync your calendar using the following command.

Vdirsyncer sync default_calendar

I use cron to regularly sync the local and remote calendars.

Install and setup Khal

Khal is a CLI calendar program. It allows you to read and write to a vdir folder. With vdirsyncer syncing the CalDAV, I use khal to manage my calendar from my terminal. It also enables me to add events from my terminal email client, aerc.

You can install Khal using the following command

sudo pacman -S khal

Once you have installed khal, we can point khal to use the calendar we sync with vdirsyncer. This is a example configuration of the khal config file.

# $HOME/.config/khal/config
[calendars]
[[default]]
path = ~/.local/share/vdirsyncer/calendars/events/
type = calendar
color = dark green

[locale]
timeformat = %I:%M %p
dateformat = %d/%m/%Y
longdateformat = %d/%m/%Y
datetimeformat = %d/%m/%Y %I:%M %p
longdatetimeformat = %d/%m/%Y %I:%M %p

Once the setup is completed, you can access the list of events using either khal list or khal calendar. To create an event, you can use khal new.

If you have an ics calendar file, you can use khal import <ics file>. Or if you need to interactively browse through the calendar, you can use ikhal.

Curse of Strahd

Mon, 06 Jul 2020 00:00:00 +0000

Strahd Von Zarovich, is one of the best written villain in the D&D mutliverse. His backstory thrusts the party into a wonderful story about an endless life and power; and what that how that transforms Strahd and his conquered land into realm into eternal darkness and death.

Curse of Strahd, brings the brilliant story of the dark lord as a excellent Gothic horror, where the characters are always looking behind their backs. If you would like to learn more about the actual adventure, I recommend buying the book. The book is very well written and I will not do it justice.

I am going to be talking about the changes I made to the game as I ran it and where I stole some ideas for the game from. I will also talk about some of the challenges I faced as the DM for this campaign.

——– Spoilers Ahead ——–

Scale. There is a significant problem I have with the scale of the map of Barovia. As written, the you can travel from one end of the map to the other end in about 4-5 hours, if you are get lucky that is. If you are unlucky, you could be killed by werewolves, hags, druids, Strahd randomly walking around and a very mean lady in a hut if you get lost. It is ridiculous that a level 3 party might go out of the first village and get caught by a hag coven after walking for 2 hours. I personally scaled up the map so that it takes four days to travel across the map. This also has the added benefit of making sure, the party camps out at night. Because in my opinion the best parts of the campaign are the intrigue in the cities and everything else in the forests. The more time, they spend travelling, the more time to build up horror.

Card Reading as Adventure Hook. Using the card reading as an adventure hook is introduced by DragnaCarta, as a plot hook to get the characters invested in saving Barovia. With this at the start of the campaign, every character gets a vision from Madam Eva in which she tells to seek her out and get a card reading. They then wake up with a card that they bring to her in the adventure. This also helps in dropping bread crumbs to various adventures in Barovia. It helps the DM to connect the player character’s back stories to the story of Barovia.

Tome of Strahd. The Tome of Strahd, is a great story device that lets the party learn about the Strahd’s story. But I think, giving the players a big info dump when you get the book doesn’t feel like a lot of fun. In order to make understanding Strahd’s story in more bite sized manner, I made the book itself enchanted to protect whats written. This makes it an ongoing skill challenge to decrypt whats written. Of course, this is not an original idea, many have done this before. I stole the idea from this post on reddit. I did modify it but the post explains the gist of it.

The Tome as provided in the adventure module is very small for an actual journal. I used the extended tome which includes more information from the ‘I, Strahd’ novel.

Fanes. Strahd defeated the three archfey ladies to gain control of the land. This is done by desecrating the three fanes corresponding to each lady of the land. I was able to intertwine the adventure of slowly reconsecrating the fanes and draining Strahd’s power over the land with the back story of a character. This also lets the players be more invested in the rest of Barovia instead of just doing the adventures to level up to fight Strahd. I gathered this idea from MandyMod’s Fanes of Barovia post.

Lancelot. For an extra bit of drama, I gave the party a puppy. First, it gives the party some kind of familiarity in this dark realm. At the same time adds an extra being to worry about. My party carried the puppy all the way to the end of the campaign slowly trailing it all the way. This could also be a good way to nudge the party find Gertrude if you make the puppy hers.

Important Resources

Curse of Strahd is a beautifully written adventure that has potential to tell an extraordinary story along with your group. I hope this has been useful :D

“I am the Ancient… I am the Land” ─ Strahd Von Zarovich

Writing my next campaign

Fri, 03 Jul 2020 00:00:00 +0000

I have been playing D&D for the last three years and I absolutely love it. Like most people who start with D&D 5e, I played Dwarf Cleric in a “Lost mines of Phandelver” campaign. This led me to run three campaigns with two different groups of people over the last two years. And I have never felt joy in a hobby before. This post is going to walk through my current process to how I plan my campaigns and how I would like to improve.

The first campaign I ran was Curse of Strahd , one of the finest adventures that were written. Being the first long term campaign I ran, I went for a pre-written campaign. The adventure was augmented with modifications that I homebrewed or ones I stole from the subreddit for it. I will write a post on this adventure in the future.

I ran the same homebrew campaigns that I wrote for two different groups and they couldn’t have gone in two different ways. This time I decided to write a campaign because I saw a how elemental energy was used in the Wu Assassins TV show. The show was quite bad but this gave me the idea of elemental nodes being spit out in the world and what would happen if one person had control over all four elemental powers.

So my current process to write a campaign is to build only upto 3 sessions forward. When I started with my homebrew campaign, I didn’t have any idea beside the fact that I wanted to have a node thrust into the world for each element. Beyond which, I didn’t have much and I went along this path.

Draw map for my world, .
Write the first session adventure and build up the village where it would happen.
And then write session by session.

This worked for the first part of campaign, as I could keep up with the party considering the nodes as the point of focus. As the party become more powerful and started gathering these nodes, I had to quickly scramble for a final villain and why they are gathering the nodes.

This become more of a problem as I ran the campaign for two groups at the same time. Of course, they didn’t approach the game in the same manner. Different cities, continents and different reactions to NPCs.

As the two campaign as coming to a close, I think, there is significant lack of sense of dread that I enjoyed in the Curse of Strahd campaign. The parties also were not as into the main villain as there were not as many breadcrumbs I left in the start of the campaign.

Things I learnt from running Curse of Strahd and my homebrew campaign.

Decide what you want the endgame to be about. Its easier to lay breadcrumbs.
Build your map or steal one. But having a general overview is useful. I also like drawing maps. So yay.
Have a common concept/idea for the enemies that is related to the endgame.
Figure out how to build the Player Character backstories into the world.
Write basic information about important factions and organizations.
Writing each city as you go is fine. Fill in NPCs from factions as you go.
Maybe not run two groups if possible at least not the same campaign.

I have learnt a lot by running these campaign. I have come to enjoy D&D very much and can’t wait to run another one. For the next one, I am thinking about a wild west style campaign with very little magic.

Common Website Practices

Sat, 27 Jun 2020 00:00:00 +0000

I have failed to build a ongoing blog many times. But always had followed many of them. I want to collect some common practices that I see in blogging practices and give my thoughts on. Just as a note to myself when I eventually decide to rebuild this blog once again. FYI, this will be evolving list.

1) HTTPS is a must.
Totally agree with this one. With Let’s Encrypt being an awesome non-profit Certificate authority, there is no reason, one should not have ssl certificates setup. Its 2020, this is the least expected.

2) RSS is still pretty good.
RSS is great and all blogs should have one. I tend not to follow blogs which don’t have rss feeds. Its just simpler.

Also add RSS auto discovery to all pages on your site.

3) Dynamic websites are an overkill.
Dynamic websites do make things easier but for a blog that is maintained by one single person, it is overkill. Static sites load faster and you don’t need any dynamic content.

4) Keep the website minimal.
People go to blog to read and it is always good to make the website simple to navigate and fast to load. No need for fancy JS or any moving parts.

Linux 101 - firewall

Mon, 06 Jan 2020 00:00:00 +0000

Firewall is a utility that is used to filter packet traffic in a network. It is used to whitelist traffic certain ports. Moreover, the protool used can also filtered.

Whitelisting is the process of denying all traffic except a choice few. This can be used to secure your server by restricting access to ports and services you don’t want to be public.

You could allow certian ports to be available only from certain IP’s. In this way, you can allow a trusted network to have access to your services while denying access from other IPs.

Iptables is the command line utility used to manage the linux’s kernel level firewall. Though, the kernel firewall can be configured using iptables command. It is often configured using a frontend.

Uncomplicated Firewall (ufw)

Ufw or the aptly named Uncomplicated Firewall is an easy to use fronted to iptables.

Install

This is the default firewall in ubuntu and debian and it should be installed by default.

If you do use other linux distributions, it should be easy enough to find the required package to install. In archlinux, it can be installed by running the following command.

sudo pacman -S ufw

Once installed, the utility is inactive by default and needs to be enabled to use. But be careful, if you are setting up the service on a server via SSH, you must allow ssh before enabling Ufw otherwise you might find yourself locked out of your machine.

Enable and Disable

The utility is enabled in two steps, you need to make sure that the ufw.service unit is enabled started in systemd. You can use the following command to do that.

sudo systemctl enable --now ufw.service

the --now flag also starts the service after enabling it.

Now that the ufw daemon is up and running, it is time to enable the firewall by using

sudo ufw enable

You can check the ufw status using the sudo ufw status command.

To disable the firewall simply run the sudo ufw disable

Configuring your firewall

sudo ufw status will show you the list of rules that are active. This can be changed using the following commands.

command	description
`sudo ufw allow RULE`	Allow traffic that matches given rule
`sudo ufw deny RULE`	Deny traffic that matches given rule
`sudo ufw reject RULE`	rejects traffic that matches given rule
`sudo ufw limit RULE`	deny if more than 5 requests in the last 30 seconds
`sudo ufw delete RULE`	delete a given rule

Rule Syntax

The rules can be specified as a string that includes the port number and optionally the protocol.

For example the rule for SSH can is 22/tcp, where 22 is the port used by ssh servers by default and tcp is the protocol that is used. If a protocol is not specified, both tcp and udp protocols would satisfy the rule.

So if you would like to enable ssh access to the machine, you can run the following command:

sudo ufw allow 22/tcp

In case of services like ssh, you can also use the service name to use the list of known services by ufw. This list can be found in /etc/services.

sudo ufw allow ssh
# equivalent to
# sudo ufw allow 22/tcp

sudo ufw allow http
# sudo ufw allow 80/tcp
sudo ufw allow https
# sudo ufw allow 443/tcp

This list only specifies the default ports. If you use different ports, please set the rules by yourself.

The full syntax can be used to specify a bit more information and more intricate rules.

For example, to allow ssh in the full syntax, you use the following command:

sudo ufw allow proto tcp to any port 22

The rules can also be specified using a full syntax. It lets you configure the firewall in more intricate manner. But most cases the simple syntax explained here should suffice. If you would like learn more about the other capabilities of or the full syntax a simple command will help you man ufw.