nerdypepper's μblog

Termux Tandem

Sun, 08 Mar 20 16:47:00 +0000

I learnt about termux from a friend on IRC recently. +It looked super gimmicky to me at first, but it eventually +proved to be useful. Here's what I use it for:

+ +

rsync

+ +

Ever since I degoogled my android device, syncing files +between my phone and my PC has always been a pain. I’m +looking at you MTP. But, with termux and sshd all set up, +it's as simple as:

+ +

$ arp
+Address         HWtype  HWad ...
+192.168.43.187  ether   d0:0 ...
+
+$ rsync -avz 192.168.43.187:~/frogs ~/pics/frogs
+

+ +

ssh & tmux

+ +

My phone doubles as a secondary view into my main machine +with ssh and tmux. When I am away from my PC (read: +sitting across the room), I check build status and IRC +messages by sshing into a tmux session running the said +build or weechat.

+ +

file uploads

+ +

Not being able to access my (ssh-only) file host was +crippling. With a bash instance on my phone, I just copied +over my ssh keys, and popped in a file upload script (a +glorified scp). Now I just have to figure out a way to +clean up these file names …

+ +

~/storage/pictures/ $ ls
+02muf5g7b2i41.jpg  7alt3cwg77841.jpg  cl4bsrge7id11.png
+mtZabXG.jpg        p8d5c584f2841.jpg  vjUxGjq.jpg
+

+ +

cmus

+ +

Alright, I don't really listen to music via cmus, but I +did use it a couple times when my default music player was +acting up. cmus is a viable option:

+ +

Call To ARMs

Fri, 07 Feb 20 18:30:00 +0000

My 4th semester involves ARM programming. And proprietary +tooling (Keil C). But we don't do that here.

+ +

Building

+ +

Assembling and linking ARM binaries on non-ARM architecture +devices is fairly trivial. I went along with the GNU cross +bare metal toolchain binutils, which provides arm-as and +arm-ld (among a bunch of other utils that I don't care +about for now).

+ +

Assemble .s files with:

+ +

arm-none-eabi-as main.s -g -march=armv8.1-a -o main.out
+

+ +

The -g flag generates extra debugging information that +gdb picks up. The -march option establishes target +architecture.

+ +

Link .o files with:

+ +

arm-none-eabi-ld main.out -o main
+

+ +

Running (and Debugging)

+ +

Things get interesting here. gdb on your x86 machine +cannot read nor execute binaries compiled for ARM. So, we +simulate an ARM processor using qemu. Now qemu allows you +to run gdbserver on startup. Connecting our local gdb +instance to gdbserver gives us a view into the program’s +execution. Easy!

+ +

Run qemu, with gdbserver on port 1234, with our ARM +binary, main:

+ +

qemu-arm -singlestep -g 1234 main
+

+ +

Start up gdb on your machine, and connect to qemu’s +gdbserver:

+ +

(gdb) set architecture armv8-a
+(gdb) target remote localhost:1234
+(gdb) file main
+Reading symbols from main...  # yay!
+

+ +

GDB Enhanced

+ +

gdb is cool, but it's not nearly as comfortable as well +fleshed out emulators/IDEs like Keil. Watching registers, +CPSR and memory chunks update is pretty fun.

+ +

I came across gdb's TUI mode (hit C-x C-a or type tui +enable at the prompt). TUI mode is a godsend. It highlights +the current line of execution, shows you disassembly +outputs, updated registers, active breakpoints and more.

+ +

But, it is an absolute eyesore.

+ +

Say hello to GEF! “GDB +Enhanced Features” teaches our old dog some cool new tricks. +Here are some additions that made my ARM debugging +experience loads better:

+ +

Memory watches
Register watches, with up to 7 levels of deref (overkill, +I agree)
Stack tracing

+ +

And it's pretty! See for yourself:

+ +

Editing

+ +

Vim, with syntax off because it +dosen't handle GNU ARM syntax too well.

Color Conundrum

Mon, 30 Dec 19 18:30:00 +0000

This piece aims to highlight (pun intended) some of the +reasons behind my color +free editor setup.

+ +

Imagine highlighting an entire book because all of it is +important. That is exactly what (most) syntax highlighting +does. It is difficult for the human eye to filter out noise +in rainbow barf. Use color to draw attention, not diverge +it.

+ +

At the same time, a book devoid of color is boring! What +is the takeaway from this 10 line paragraph? What are the +technical terms used?

+ +

Prose and code are certainly different, but the fickle +minded human eye is the same. The eye constantly looks for a +frame of reference, a focal point. It grows tired when it +can't find one.

+ +

The following comparison does a better job of explaining +(none, ample and over-the-top highlighting, from left to +right):

+ +

Without highlighting (far left), it is hard to differentiate +between comments and code! The florid color scheme (far +right) is no good either, it contains too many attention +grabbers. The center sample is a healthy balance of both. +Function calls and constants stand out, and repetitive +keywords and other noise (let, as) are mildly dimmed +out. Comments and non-code text (sign column, status text) +are dimmed further.

+ +

I'll stop myself before I rant about color contrast and +combinations.

Static Sites With Bash

Fri, 22 Nov 19 18:30:00 +0000

After going through a bunch of static site generators +(pelican, +hugo, +vite), I decided to roll +my own. If you are more of the ‘show me the code’ kinda guy, +here you go.

+ +

Text formatting

+ +

I chose to write in markdown, and convert +to html with lowdown.

+ +

Directory structure

+ +

I host my site on GitHub pages, so +docs/ has to be the entry point. Markdown formatted posts +go into posts/, get converted into html, and end up in +docs/index.html, something like this:

+ +

posts=$(ls -t ./posts)     # chronological order!
+for f in $posts; do
+    file="./posts/"$f      # `ls` mangled our file paths
+    echo "generating post $file"
+
+    html=$(lowdown "$file")
+    echo -e "html" >> docs/index.html
+done
+

+ +

Assets

+ +

Most static site generators recommend dropping image +assets into the site source itself. That does have it’s +merits, but I prefer hosting images separately:

+ +

# strip file extension
+ext="${1##*.}"
+
+# generate a random file name
+id=$( cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 2 | head -n 1 )
+id="$id.$ext"
+
+# copy to my file host
+scp -P 443 "$1" emerald:files/"$id" 
+echo "https://u.peppe.rs/$id"
+

+ +

Templating

+ +

generate.sh +brings the above bits and pieces together (with some extra +cruft to avoid javascript). It uses sed to produce nice +titles from the file names (removes underscores, +title-case), and date(1) to add the date to each post +listing!

My Setup

Wed, 06 Nov 19 18:30:00 +0000

Decided to do one of these because everyone does one of +these.

+ +

My entire setup is managed with GNU stow, making it easier +to replicate on fresh installations. You can find my +configuration files on GitHub.

+ +

I run Void Linux (glibc) on my +HP Envy 13” (2018). +To keep things simple, I run a raw X session with 2bwm as my +window manager, along with dunst (notification daemon) and +Sam's compton +(compositor) fork.

+ +

I am a fan of GNU tools, so I use bash as my shell, and +coreutils to manage files, archives, strings, paths etc. I +edit files with vim, chat with weechat, listen to music +with cmus, monitor processes with htop, manage sessions +with tmux, read pdfs in zathura. I rarely ever leave +the comfort of my terminal emulator, urxvt.

+ +

Most of my academic typesetting is done with TeX, and +compiled with xelatex. Other fun documents are made with +GIMP :).

WPA Woes

Sat, 12 Oct 19 16:18:00 +0000

I finally got around to installing Void GNU/Linux on my main +computer. Rolling release, non-systemd, need I say more?

+ +

As with all GNU/Linux distributions, wireless networks had +me in a fix. If you can see this post, it means I've managed +to get online. It turns out, wpa_supplicant was detecting the +wrong interface by default (does it ever select the right +one?). Let us fix that:

+ +

$ sudo rm -r /var/service/wpa_supplicant
+$ sudo killall dhcpcd
+

+ +

What is the right interface though?

+ +

$ iw dev
+   ...
+   Interface wlp2s0
+   ...
+

+ +

Aha! Let us run wpa_supplicant on that interface, as a +background process:

+ +

$ sudo wpa_supplicant -B -i wlp2s0 -c /etc/wpa_supplicant/wpa_supplicant.conf
+$ sudo dhcpcd -B wlp2s0
+$ ping google.com
+PING ...
+

+ +

Yay! Make those changes perpetual by enabling the service:

+ +

------------------------------------------------------
+# Add these to /etc/wpa_supplicant/wpa_supplicant.conf
+OPTS="-B"
+WPA_INTERFACE="wlp2s0"
+------------------------------------------------------
+$ sudo ln -s /etc/sv/wpa_supplicant /var/service/
+$ sudo ln -s /etc/sv/dhcpcd /var/service/
+$ sudo sv restart wpa_supplicant
+$ sudo sv restart dhcpcd
+

Bye Bye BDFs

Wed, 07 Aug 19 12:31:00 +0000

Glyph Bitmap Distribution Format is no more, as the creators of +Pango, one of the most widely used text rendering +libraries, +announced +their plans for Pango 1.44.

+ +

Until recently, Pango used FreeType to draw fonts. They will be moving over +to Harfbuzz, an evolution of FreeType.

+ +

Why?

+ +

In short, FreeType was hard to work with. It required complex logic, and +provided no advantage over Harfbuzz (other than being able to fetch +opentype metrics with ease).

+ +

Upgrading to Pango v1.44 will break your GTK applications (if you use a +bdf/pcf bitmap font). Harfbuzz does support bitmap-only OpenType fonts, +otbs. Convert your existing fonts over to otbs using +FontForge. It is to be noted that applications +such as xterm and rxvt use xft (X FreeType) to render fonts, and will +remain unaffected by the update.

+ +

Both scientifica and +curie will soon ship with bitmap-only +OpenType font formats.

Onivim Sucks

Fri, 02 Aug 19 12:31:00 +0000

Onivim is a ‘modern modal editor’, combining fancy +interface and language features with vim-style modal editing. What's wrong you +ask?

+ +

Apart from buggy syntax highlighting, +broken scrolling and +others, +Onivim is proprietary software. It is licensed under a commercial +end user agreement license, +which prohibits redistribution in both object code and source code formats.

+ +

Onivim's core editor logic (bits that belong to vim), have been separated from +the interface, into libvim. libvim is +licensed under MIT, which means, this ‘extension’ of vim is perfectly in +adherence to vim's license text! +Outrun Labs are exploiting this loophole (distributing vim as a library) to +commercialize Onivim.

+ +

Onivim's source code is available on GitHub. +They do mention that the source code trickles down to the +oni2-mit repository, which (not yet) contains +MIT-licensed code, 18 months after each commit to the original repository.

+ +

Want to contribute to Onivim? Don't. They make a profit out of your contributions. +Currently, Onivim is priced at $19.99, ‘pre-alpha’ pricing which is 80% off the +final price! If you are on the lookout for an editor, I would suggest using +Vim, charity ware that actually works, and costs $100 lesser.

Bash Harder With Vim

Wed, 31 Jul 19 06:30:00 +0000

Bash is tricky, don't let your editor get in your way. Here's a couple of neat +additions you could make to your vimrc for a better shell programming +experience.

+ +

Man pages inside vim

+ +

Source this script to get started:

+ +

runtime ftplugin/man.vim
+

+ +

Now, you can open manpages inside vim with :Man! It adds nicer syntax highlighting +and the ability to jump around with Ctrl-] and Ctrl-T.

+ +

By default, the manpage is opened in a horizontal split, I prefer using a new tab:

+ +

let g:ft_man_open_mode = 'tab'
+

+ +

Scratchpad to test your commands

+ +

I often test my sed substitutions, here is +a sample from the script used to generate this site:

+ +

# a substitution to convert snake_case to Title Case With Spaces
+echo "$1" | sed -E -e "s/\..+$//g"  -e "s/_(.)/ \u\1/g" -e "s/^(.)/\u\1/g"
+

+ +

Instead of dropping into a new shell, just test it out directly from vim!

+ +

Yank the line into a register:
+ +
```
yy
+
```
Paste it into the command-line window:
+ +
```
q:p
+
```

Make edits as required:

+ +

syntax off            # previously run commands
+edit index.html       # in a buffer!
+w | so %
+!echo "new_post.md" | sed -E -e "s/\..+$//g"  --snip--
+^--- note the use of '!'
+

Hit enter with the cursor on the line containing your command!

+ +

$ vim
+New Post         # output
+Press ENTER or type command to continue
+

Hold Position!

Tue, 30 Jul 19 12:31:00 +0000

Often times, when I run a vim command that makes “big” changes to a file (a +macro or a :vimgrep command) I lose my original position and feel disoriented.

+ +

Save position with winsaveview()!

+ +

The winsaveview() command returns a Dictionary that contains information +about the view of the current window. This includes the cursor line number, +cursor coloumn, the top most line in the window and a couple of other values, +none of which concern us.

+ +

Before running our command (one that jumps around the buffer, a lot), we save +our view, and restore it once its done, with winrestview.

+ +

let view = winsaveview()
+s/\s\+$//gc              " find and (confirm) replace trailing blanks
+winrestview(view)        " restore our original view!
+

+ +

It might seem a little overkill in the above example, just use `` (double +backticks) instead, but it comes in handy when you run your file through +heavier filtering.

Get Better At Yanking And Putting In Vim

Mon, 29 Jul 19 12:31:00 +0000

reselecting previously selected text (i use this to fix botched selections):

+ +

gv  " :h gv for more
+    " you can use `o` in visual mode to go to the `Other` end of the selection
+    " use a motion to fix the selection
+

reselecting previously yanked text:

+ +

`[v`]
+`[         " marks the beginning of the previously yanked text   :h `[
+`]         " marks the end                                       :h `]
+ v         " visual select everything in between
+
+nnoremap gb `[v`]    " "a quick map to perform the above
+

pasting and indenting text (in one go):

+ +

]p   " put (p) and adjust indent to current line
+]P   " put the text before the cursor (P) and adjust indent to current line
+

$post_title

$post_date

$html