Update my notebook as of 2021-06-06

2020-09-15-03-08-22.org

@@ -1,12 +0,0 @@
-:PROPERTIES:
-:ID:       15d394fc-2104-4193-af31-f16da1661758
-:END:
-#+title: Create package definitions for missing dependencies first before the package itself
-#+date: "2020-09-15 03:08:22 +08:00"
-#+date_modified: "2021-05-04 20:52:08 +08:00"
-#+language: en
-
-
-Certain ecosystems like in [[id:3b3fdcbf-eb40-4c89-81f3-9d937a0be53c][Nix package manager]] with [[https://github.com/NixOS/nixpkgs][nixpkgs]] or [[id:be917383-84c4-4bf5-9ca0-b04bfb778f4f][GNU Guix]] within their own packages follow a standard (officially) [fn:: If not, you can freely ~make build~ all you want.] about making sure all dependencies are present first before building the package.
-Smaller libraries often go through this and so, you need to package the dependencies first.
-It also helps with creating a global definition for other packages that requires those small libraries.

structured/assets/cli.borg/safe-borg-backup

@@ -0,0 +1,8 @@
+#/usr/bin/env bash
+if $# -eq 1; then echo "No directories and files to be saved." && exit 1; fi
+
+locations=$@
+
+borg create --verbose --stats --compression lz4 --exclude '**/.node_modules' ::{hostname}-{now:%F-%H-%M-%S-%z} ${locations[@]}
+borg check --verbose --verify-data
+borg prune --verbose --keep-daily 7 --keep-hourly 7 --keep-weekly 6 --keep-monthly 6

structured/cli.borg.org

@@ -3,8 +3,9 @@
 :END:
 #+title: BorgBackup
 #+date: "2021-05-30 21:40:24 +08:00"
-#+date_modified: "2021-06-04 21:47:36 +08:00"
+#+date_modified: "2021-06-05 09:11:53 +08:00"
 #+language: en
+#+property: header_args :eval no
 #+property: header_args:bash  :results silent  :exports code
 
 
@@ -63,7 +64,7 @@ ${REPOSITORY_URL}::${ARCHIVE_NAME}
 You can also refer to a name dynamically with placeholders.
 
 #+begin_src
-/home/foo-dogsquared/backup::{hostname}-{user}-{now}
+/home/{user}/backup::{hostname}-{user}-{now}
 #+end_src
 
 For more information, you can see the related section for Borg placeholders.
@@ -125,8 +126,8 @@ borg extract --verbose --progress ${REPO_PATH}::{hostname}-{now:%F-%T-%z} ~/Docu
 Better be safe than sorry.
 Here's the safe backup in all of its glory in Bash.
 
-#+begin_src bash  :file safe-borg-backup  :shebang '/usr/bin/env bash'
-if $# -eq 0; then echo "No directories and files to be saved." && exit 1; fi
+#+begin_src bash  :tangle (my/concat-assets-folder "safe-borg-backup")  :shebang "#/usr/bin/env bash"
+if $# -eq 1; then echo "No directories and files to be saved." && exit 1; fi
 
 locations=$@
 
@@ -135,6 +136,8 @@ borg check --verbose --verify-data
 borg prune --verbose --keep-daily 7 --keep-hourly 7 --keep-weekly 6 --keep-monthly 6
 #+end_src
 
+#+results:
+
 Since the script only lets you enter arguments used for saving into the archive, you have to use environment variables.
 
 #+begin_src shell

structured/cli.niv.org

@@ -1,6 +1,9 @@
+:PROPERTIES:
+:ID:       c05e1aa9-0619-4617-abb6-870fceca3430
+:END:
 #+title: Niv
 #+date: "2021-05-09 17:25:04 +08:00"
-#+date_modified: "2021-05-09 17:25:23 +08:00"
+#+date_modified: "2021-06-05 12:36:39 +08:00"
 #+language: en
 
 

structured/editor.vim.org

@@ -0,0 +1,64 @@
+#+title: Vim
+#+date: "2021-06-06 05:12:20 +08:00"
+#+date_modified: "2021-06-06 14:07:26 +08:00"
+#+language: en
+
+
+Every sysadmin's favorite default text editor.
+Is being familiar to Vim a path to productivity?
+No.
+But being good at it can make for a difference in the day-to-day life of a sysadmin for there are advanced capabilities of this editor.
+
+
+
+
+
+
+
+* The keybindings of Vim
+
+One of the things that make Vim popular is the keybindings.
+
+| Keybinding | Description                                |
+|------------+--------------------------------------------|
+| =[m=       | Go to the previous method.                 |
+| =g~w=      | Toggle letter casing.                      |
+| =2guW=     | Convert two words into lowercase.          |
+| =10d)=     | Delete 10 sentences.                       |
+| =39zz=     | Place the cursor in the middle in line 39. |
+| =3d10w=    | Delete 10 words and repeat 3 times.        |
+
+Most of the time, Vim keybindings is made of mainly two things:
+
+- *The operators denoting an action.*
+- *The motions describing the scope of the action.*
+
+There's a certain pattern to it when you use it, too.
+
+#+begin_src
+[count][operator][motion]
+#+end_src
+
+
+
+
+* Tips and tricks
+
+- =:h= is the help system of Vim.
+  It contains all of the documentation of the editor and the installed plugins.
+  I recommend to start with the default help page (e.g., =:h=).
+
+  + You can get the meaning of the keybinding with the help section — e.g., ~:h gg~, ~:h G~.
+
+- Vim has fine-grained control motions.
+  + =(= and =)= for sentences.
+  + ={= and =}= for paragraphs.
+  + =[= and =]= for sections.
+
+- There are many advanced navigation features in Vim.
+  + =gf= will go to the file at point.
+  + =K= goes to the definition of the keyword at point.
+  + =Ctrl+O= will jump back at a previous jump point.
+  + =gd= go the local definition of the keyword at point.
+  + =H=, =M=, and =L= places the cursor in higher, middle, and lower part in the current screen, respectively.
+  + =zt=, =zz=, and =zb= displays the current line in the top, middle, and bottom part of the screen, respectively.

structured/lang.oil.org

@@ -1,11 +1,12 @@
 #+title: Oil shell
 #+date: "2021-05-09 16:40:50 +08:00"
-#+date_modified: "2021-06-04 21:55:38 +08:00"
+#+date_modified: "2021-06-05 16:36:01 +08:00"
 #+language: en
+#+property: header-args:oil  :eval no
 
 
 For future references, this note mainly notes Oil v0.8.11 and later versions.
-
+Also, we'll be comparing to Bash shell (src_bash[:eval yes  :results output]{bash --version}) as it is the most popular shell on the Unix world.
 
 
 
@@ -67,6 +68,33 @@ for i in @keywords { echo "keyword: $i" }
 #+end_src
 
 
+** Strings
+
+While strings are similar to Bash strings [fn:: Really more like Python strings.], there are subtle differences.
+Most notably, Bash splits the string when trying to do something.
+
+#+begin_src bash
+d='echo 3'
+e='echo "The quick brown fox jumps over the lazy dog."'
+
+parallel -- $d $e
+#+end_src
+
+It should throw an error because =parallel= interprets it as if it has 4 arguments due to the splitting — i.e., ~parallel -- echo 3 echo "The quick brown fox jumps over the lazy dog."~.
+The solution here is to quote the variables in evaluation (e.g., ~parallel -- "$d" "$e"~).
+
+Compare that to Oil...
+
+#+begin_src oil
+var d = 'echo 3'
+var e = 'echo "The quick brown fox jumps over the lazy dog."'
+
+parallel -- $d $e
+#+end_src
+
+If you want splitting, you could use =split= Oil function — e.g., ~@split(array_var)~.
+
+
 ** Arrays
 
 Arrays are mostly similar to Bash arrays except you have more options.
@@ -94,6 +122,24 @@ _ a.append("biz")
 #+end_src
 
 
+** Conditionals
+
+#+begin_src oil
+# Ternary conditionals
+echo $['dogs' if dogs == 'cute' else 'cats']
+
+# If-else statements
+if (4 == 5) {
+  echo "Alright, this is true."
+} elif (1 > 5) {
+  echo "Another condition?"
+} else {
+  echo "It seems you got me."
+}
+#+end_src
+
+
+
 
 
 * Expression and command mode
@@ -115,3 +161,13 @@ _ a.append("biz")
   + the === command where it will print the results — e.g., ~= 53~
   + you can interpolate expression mode expressions with =$[]= — e.g., ~echo $[4 + 43 + a]~, ~echo $[len(ARGV)]~
   + in =if= statements — e.g., ~if (true) { echo "WHOA" }~
+
+
+
+
+* Tips and tricks
+
+- Oil seems to evaluate in applicative order, evaluating only when the conditions passed — e.g., ~echo $['' + null if null else 'EEEEHHH']~ should print =EEEEHHH=.
+  + Just like most modern mainstream languages... nice.
+- Two operands of different types are considered unequal — e.g., ~'4' == 4~.
+  + You can use Python-like type conversions like =Int=, =Bool=, and =Str= — e.g., ~Int('4') == 4~.

structured/linux.installation.org

@@ -0,0 +1,15 @@
+#+title: Summary of a Linux installation
+#+date: "2021-06-05 22:30:48 +08:00"
+#+date_modified: "2021-06-05 22:32:56 +08:00"
+#+language: en
+
+
+# TODO: Improve note
+- initial setup
+- partitioning
+- installation of the operating system
+  + base package set
+  + feature-specific packages
+  + boot loader
+  + network manager
+  + init system

structured/tools.nix.org

@@ -0,0 +1,55 @@
+:PROPERTIES:
+:ID:       892676b3-76cb-4cd4-9689-910c1fe6587a
+:END:
+#+title: The basics of Nix package manager
+#+date: "2021-06-05 12:34:49 +08:00"
+#+date_modified: "2021-06-05 13:32:22 +08:00"
+#+language: en
+
+
+
+[[id:3b3fdcbf-eb40-4c89-81f3-9d937a0be53c][Nix package manager]] is a great tool for reproducibility as you can easily set up your environment.
+Taking it up to the next level with NixOS, your whole installation.
+
+
+
+
+* Ecosystem
+
+- Nix has tools to make setting up environments easier with direnv, lorri, and [[id:c05e1aa9-0619-4617-abb6-870fceca3430][Niv]]
+
+You can create a [[https://nix.dev/tutorials/ad-hoc-developer-environments#reproducible-executables][reproducible executable]] that only requires Nix.
+
+#+begin_src bash
+#!/usr/bin/env nix-shell
+#! nix-shell --pure -i bash -p curl jq fzf findutils
+
+# A quick command line interface for creating a gitignore with the API from https://gitignore.io.
+# This script comes with a simple caching to avoid creating too much requests.
+
+set -eo pipefail
+
+CACHE_FILE="${XDG_CACHE_DIR:-$HOME/.cache}/gitignore-io.langs.json"
+
+# Check if the language list is downloaded for the last hour (3600 seconds).
+if [ ! -e $CACHE_FILE ] || test $(expr $(date "+%s") - $(date -r $CACHE_FILE "+%s")) -gt 3600
+then
+    ping "gitignore.io" --count 4 && curl --silent --location --output $CACHE_FILE "https://gitignore.io/api/list?format=json"
+fi
+
+KEYS=$(jq 'keys | .[] | @text' --raw-output $CACHE_FILE | fzf --multi | while read lang; do echo " .[\"$lang\"].contents"; done | paste -s -d ',')
+
+jq "$KEYS" --raw-output $CACHE_FILE
+#+end_src
+
+
+
+
+* Components of the package manager
+
+Holistically, Nix is made up of at least four components: the store, the language, the derivations, and the sandbox.
+
+- The store is a immutable centralized location where all of the outputs are placed.
+- The derivations are essentially build instructions.
+- The language (also called as Nix but we'll refer to it as Nixlang) is a domain-specific language for creating derivations.
+- The build process can be locked in a sandbox, improving the reproducibility of a setup and lowering the attack surface for a malicious package.