Better organization. Escape sequences. More gawk.

notes/.obsidian/plugins/obsidian-to-anki-plugin/data.json

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notes/bash/prompts.md

@@ -8,7 +8,7 @@ tags:
 
 ## Overview
 
-According to Robbins a POSIX-compliant shell (like Bash) generally has the primary and secondary prompts denoted with `$` and `>` respectively.
+According to Robbins a POSIX-compliant shell (like Bash) generally has the primary and secondary prompts denoted with `$` and `>` respectively. Adjust these values using environment variables `$PS1` and `PS2` respectively.
 
 %%ANKI
 Basic
@@ -18,6 +18,14 @@ Reference:  Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 20
 <!--ID: 1706882670149-->
 END%%
 
+%%ANKI
+Basic
+What environment variable controls Bash's primary prompt?
+Back: `$$PS1`
+Reference: Cooper, Mendel. “Advanced Bash-Scripting Guide,” n.d., 916.
+<!--ID: 1706973587222-->
+END%%
+
 %%ANKI
 Basic
 What symbol is usually used to denote the secondary prompt?
@@ -26,6 +34,14 @@ Reference:  Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 20
 <!--ID: 1706882670158-->
 END%%
 
+%%ANKI
+Basic
+What environment variable controls Bash's secondary prompt?
+Back: `$$PS2`
+Reference: Cooper, Mendel. “Advanced Bash-Scripting Guide,” n.d., 916.
+<!--ID: 1706973587232-->
+END%%
+
 Paths supplied to commands are typically "sanitized" by prefixing the path name with `./`. This is mentioned in a few different places:
 
 * `find -execdir` performs this prefixing automatically on all found files.

notes/bash/robustness.md

@@ -9,7 +9,7 @@ tags:
 
 ## Overview
 
-An interesting point Robbins discusses in his introduction to [[gawk]] is this idea of command robustness. He states that:
+An interesting point Robbins discusses in his introduction to [[gawk/index|gawk]] is this idea of command robustness. He states that:
 
 > A self-contained shell script is more reliable because there are no other files to misplace.
 
@@ -56,6 +56,12 @@ It's interesting to think what else can be used as a measure of a command's robu
 	* What happens if I run the command twice in a row?
 * Whether a program acts atomically
 	* Is it possible intermediate files are left that affect subsequent runs?
+* The presence of timeouts
+	* Perhaps a program waits a specified amount of time before input is available. The command's success is now externally determined.
+* Locale-aware functionality
+	* Consider for instance [[gawk/index|gawk]]'s `\u` [[escape-sequences|sequence]] which targets characters in the current locale's character set as opposed to specifically Unicode.
+
+The above scenarios are what makes something like [[nix/index|nix]] so compelling.
 
 ## References
 

notes/c/escape-sequences.md

@@ -0,0 +1,148 @@
+---
+title: Escape Sequences
+TARGET DECK: Obsidian::STEM
+FILE TAGS: c
+tags:
+  - c
+---
+
+## Overview
+
+C has a standard for processing different escape sequences. Many languages built with C in mind parse these escape sequences in a similar way.
+
+* `\ooo`: Consists of one to three octal digits.
+	* [[bash/index|Bash]] supports this sequence as `$'\ooo'`.
+	* [[gawk/index|gawk]] supports this sequence directly.
+	* [[lua/index|Lua]] does not support this kind of escape sequence. Instead, it has a *decimal* escape sequence `\ddd`.
+
+%%ANKI
+Basic
+How are C escape sequences for octal digits denoted?
+Back: As `\ooo`.
+Reference: Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
+<!--ID: 1706975891805-->
+END%%
+
+%%ANKI
+Basic
+In C, `\ooo` allows specifying how many octal digits?
+Back: One to three.
+Reference: Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
+<!--ID: 1706975891810-->
+END%%
+
+%%ANKI
+Basic
+What alternative does Lua provide to C's `\ooo` sequence?
+Back: `\ddd`, a *decimal* escape sequence.
+Reference: Roberto Ierusalimschy, _Programming in Lua_, Fourth edition (Rio de Janeiro: Lua.org, 2016).
+Tags: lua
+<!--ID: 1706975891813-->
+END%%
+
+%%ANKI
+Basic
+How are C escape sequences exposed in bash?
+Back: Using ANSI-C quoting, i.e. `$$'string'`.
+Reference: Mendel Cooper, “Advanced Bash-Scripting Guide,” n.d., 916.
+Tags: bash
+<!--ID: 1706975891817-->
+END%%
+
+* `\xhh`: Consists of one or more hexadecimal digits. The `x` prefix is required to distinguish from octal escape sequences.
+	* [[bash/index|Bash]] supports this sequence as `$'\xhh'`. One or two digits is supported.
+	* [[gawk/index|gawk]] limits processing to two digits.
+		* Robbins states that using more than two hexadecimal digits can produce undefined results.
+	* [[Lua/index|Lua]] requires *exactly* two digits in its hex escape sequence.
+
+%%ANKI
+Basic
+How are C escape sequences for hexadecimal digits denoted?
+Back: As `\xhh`.
+Reference: Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
+<!--ID: 1706975891820-->
+END%%
+
+%%ANKI
+Basic
+In C, `\x` allows specifying how many hexadecimal digits?
+Back: One or more.
+Reference: Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
+<!--ID: 1706975891824-->
+END%%
+
+%%ANKI
+Basic
+What footgun does C's `\x` sequence expose?
+Back: Using more than two hexadecimal digits can produce undefined results.
+Reference: Arnold D. Robbins, “GAWK: Effective AWK Programming,” October 2023, [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf).
+<!--ID: 1706975891828-->
+END%%
+
+* `\uhhhh`: Introduced in C11 to represent Unicode code points. *Must* have exactly four hexadecimal characters specified with `0` leading padding if necessary.
+	* [[bash/index|Bash]] supports this sequence as `$'uhhhh'`. One to four hex digits is supported.
+	* [[gawk/index|gawk]] consolidates C's `\u` and `\U` sequence marker into just `\u`, capable of handling one to eight digits. Furthermore, `gawk` uses `\u` to designate the current locale's character set, *not* Unicode directly. Often times this is some Unicode-based locale though.
+	* [[lua/index|Lua]] consolidates C's `\u` and `\U` sequence markers into `\u{h...h}`, capable of handling one or more hexadecimal digits. The curly braces are required.
+
+%%ANKI
+Basic
+What two ways are C escape sequences for unicode denoted?
+Back: As `\uhhhh` or `\Uhhhhhhhh`.
+Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
+Tags: unicode
+<!--ID: 1706975891832-->
+END%%
+
+%%ANKI
+Basic
+In C, `\u` allows specifying how many hexadecimal digits?
+Back: Exactly four.
+Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
+Tags: unicode
+<!--ID: 1706975891835-->
+END%%
+
+%%ANKI
+Basic
+In what standard were C's `\u` and `\U` escape sequences introduced?
+Back: C11.
+Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
+Tags: unicode
+<!--ID: 1706975891839-->
+END%%
+
+%%ANKI
+Cloze
+`\u` in C designates a character in {Unicode}. In `gawk` it designates a character in {the current locale's character set}.
+Reference: Arnold D. Robbins, “GAWK: Effective AWK Programming,” October 2023, [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf).
+Tags: unicode gawk
+<!--ID: 1706976541399-->
+END%%
+
+* `\Uhhhhhhhh`: Introduced in C11 to represent larger unicode code points. *Must* have exactly eight hexadecimal characters specified with `0` leading padding if necessary.
+
+%%ANKI
+Basic
+In C, `\U` allows specifying how many hexadecimal digits?
+Back: Exactly eight.
+Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
+Tags: unicode
+<!--ID: 1706975891843-->
+END%%
+
+%%ANKI
+Basic
+Why does C have both `\u` and `\U`?
+Back: `\U` accommodates for larger code point values.
+Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
+Tags: unicode
+<!--ID: 1706976705750-->
+END%%
+
+## References
+
+* Arnold D. Robbins, “GAWK: Effective AWK Programming,” October 2023, [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf).
+* Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
+* Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
+* Mendel Cooper, “Advanced Bash-Scripting Guide,” n.d., 916.
+* Roberto Ierusalimschy, _Programming in Lua_, Fourth edition (Rio de Janeiro: Lua.org, 2016).

notes/gawk/index.md

@@ -3,8 +3,6 @@ title: GAWK
 TARGET DECK: Obsidian::STEM
 FILE TAGS: linux::cli gawk
 tags:
-  - linux
-  - cli
   - gawk
 ---
 
@@ -198,39 +196,12 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
 <!--ID: 1706883732944-->
 END%%
 
-## Variables
+## Exit Status
 
-Variables are defined like `var=val`. They can be specified in two different places:
+On success, `gawk` exits with status code `EXIT_SUCCESS`. On failure, with status code `EXIT_FAILURE`. On fatal error, `gawk` exists with status code `2`. #c
 
-1. Via the `-v` command line flag. Using this allows accessing the variable value from within a `BEGIN` rule.
+You can specify a custom exit status by using the `exit` statement from within the `awk` program.
-2. In the file list. Using this allows accessing the variable value in all subsequent file processing.
 
-%%ANKI
-Basic
-Where in an `awk` invocation can variables be assigned?
-Back: As a `-v` argument or in the file list.
-Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)
-<!--ID: 1706885111450-->
-END%%
-
-%%ANKI
-Basic
-The `-v` flag was introduced to accommodate what functionality?
-Back: Accessing variables from a `BEGIN` rule.
-Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)
-<!--ID: 1706885111454-->
-END%%
-
-%%ANKI
-Basic
-Describe what the following command does in in a single sentence:
-```bash
-$ awk 'program' pass=1 data pass=2 data
-```
-Back: Evaluates `'program'` against the `data` file twice with a different value of `pass` on each run.
-Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)
-<!--ID: 1706885111457-->
-END%%
 ## References
 
 * Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)

notes/gawk/variables.md

@@ -0,0 +1,53 @@
+---
+title: GAWK
+TARGET DECK: Obsidian::STEM
+FILE TAGS: linux::cli gawk
+tags:
+  - gawk
+---
+
+## Variables
+
+Variables are defined like `var=val`. They can be specified in two different places:
+
+1. Via the `-v` command line flag. Using this allows accessing the variable value from within a `BEGIN` rule.
+2. In the file list. Using this allows accessing the variable value in all subsequent file processing.
+
+%%ANKI
+Basic
+Where in an `awk` invocation can variables be assigned?
+Back: As a `-v` argument or in the file list.
+Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)
+<!--ID: 1706885111450-->
+END%%
+
+%%ANKI
+Basic
+The `-v` flag was introduced to accommodate what functionality?
+Back: Accessing variables from a `BEGIN` rule.
+Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)
+<!--ID: 1706885111454-->
+END%%
+
+%%ANKI
+Basic
+Describe what the following command does in in a single sentence:
+```bash
+$ awk 'program' pass=1 data pass=2 data
+```
+Back: Evaluates `'program'` against the `data` file twice with a different value of `pass` on each run.
+Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)
+<!--ID: 1706885111457-->
+END%%
+
+%%ANKI
+Basic
+How is `stdin` specified in `awk`'s file list?
+Back: `-`
+Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)
+<!--ID: 1706973587236-->
+END%%
+
+## References
+
+* Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)

notes/journal/2024-02-03.md

@@ -0,0 +1,13 @@
+---
+title: "2024-02-03"
+---
+
+- [x] Anki Flashcards
+- [x] KoL
+- [ ] Sheet Music (10 min.)
+- [ ] OGS (1 Life & Death Problem)
+- [ ] Korean (Read 1 Story)
+- [ ] Interview Prep (1 Practice Problem)
+- [ ] Log Work Hours (Max 3 hours)
+
+* Spent time consolidating how different escape sequences behave across languages (`awk`, Bash, C, and Lua).

notes/nix/callPackage.md

@@ -90,7 +90,7 @@ callPackage = callPackageWith pkgs;
 %%ANKI
 Basic
 What two functions is `callPackage` implemented on top of?
-Back: `callPackageWith` and `lib.makeOverridable`.
+Back: `callPackageWith` and `makeOverridable`.
 Reference: Yin, Ryan. “NixOS and Flakes Book.” Nix, February 1, 2024. [https://github.com/ryan4yin/nixos-and-flakes-book](https://github.com/ryan4yin/nixos-and-flakes-book)
 <!--ID: 1706828138592-->
 END%%
@@ -98,7 +98,7 @@ END%%
 %%ANKI
 Basic
 What is the purpose of `callPackage`?
-Back: It calls package functions with arguments automatic supplied if not overridden. 
+Back: It calls package functions with arguments automatically supplied if not overridden. 
 Reference: Yin, Ryan. “NixOS and Flakes Book.” Nix, February 1, 2024. [https://github.com/ryan4yin/nixos-and-flakes-book](https://github.com/ryan4yin/nixos-and-flakes-book)
 <!--ID: 1706828138594-->
 END%%