Better organization. Escape sequences. More gawk.
parent
5425627df1
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@ -64,20 +64,26 @@
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"daily/2024-01-31.md": "72e343cef8d56e169cac7b360a88fcf0",
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"posix/index.md": "f7b1ae55f8f5e8f50f89738b1aca9111",
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"posix/signals.md": "2120ddd933fc0d57abb93c33f639afd8",
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"gawk.md": "c79a09e1772da1d4f2cd296b7370ecab",
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"journal/2024-02-02.md": "a3b222daee8a50bce4cbac699efc7180",
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"algorithms/sorting/index.md": "cd189e1a2cf32b5656b16aaf9f488874",
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"algorithms/sorting/insertion-sort.md": "c78c9983f87cdc4198f82803d418967f",
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"algorithms/index.md": "1583c07edea4736db27c38fe2b6c4c31",
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"c/escape-sequences.md": "07f0811b0fff14f54f78abc33f2e6606",
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"journal/2024-02-03.md": "fca2323a3284ca8cd0a1aea9e354bb80",
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"c/index.md": "d41d8cd98f00b204e9800998ecf8427e",
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"gawk/variables.md": "4482c297e7f4f5987f42f1926a880ca7",
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"gawk/index.md": "0263448c8ae1ecfc0eacc4788f8402e9"
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},
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"fields_dict": {
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"Basic": [
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@ -8,7 +8,7 @@ tags:
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## Overview
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According to Robbins a POSIX-compliant shell (like Bash) generally has the primary and secondary prompts denoted with `$` and `>` respectively.
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According to Robbins a POSIX-compliant shell (like Bash) generally has the primary and secondary prompts denoted with `$` and `>` respectively. Adjust these values using environment variables `$PS1` and `PS2` respectively.
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%%ANKI
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Basic
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@ -18,6 +18,14 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 20
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<!--ID: 1706882670149-->
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END%%
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%%ANKI
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Basic
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What environment variable controls Bash's primary prompt?
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Back: `$$PS1`
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Reference: Cooper, Mendel. “Advanced Bash-Scripting Guide,” n.d., 916.
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<!--ID: 1706973587222-->
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END%%
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%%ANKI
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Basic
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What symbol is usually used to denote the secondary prompt?
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@ -26,6 +34,14 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 20
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<!--ID: 1706882670158-->
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END%%
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%%ANKI
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Basic
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What environment variable controls Bash's secondary prompt?
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Back: `$$PS2`
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Reference: Cooper, Mendel. “Advanced Bash-Scripting Guide,” n.d., 916.
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<!--ID: 1706973587232-->
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END%%
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Paths supplied to commands are typically "sanitized" by prefixing the path name with `./`. This is mentioned in a few different places:
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* `find -execdir` performs this prefixing automatically on all found files.
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@ -9,7 +9,7 @@ tags:
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## Overview
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An interesting point Robbins discusses in his introduction to [[gawk]] is this idea of command robustness. He states that:
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An interesting point Robbins discusses in his introduction to [[gawk/index|gawk]] is this idea of command robustness. He states that:
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> A self-contained shell script is more reliable because there are no other files to misplace.
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@ -56,6 +56,12 @@ It's interesting to think what else can be used as a measure of a command's robu
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* What happens if I run the command twice in a row?
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* Whether a program acts atomically
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* Is it possible intermediate files are left that affect subsequent runs?
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* The presence of timeouts
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* Perhaps a program waits a specified amount of time before input is available. The command's success is now externally determined.
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* Locale-aware functionality
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* 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.
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The above scenarios are what makes something like [[nix/index|nix]] so compelling.
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## References
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@ -0,0 +1,148 @@
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---
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title: Escape Sequences
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TARGET DECK: Obsidian::STEM
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FILE TAGS: c
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tags:
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- c
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---
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## Overview
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C has a standard for processing different escape sequences. Many languages built with C in mind parse these escape sequences in a similar way.
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* `\ooo`: Consists of one to three octal digits.
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* [[bash/index|Bash]] supports this sequence as `$'\ooo'`.
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* [[gawk/index|gawk]] supports this sequence directly.
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* [[lua/index|Lua]] does not support this kind of escape sequence. Instead, it has a *decimal* escape sequence `\ddd`.
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%%ANKI
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Basic
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How are C escape sequences for octal digits denoted?
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Back: As `\ooo`.
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Reference: Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
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<!--ID: 1706975891805-->
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END%%
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%%ANKI
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Basic
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In C, `\ooo` allows specifying how many octal digits?
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Back: One to three.
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Reference: Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
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<!--ID: 1706975891810-->
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END%%
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%%ANKI
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Basic
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What alternative does Lua provide to C's `\ooo` sequence?
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Back: `\ddd`, a *decimal* escape sequence.
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Reference: Roberto Ierusalimschy, _Programming in Lua_, Fourth edition (Rio de Janeiro: Lua.org, 2016).
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Tags: lua
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<!--ID: 1706975891813-->
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END%%
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%%ANKI
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Basic
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How are C escape sequences exposed in bash?
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Back: Using ANSI-C quoting, i.e. `$$'string'`.
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Reference: Mendel Cooper, “Advanced Bash-Scripting Guide,” n.d., 916.
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Tags: bash
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<!--ID: 1706975891817-->
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END%%
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* `\xhh`: Consists of one or more hexadecimal digits. The `x` prefix is required to distinguish from octal escape sequences.
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* [[bash/index|Bash]] supports this sequence as `$'\xhh'`. One or two digits is supported.
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* [[gawk/index|gawk]] limits processing to two digits.
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* Robbins states that using more than two hexadecimal digits can produce undefined results.
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* [[Lua/index|Lua]] requires *exactly* two digits in its hex escape sequence.
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%%ANKI
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Basic
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How are C escape sequences for hexadecimal digits denoted?
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Back: As `\xhh`.
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Reference: Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
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<!--ID: 1706975891820-->
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END%%
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%%ANKI
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Basic
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In C, `\x` allows specifying how many hexadecimal digits?
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Back: One or more.
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Reference: Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
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<!--ID: 1706975891824-->
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END%%
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%%ANKI
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Basic
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What footgun does C's `\x` sequence expose?
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Back: Using more than two hexadecimal digits can produce undefined results.
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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).
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<!--ID: 1706975891828-->
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END%%
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* `\uhhhh`: Introduced in C11 to represent Unicode code points. *Must* have exactly four hexadecimal characters specified with `0` leading padding if necessary.
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* [[bash/index|Bash]] supports this sequence as `$'uhhhh'`. One to four hex digits is supported.
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* [[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.
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* [[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.
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%%ANKI
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Basic
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What two ways are C escape sequences for unicode denoted?
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Back: As `\uhhhh` or `\Uhhhhhhhh`.
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Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
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Tags: unicode
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<!--ID: 1706975891832-->
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END%%
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%%ANKI
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Basic
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In C, `\u` allows specifying how many hexadecimal digits?
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Back: Exactly four.
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Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
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Tags: unicode
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<!--ID: 1706975891835-->
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END%%
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%%ANKI
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Basic
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In what standard were C's `\u` and `\U` escape sequences introduced?
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Back: C11.
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Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
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Tags: unicode
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<!--ID: 1706975891839-->
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END%%
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%%ANKI
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Cloze
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`\u` in C designates a character in {Unicode}. In `gawk` it designates a character in {the current locale's character set}.
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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).
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Tags: unicode gawk
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<!--ID: 1706976541399-->
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END%%
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* `\Uhhhhhhhh`: Introduced in C11 to represent larger unicode code points. *Must* have exactly eight hexadecimal characters specified with `0` leading padding if necessary.
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%%ANKI
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Basic
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In C, `\U` allows specifying how many hexadecimal digits?
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Back: Exactly eight.
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Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
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Tags: unicode
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<!--ID: 1706975891843-->
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END%%
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%%ANKI
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Basic
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Why does C have both `\u` and `\U`?
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Back: `\U` accommodates for larger code point values.
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Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
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Tags: unicode
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<!--ID: 1706976705750-->
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END%%
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## References
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* 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).
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* Brian W. Kernighan and Dennis M. Ritchie, _The C Programming Language_, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
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* Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
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* Mendel Cooper, “Advanced Bash-Scripting Guide,” n.d., 916.
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* Roberto Ierusalimschy, _Programming in Lua_, Fourth edition (Rio de Janeiro: Lua.org, 2016).
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@ -3,8 +3,6 @@ title: GAWK
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TARGET DECK: Obsidian::STEM
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FILE TAGS: linux::cli gawk
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tags:
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- linux
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- cli
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- gawk
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---
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@ -198,39 +196,12 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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<!--ID: 1706883732944-->
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END%%
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## Variables
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## Exit Status
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Variables are defined like `var=val`. They can be specified in two different places:
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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
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1. Via the `-v` command line flag. Using this allows accessing the variable value from within a `BEGIN` rule.
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2. In the file list. Using this allows accessing the variable value in all subsequent file processing.
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You can specify a custom exit status by using the `exit` statement from within the `awk` program.
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%%ANKI
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Basic
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Where in an `awk` invocation can variables be assigned?
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Back: As a `-v` argument or in the file list.
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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)
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<!--ID: 1706885111450-->
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END%%
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%%ANKI
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Basic
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The `-v` flag was introduced to accommodate what functionality?
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Back: Accessing variables from a `BEGIN` rule.
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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)
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<!--ID: 1706885111454-->
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END%%
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%%ANKI
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Basic
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Describe what the following command does in in a single sentence:
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```bash
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$ awk 'program' pass=1 data pass=2 data
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```
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Back: Evaluates `'program'` against the `data` file twice with a different value of `pass` on each run.
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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)
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<!--ID: 1706885111457-->
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END%%
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## References
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* 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)
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@ -0,0 +1,53 @@
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---
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title: GAWK
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TARGET DECK: Obsidian::STEM
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FILE TAGS: linux::cli gawk
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tags:
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- gawk
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---
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## Variables
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Variables are defined like `var=val`. They can be specified in two different places:
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1. Via the `-v` command line flag. Using this allows accessing the variable value from within a `BEGIN` rule.
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2. In the file list. Using this allows accessing the variable value in all subsequent file processing.
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%%ANKI
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Basic
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Where in an `awk` invocation can variables be assigned?
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Back: As a `-v` argument or in the file list.
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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)
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<!--ID: 1706885111450-->
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END%%
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%%ANKI
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Basic
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The `-v` flag was introduced to accommodate what functionality?
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Back: Accessing variables from a `BEGIN` rule.
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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)
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<!--ID: 1706885111454-->
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END%%
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%%ANKI
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Basic
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Describe what the following command does in in a single sentence:
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```bash
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$ awk 'program' pass=1 data pass=2 data
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```
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Back: Evaluates `'program'` against the `data` file twice with a different value of `pass` on each run.
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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)
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<!--ID: 1706885111457-->
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END%%
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%%ANKI
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Basic
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How is `stdin` specified in `awk`'s file list?
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Back: `-`
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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)
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<!--ID: 1706973587236-->
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END%%
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## References
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* 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)
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@ -0,0 +1,13 @@
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---
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title: "2024-02-03"
|
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---
|
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- [x] Anki Flashcards
|
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- [x] KoL
|
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- [ ] Sheet Music (10 min.)
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- [ ] OGS (1 Life & Death Problem)
|
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- [ ] Korean (Read 1 Story)
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- [ ] Interview Prep (1 Practice Problem)
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- [ ] Log Work Hours (Max 3 hours)
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* Spent time consolidating how different escape sequences behave across languages (`awk`, Bash, C, and Lua).
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@ -90,7 +90,7 @@ callPackage = callPackageWith pkgs;
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%%ANKI
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Basic
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What two functions is `callPackage` implemented on top of?
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Back: `callPackageWith` and `lib.makeOverridable`.
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Back: `callPackageWith` and `makeOverridable`.
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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)
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<!--ID: 1706828138592-->
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END%%
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@ -98,7 +98,7 @@ END%%
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%%ANKI
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Basic
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What is the purpose of `callPackage`?
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Back: It calls package functions with arguments automatic supplied if not overridden.
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Back: It calls package functions with arguments automatically supplied if not overridden.
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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)
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<!--ID: 1706828138594-->
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END%%
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@ -113,4 +113,4 @@ END%%
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## Reference
|
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|
||||
* 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)
|
||||
* 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)
|
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Reference in New Issue