87 lines
3.1 KiB
Markdown
87 lines
3.1 KiB
Markdown
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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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- linux
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- cli
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- gawk
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---
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## Introduction
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%%ANKI
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Basic
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How was the name `awk` derived?
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Back: By taking the first initials of the original three creators.
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<!--ID: 1706726911434-->
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END%%
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%%ANKI
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Basic
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What does the term `awk` refer to?
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Back: Both the `awk` program and the `awk` language.
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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: 1706726911439-->
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END%%
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> Dark corners are basically fractal - no matter how much you illuminate, there's always a smaller but darker one.
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The above quote is attributed to Brian Kernighan (one of the authors of the [[C]] K&R book).
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%%ANKI
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Cloze
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Dark corners are basically {1:fractal} - {1:no matter how much you illuminate, there's always a smaller but darker one.} - Brian Kernighan
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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: 1706726911442-->
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END%%
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## Setup
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Robbins[^robbins] suggests executing command `set +H` on [[bash]] startup to disable [[C]] shell-style command history.
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## Usage
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`awk` applies actions to lines matching specified patterns. In this way `awk` is said to be data-driven - we specify the lines `awk` should act on and `awk` is responsible for finding and acting on them. Instructions are provided via a **program**.
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%%ANKI
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Basic
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What is the basic function of `awk`?
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Back: To apply actions to lines matching specified patterns.
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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: 1706726911445-->
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END%%
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An `awk` program consists of **rules**, each made up by a **pattern** and **action**. For example:
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```awk
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BEGIN { print "hello world" }
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pattern { action }
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```
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%%ANKI
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Basic
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An `awk` program consists of a series of what?
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Back: Rules.
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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: 1706726911448-->
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END%%
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%%ANKI
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Basic
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A rule found in an `awk` program consists of what two parts?
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Back: A pattern and an action.
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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: 1706726911451-->
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END%%
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%%ANKI
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Basic
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A standalone `awk` program usually has what shebang?
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Back: `#!/bin/awk -f`
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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: 1706726911454-->
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END%%
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[^robbins]: 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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