Add more gawk flashcards.
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@ -60,14 +60,17 @@
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"Linux/Signals.md": "f58f1a36a9fe53928fdc3dc02fc4c3e3",
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"linux/index.md": "6e50c924ee9e09294fd3b907fbdeaf0f",
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"linux/signals.md": "e9ab74723981ebc232189c84d3b0da74",
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"templates/daily.md": "0f22c7ef0b0f35efada88d61c95e9815",
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"templates/daily.md": "7866014e730e85683155207a02e367d8",
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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": "26161c6a79a0c413032c6c17e460412c",
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"gawk.md": "9bf70ef138a9a281b86400aee393cae7",
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"posix/signals.md": "2120ddd933fc0d57abb93c33f639afd8",
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"gawk.md": "c0cf6decdf02f5513e386525b02bdf58",
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"bash/index.md": "3b5296277f095acdf16655adcdf524af",
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"bash/shebang.md": "bc30f75bcddff59d6f907fae89c17283",
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"bash/robustness.md": "e474fd33469fc393bfde45cd7b9411ba"
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"bash/shebang.md": "ad178efeb4a05190b80b5df108c175c7",
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"bash/robustness.md": "de97cd77aae047b5eea27440b43c9c42",
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"journal/2024-02-01.md": "f4cc061bfc8e41ce15ae9a354c65ffe9",
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"journal/2024-01-31.md": "7c7fbfccabc316f9e676826bf8dfe970",
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"bash/quoting.md": "8086c0a576f30d77248faac16a4be79e"
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},
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"fields_dict": {
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"Basic": [
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@ -0,0 +1,47 @@
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---
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title: Quoting
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TARGET DECK: Obsidian::STEM
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FILE TAGS: bash
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tags:
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- bash
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---
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%%ANKI
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Basic
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How do you escape a `'` within a single-quote string?
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Back: This is impossible.
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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: 1706816752230-->
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END%%
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%%ANKI
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Basic
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What does the null string refer to?
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Back: The empty string, i.e. `""`.
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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: 1706816752237-->
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END%%
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%%ANKI
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Basic
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When does Bash remove null strings from a command?
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Back: When they occur as part of a non-null command-line argument.
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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: 1706816752241-->
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END%%
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%%ANKI
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Basic
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What is wrong with the following command?
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```bash
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$ # -F specifies the field separator
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$ awk -F"" 'program' files
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```
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Back: Bash removes the null string before executing the command.
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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: 1706816764555-->
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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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@ -7,7 +7,9 @@ tags:
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- shell
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---
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An interesting point Robbins[^robbins] discusses in his introduction to [[gawk]] is this idea of command robustness. He states that:
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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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> A self-contained shell script is more reliable because there are no other files to misplace.
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@ -27,7 +29,7 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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<!--ID: 1706726911475-->
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END%%
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The point he is arguing is that the first command below is considered more robust than the second since the command is more loosely coupled to its environment:
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He argues that the first command below is more robust than the second since the command is more loosely coupled to its environment:
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```bash
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$ awk 'program' input-file1 input-file2 ...
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@ -55,4 +57,6 @@ It's interesting to think what else can be used as a measure of a command's robu
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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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[^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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## 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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@ -6,6 +6,8 @@ tags:
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- bash
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---
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## Overview
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The shebang (also writting shabang or sha-bang) is a magic character at the start of a script indicating what command should be run when invoking the script directly. It always begins with ASCII characters `#!`.[^mendel]
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%%ANKI
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@ -44,12 +46,13 @@ Some systems limit the length of interpreters to just 32 characters. A simple wo
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%%ANKI
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Basic
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What workaround is used when shabang interpreter names are too long?
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What workaround is used when shebang interpreter names are too long?
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Back: Introduce a symbolic link.
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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: 1706726911470-->
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END%%
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[^mendel]: Cooper, Mendel. “Advanced Bash-Scripting Guide,” n.d., 916.
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## References
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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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* Cooper, Mendel. “Advanced Bash-Scripting Guide,” n.d., 916.
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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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113
notes/gawk.md
113
notes/gawk.md
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@ -8,7 +8,7 @@ tags:
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- gawk
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---
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## Introduction
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## Overview
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%%ANKI
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Basic
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@ -25,7 +25,7 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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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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> Dark corners are basically fractal - no matter how much you illuminate, there's always a smaller but darker one. #quote
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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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@ -83,4 +83,111 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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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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%%ANKI
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Basic
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Write the `awk` command that searches file `mail-list` for string `li`.
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Back:
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```bash
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$ awk '/li/ { print }' mail-list
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```
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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: 1706819150999-->
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END%%
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%%ANKI
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Basic
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How is an `awk` rule without a pattern interpreted?
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Back: As applying the specified action for every input line.
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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: 1706822165633-->
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END%%
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%%ANKI
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Basic
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How is an `awk` rule without an action interpreted?
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Back: As printing every line matching the specified pattern.
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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: 1706822165637-->
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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 'length($0) > 80' data
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```
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Back: Prints every line of `data` that is longer than `80` characters.
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Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf)
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<!--ID: 1706822165641-->
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END%%
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**Targets** are specified as `$n` where `n` is a placeholder for the `n`th whitespace-separated **field**s of the input line. For example, `$1` refers to the first field of the input line. `$0` is a special target referring to the entire list of arguments, i.e. the entire line.
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%%ANKI
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Basic
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What is `$0` a placeholder for?
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Back: The entire input line.
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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: 1706823790230-->
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END%%
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%%ANKI
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Basic
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What is `$1` a placeholder for?
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Back: The first field of the input line.
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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: 1706823790233-->
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END%%
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%%ANKI
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Basic
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What is the `BEGIN` pattern?
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Back: Code associated with it executes before any input is read.
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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: 1706823790236-->
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END%%
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%%ANKI
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Basic
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What is the `END` pattern?
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Back: Code associated with it executes after all input has been read.
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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: 1706823790239-->
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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 'NF > 0' data
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```
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Back: Prints every line of `data` with at least one field.
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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: 1706823927382-->
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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 'END { print NR }' data
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```
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Back: Prints the number of lines in `data`.
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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: 1706824091124-->
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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 'NR % 2 == 0' data
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```
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Back: Prints every even-numbered line in `data`.
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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: 1706824091128-->
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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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@ -7,7 +7,9 @@ tags:
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- signal
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---
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This is an overview of specific POSIX signals.[^dowling]
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## Overview
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This is an overview of specific POSIX signals.
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Code | Name
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----- | --------------
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@ -112,4 +114,33 @@ Reference: `man 1 ps`
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<!--ID: 1706670390919-->
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END%%
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[^dowling]: Dowling, “A List of Signals and What They Mean.”
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### SIGINT (2)
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Indicates the process was interrupted by the user. Happens when pressing `Ctrl-C` from the controlling terminal.
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%%ANKI
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Cloze
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Signal {`SIGINT`} corresponds to number {2}.
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706815743860-->
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END%%
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%%ANKI
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Basic
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What control sequence usually triggers a `SIGINT`?
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Back: `Ctrl-C`
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706815743867-->
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END%%
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%%ANKI
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Basic
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What is the `INT` in `SIGINT` short for?
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Back: **Int**errupt
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706815743870-->
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END%%
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## References
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* Dowling, “A List of Signals and What They Mean.”
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