Begin 2024-02-13 entry.
parent
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"bash/shebang.md": "9006547710f9a079a3666169fbeda7aa",
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"c/escape-sequences.md": "0d6219ebb51f6f21e026de67603e25b8",
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"c/index.md": "a021c92f19831bdd2bca4cbf813882fe",
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"gawk/index.md": "0a305a0477085fd2f4145536735ca94a",
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"gawk/variables.md": "7408f450957ab007fbdbd687121da0d3",
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"gawk/index.md": "dd851e023e11c556c0272a0dcb6dd55d",
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"gawk/variables.md": "a9cd0344390974b3bfdf794d75d434e5",
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"index.md": "e48e895feeed7046425bb2ee15419770",
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"journal/2024-01-31.md": "7c7fbfccabc316f9e676826bf8dfe970",
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"journal/2024-02-01.md": "3aa232387d2dc662384976fd116888eb",
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@ -152,7 +152,9 @@
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"c/strings.md": "38f9cf9e2325565589f62e191221a83a",
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"logic/truth-tables.md": "7892ceaa416c9a65acc79ca1e6ff778f",
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"logic/short-circuit.md": "26d300f407f14883022d0ef8dc4f7300",
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"logic/boolean-algebra.md": "c5d699d407e03d280aa1f201bc3e8b02"
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"logic/boolean-algebra.md": "c5d699d407e03d280aa1f201bc3e8b02",
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"_journal/2024-02-13.md": "75ba5d7d77862c50a172a59415ec6a84",
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"_journal/2024-02/2024-02-12.md": "618c0035a69b48227119379236a02f44"
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},
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"fields_dict": {
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"Basic": [
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---
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title: "2024-02-13"
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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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* Read more on record and field separators in `gawk`.
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@ -27,13 +27,6 @@ END%%
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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 suggests executing command `set +H` on [[bash]] startup to disable [[C]] shell-style command history.
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@ -129,14 +122,6 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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<!--ID: 1707310981378-->
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END%%
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%%ANKI
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Basic
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What is the default record separator?
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Back: The newline character.
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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: 1707310981380-->
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END%%
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%%ANKI
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Basic
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In `awk`, what does a "field" refer to?
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@ -73,25 +73,9 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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<!--ID: 1707405259925-->
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END%%
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* `RS` (**R**ecord **S**eparator)
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* The separator used to distinguish records from one another.
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* `RT` (**R**ecord **T**ext)
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* The matching separator used to distinguish the currently read record.
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%%ANKI
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Cloze
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The {`RS`} variable is used to change the {record separator}.
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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: 1707310981382-->
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END%%
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%%ANKI
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Cloze
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If `RS` is a string with {more than one character}, it is treated as a {regexp}.
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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: 1707310981384-->
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END%%
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%%ANKI
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Cloze
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The {`RT`} variable matches the {input characters that matched `RS`}.
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@ -107,6 +91,39 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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<!--ID: 1707310981388-->
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END%%
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* `RS` (**R**ecord **S**eparator)
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* The separator used to distinguish records from one another.
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* Defaults to `"\n"`.
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`RS == ??` | Description
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---------------------- | -------------------------------------
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`"\n"` | Records are separated by the newline character. This is the default.
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*any single character* | Records are separated by each occurrence of the character. Multiple successive occurrences delimit empty records.
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`""` | Records are separated by runs of blank lines. Leading/trailing newlines in a file are ignored. If `FS` is a single character, then `"\n"` also serves as a field separator.
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*regexp* | Records are separated by occurrences of characters that match *regexp*. Leading/trailing matches delimit empty records.
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%%ANKI
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Cloze
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The {`RS`} variable is used to change the {record separator}.
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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: 1707310981382-->
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END%%
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%%ANKI
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Basic
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What is the default value of `RS`?
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Back: `"\n"`
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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: 1707310981380-->
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END%%
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%%ANKI
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Cloze
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If `RS` is a string with {more than one character}, it is treated as a {regexp}.
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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: 1707310981384-->
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END%%
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%%ANKI
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Basic
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What value of `RS` may `gawk` not process correctly?
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@ -131,11 +148,31 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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<!--ID: 1707310981394-->
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END%%
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%%ANKI
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Basic
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How is `RS = ""` interpreted?
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Back: `""` indicates runs of newlines should be treated as the record separator.
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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: 1707829409163-->
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END%%
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%%ANKI
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Basic
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What distinguishes `RS` value `""` and `\n\n+`?
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Back: When set to the former, `awk` strips leading/trailing newlines from the file.
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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: 1707829409170-->
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END%%
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%%ANKI
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Cloze
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If `RS = ""` and `FS` is set to {a single character}, the {newline character} *always* acts as a field separator.
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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: 1707829509362-->
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END%%
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* `NF` (**N**umber of **F**ields)
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* The 1-indexed number of fields found in the current record.
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* `FS` (**F**ield **S**eparator)
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* The separator used to distinguish fields from one another.
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* Defaults to `" "` which is a special character for **runs** of spaces, tabs, and newlines.
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%%ANKI
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Basic
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@ -168,6 +205,33 @@ Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 202
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<!--ID: 1707405259930-->
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END%%
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%%ANKI
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Basic
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What does incrementing `NF` do?
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Back: Creates the field and rebuilds the record.
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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: 1707829863717-->
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END%%
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%%ANKI
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Basic
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What does decrementing `NF` do?
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Back: Throws away fields and rebuilds the record.
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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: 1707829863726-->
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END%%
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* `FS` (**F**ield **S**eparator)
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* The separator used to distinguish fields from one another.
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`FS == ??` | Description
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---------------------------- | -------------------------------------
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`" "` | Fields are separated by runs of whitespace. Leading/trailing whitespace is ignored. This is the default.
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*any other single character* | Fields are separated by each occurrence of the character. Multiple successive occurrences delimit empty fields, as do leading/trailing occurrences.
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`"\n"` | Specific instance of the above row. It is used to treat the record as a single field (assuming newlines separate records).
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*regexp* | Fields are separated by occurrences of characters that match *regexp*. Leading/trailing matches delimit empty fields.
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`""` | Each individual character in the record becomes a separate field.
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%%ANKI
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Cloze
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The {`FS`} variable is used to change the {field separator}.
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@ -208,7 +272,7 @@ END%%
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%%ANKI
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Basic
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What distinguishes `FS` value `" "` and `[ \t\n]+`?
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Back: When set to the former, `awk` strips leading and trailing whitespace from each record.
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Back: When set to the former, `awk` strips leading/trailing whitespace from each record.
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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: 1707618833558-->
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END%%
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@ -222,7 +286,7 @@ END%%
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%%ANKI
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Cloze
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Setting `FS` to {`"\n"`} treats the {record as the single field}.
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If `RS` has its default value, setting `FS` to {`"\n"`} treats the {record as the single 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: 1707756447067-->
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END%%
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@ -230,7 +294,7 @@ END%%
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%%ANKI
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Basic
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What value of `FS` ensures `$1 = $0`?
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Back: `"\n"`
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Back: `RS`
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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: 1707756447069-->
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END%%
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<!--ID: 1707756447071-->
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END%%
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* `OFS` (**O**utput **F**ield **S**eparator)
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* Specifies the field separator used on printing.
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%%ANKI
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Cloze
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The {`OFS`} variable is used to change the {output field separator}.
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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: 1707829783790-->
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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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