59 lines
2.5 KiB
Markdown
59 lines
2.5 KiB
Markdown
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---
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title: Measuring Command Robustness
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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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- 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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> A self-contained shell script is more reliable because there are no other files to misplace.
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%%ANKI
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Basic
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What is a self-contained shell script?
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Back: A shell script that does not rely on the presence of other files.
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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: 1706726911473-->
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END%%
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%%ANKI
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Basic
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What makes a self-contained shell script more reliable?
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Back: There are no other files to misplace.
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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: 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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```bash
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$ awk 'program' input-file1 input-file2 ...
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$ awk -f program-file input-file1 input-file2 ...
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```
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It's interesting to think what else can be used as a measure of a command's robustness:
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* Required environment variables or environment variables formatted in a certain way
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* `$PATH` needs to point to a specific location
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* Whether the invoked program is present by default in a distribution or must be installed
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* The ability to run with or without an associated TTY
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* The ability to run with or without associated standard streams
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* `stdout`, `stderr`, `stdin`
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* How backwards compatible the invoked program is
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* Version mismatch may silently cause the same invocation to fail
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* Expected permissions
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* EUID, read permissions on an input file, etc.
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* Determinism of the program itself
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* Does output rely entirely on input or can it make nondeterministic choices
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* The amount of resources dedicated to the program
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* Failure may occur if not enough memory is provided to the command
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* Whether a program acts idempotently
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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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[^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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