better loading
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---
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Title: Bash Arrays
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Subtitle: sub
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Desc: Brief intro to Bash Arrays
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Date: 2023-09-29
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Keywords: bash
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technology
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Category: Test
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Featured: True
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Public: True
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---
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**NOTE**
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This is a stolen article from [opensource.com](https://opensource.com/article/18/5/you-dont-know-bash-intro-bash-arrays)
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about bash scripting. It's a good article and I've decided to use it to test my
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markdown rendering.
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# Bash scripting
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[TOC]
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## Wait, but why?
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Writing about Bash is challenging because it's remarkably easy for an article
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to devolve into a manual that focuses on syntax oddities. Rest assured,
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however, the intent of this article is to avoid having you RTFM.
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## A real (actually useful) example
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To that end, let's consider a real-world scenario and how Bash can help:
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You are leading a new effort at your company to evaluate and optimize the
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runtime of your internal data pipeline. As a first step, you want to do a
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parameter sweep to evaluate how well the pipeline makes use of threads. For
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the sake of simplicity, we'll treat the pipeline as a compiled C++ black box
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where the only parameter we can tweak is the number of threads reserved for
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data processing: `./pipeline --threads 4.`
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## The basics
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The first thing we'll do is define an array containing the values of the
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`--threads` parameter that we want to test:
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```bash
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allThreads=(1 2 4 8 16 32 64 128)
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```
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In this example, all the elements are numbers, but it need not be the
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case—arrays in Bash can contain both numbers and strings, e.g., `myArray=(1
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2 "three" 4 "five")` is a valid expression. And just as with any other Bash
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variable, make sure to leave no spaces around the equal sign. Otherwise,
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Bash will treat the variable name as a program to execute, and the `=` as its
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first parameter!
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Now that we've initialized the array, let's retrieve a few of its
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elements. You'll notice that simply doing `echo $allThreads` will output only
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the first element.
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To understand why that is, let's take a step back and revisit how we usually
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output variables in Bash. Consider the following scenario:
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```bash
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type="article" echo "Found 42 $type"
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```
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Say the variable $type is given to us as a singular noun and we want to add
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an `s` at the end of our sentence. We can't simply add an s to `$type` since
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that would turn it into a different variable, `$types`. And although we could
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utilize code contortions such as `echo "Found 42 "$type"s"`, the best way
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to solve this problem is to use curly braces: `echo "Found 42 ${type}s"`,
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which allows us to tell Bash where the name of a variable starts and ends
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(interestingly, this is the same syntax used in JavaScript/ES6 to inject
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variables and expressions in template literals).
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So as it turns out, although Bash variables don't generally require curly
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brackets, they are required for arrays. In turn, this allows us to specify
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the index to access, e.g., `echo ${allThreads[1]}` returns the second element
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of the array. Not including brackets, e.g.,`echo $allThreads[1]`, leads Bash
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to treat `[1]` as a string and output it as such.
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Yes, Bash arrays have odd syntax, but at least they are zero-indexed, unlike
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some other languages (I'm looking at you, R).[^1]
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## Looping through arrays
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Although in the examples above we used integer indices in our arrays, let's
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consider two occasions when that won't be the case: First, if we wanted the
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$i-th element of the array, where $i is a variable containing the index of
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interest, we can retrieve that element using: echo ${allThreads[$i]}. Second,
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to output all the elements of an array, we replace the numeric index with
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the @ symbol (you can think of @ as standing for all):
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```bash
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type="article"
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echo "Found 42 $type"
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```
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*[RTFM]: Read the Fucking Manual
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*[HTML]: Hyper Text Markup Language
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[^1]: Example Footnote
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@ -1,86 +1,102 @@
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---
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Title: test
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Title: Bash Arrays
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Subtitle: sub
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Desc: brief desc
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Date: 2023-09-27
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Keywords: main
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foo
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bar
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qux
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Desc: Brief intro to Bash Arrays
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Date: 2023-09-29
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Keywords: bash
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technology
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Category: Test
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Featured: True
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Public: True
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---
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# Test article
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----------------------------------------
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This is a crazy testy
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**NOTE**
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This is a stolen article from [opensource.com](https://opensource.com/article/18/5/you-dont-know-bash-intro-bash-arrays)
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about bash scripting. It's a good article and I've decided to use it to test my
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markdown rendering.
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# Bash scripting
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### toc?
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[TOC]
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## foo
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HTML
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## Wait, but why?
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lipsum[^1]
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Writing about Bash is challenging because it's remarkably easy for an article
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to devolve into a manual that focuses on syntax oddities. Rest assured,
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however, the intent of this article is to avoid having you RTFM.
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<div>INLINE DIV<b>bold</b></div>
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## A real (actually useful) example
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### bar bar
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To that end, let's consider a real-world scenario and how Bash can help:
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You are leading a new effort at your company to evaluate and optimize the
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runtime of your internal data pipeline. As a first step, you want to do a
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parameter sweep to evaluate how well the pipeline makes use of threads. For
|
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the sake of simplicity, we'll treat the pipeline as a compiled C++ black box
|
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where the only parameter we can tweak is the number of threads reserved for
|
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data processing: `./pipeline --threads 4.`
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| important | table |
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|-----------|-------|
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| value | 2 |
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| 3 | 4 |
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| 5 | 2 |
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## The basics
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## foo
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The first thing we'll do is define an array containing the values of the
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`--threads` parameter that we want to test:
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#### big code
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```py
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from django.db import models
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from django.utils.translation import gettext as _
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from start.models import Searchable
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import logging
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logger = logging.getLogger(__name__)
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import markdown
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ARTICLE_DIR = "/app/blog/data/articles"
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EXTENSIONS = [
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"extra",
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"admonition",
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"codehilite",
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"toc"
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]
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class Category(models.Model):
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"""
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A category of blog posts
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Name not translated because it would make i18n in urls and Searchables specifically a pain.
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Maybe some day it would be cool if these were Searchable
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"""
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name= models.CharField(max_length=50)
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slug = models.SlugField()
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class Meta:
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verbose_name = _("Category")
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verbose_name_plural = _("Categories")
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def __str__(self):
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return f"{{<{self.__class__.__name__}>\"{self.name}\"}}"
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```bash
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allThreads=(1 2 4 8 16 32 64 128)
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```
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### a
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bar
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#### a
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qux
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###### a
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baau
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In this example, all the elements are numbers, but it need not be the
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case—arrays in Bash can contain both numbers and strings, e.g., `myArray=(1
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2 "three" 4 "five")` is a valid expression. And just as with any other Bash
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variable, make sure to leave no spaces around the equal sign. Otherwise,
|
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Bash will treat the variable name as a program to execute, and the `=` as its
|
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first parameter!
|
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|
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Now that we've initialized the array, let's retrieve a few of its
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elements. You'll notice that simply doing `echo $allThreads` will output only
|
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the first element.
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|
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To understand why that is, let's take a step back and revisit how we usually
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output variables in Bash. Consider the following scenario:
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|
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```bash
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type="article" echo "Found 42 $type"
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```
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Say the variable $type is given to us as a singular noun and we want to add
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an `s` at the end of our sentence. We can't simply add an s to `$type` since
|
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that would turn it into a different variable, `$types`. And although we could
|
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utilize code contortions such as `echo "Found 42 "$type"s"`, the best way
|
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to solve this problem is to use curly braces: `echo "Found 42 ${type}s"`,
|
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which allows us to tell Bash where the name of a variable starts and ends
|
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(interestingly, this is the same syntax used in JavaScript/ES6 to inject
|
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variables and expressions in template literals).
|
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|
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So as it turns out, although Bash variables don't generally require curly
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brackets, they are required for arrays. In turn, this allows us to specify
|
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the index to access, e.g., `echo ${allThreads[1]}` returns the second element
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of the array. Not including brackets, e.g.,`echo $allThreads[1]`, leads Bash
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to treat `[1]` as a string and output it as such.
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|
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Yes, Bash arrays have odd syntax, but at least they are zero-indexed, unlike
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some other languages (I'm looking at you, R).[^1]
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|
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## Looping through arrays
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Although in the examples above we used integer indices in our arrays, let's
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consider two occasions when that won't be the case: First, if we wanted the
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$i-th element of the array, where $i is a variable containing the index of
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interest, we can retrieve that element using: echo ${allThreads[$i]}. Second,
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to output all the elements of an array, we replace the numeric index with
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the @ symbol (you can think of @ as standing for all):
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|
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```bash
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type="article"
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echo "Found 42 $type"
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```
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*[RTFM]: Read the Fucking Manual
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*[HTML]: Hyper Text Markup Language
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[^1]: foooootnote
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[^1]: Example Footnote
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|
|
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|||
|
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@ -74,7 +74,7 @@ class BlogPost(Searchable):
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"""
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logger.info(f"regenerating article from markdown for: {self}")
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try:
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f_en = open(f"{ARTICLE_DIR}/en-{self.slug}.md")
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with open(f"{ARTICLE_DIR}/en-{self.slug}.md") as f_en:
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body_en: str = f_en.read()
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@ -95,6 +95,7 @@ class BlogPost(Searchable):
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except Exception as e:
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logger.warning(f"could not generate metadata {self.slug} from markdown: {e}")
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self.body_en = ""
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self.body_en = html_en
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except FileNotFoundError as e:
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# TODO: mark as untranslated
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@ -102,7 +103,7 @@ class BlogPost(Searchable):
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except Exception as e:
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logger.warning(f"could not generate article {self.slug} from markdown: {e}")
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try:
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f_de = open(f"{ARTICLE_DIR}/de-{self.slug}.md")
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with open(f"{ARTICLE_DIR}/de-{self.slug}.md") as f_de:
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body_de: str = f_de.read()
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@ -123,6 +124,7 @@ class BlogPost(Searchable):
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except Exception as e:
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logger.warning(f"could not generate metadata {self.slug} from markdown: {e}")
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self.body_de = ""
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self.body_de = html_de
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except FileNotFoundError as e:
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# TODO: mark as untranslated
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