blog-markdown #31
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@ -0,0 +1,102 @@
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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
|
||||
to devolve into a manual that focuses on syntax oddities. Rest assured,
|
||||
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
|
||||
runtime of your internal data pipeline. As a first step, you want to do a
|
||||
parameter sweep to evaluate how well the pipeline makes use of threads. For
|
||||
the sake of simplicity, we'll treat the pipeline as a compiled C++ black box
|
||||
where the only parameter we can tweak is the number of threads reserved for
|
||||
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
|
||||
case—arrays in Bash can contain both numbers and strings, e.g., `myArray=(1
|
||||
2 "three" 4 "five")` is a valid expression. And just as with any other Bash
|
||||
variable, make sure to leave no spaces around the equal sign. Otherwise,
|
||||
Bash will treat the variable name as a program to execute, and the `=` as its
|
||||
first parameter!
|
||||
|
||||
Now that we've initialized the array, let's retrieve a few of its
|
||||
elements. You'll notice that simply doing `echo $allThreads` will output only
|
||||
the first element.
|
||||
|
||||
To understand why that is, let's take a step back and revisit how we usually
|
||||
output variables in Bash. Consider the following scenario:
|
||||
|
||||
```bash
|
||||
type="article" echo "Found 42 $type"
|
||||
```
|
||||
|
||||
Say the variable $type is given to us as a singular noun and we want to add
|
||||
an `s` at the end of our sentence. We can't simply add an s to `$type` since
|
||||
that would turn it into a different variable, `$types`. And although we could
|
||||
utilize code contortions such as `echo "Found 42 "$type"s"`, the best way
|
||||
to solve this problem is to use curly braces: `echo "Found 42 ${type}s"`,
|
||||
which allows us to tell Bash where the name of a variable starts and ends
|
||||
(interestingly, this is the same syntax used in JavaScript/ES6 to inject
|
||||
variables and expressions in template literals).
|
||||
|
||||
So as it turns out, although Bash variables don't generally require curly
|
||||
brackets, they are required for arrays. In turn, this allows us to specify
|
||||
the index to access, e.g., `echo ${allThreads[1]}` returns the second element
|
||||
of the array. Not including brackets, e.g.,`echo $allThreads[1]`, leads Bash
|
||||
to treat `[1]` as a string and output it as such.
|
||||
|
||||
Yes, Bash arrays have odd syntax, but at least they are zero-indexed, unlike
|
||||
some other languages (I'm looking at you, R).[^1]
|
||||
|
||||
## Looping through arrays
|
||||
|
||||
Although in the examples above we used integer indices in our arrays, let's
|
||||
consider two occasions when that won't be the case: First, if we wanted the
|
||||
$i-th element of the array, where $i is a variable containing the index of
|
||||
interest, we can retrieve that element using: echo ${allThreads[$i]}. Second,
|
||||
to output all the elements of an array, we replace the numeric index with
|
||||
the @ symbol (you can think of @ as standing for all):
|
||||
|
||||
```bash
|
||||
type="article"
|
||||
echo "Found 42 $type"
|
||||
```
|
||||
|
||||
*[RTFM]: Read the Fucking Manual
|
||||
*[HTML]: Hyper Text Markup Language
|
||||
|
||||
[^1]: Example Footnote
|
||||
|
|
@ -1,86 +1,102 @@
|
|||
---
|
||||
Title: test
|
||||
Title: Bash Arrays
|
||||
Subtitle: sub
|
||||
Desc: brief desc
|
||||
Date: 2023-09-27
|
||||
Keywords: main
|
||||
foo
|
||||
bar
|
||||
qux
|
||||
Desc: Brief intro to Bash Arrays
|
||||
Date: 2023-09-29
|
||||
Keywords: bash
|
||||
technology
|
||||
Category: Test
|
||||
Featured: True
|
||||
Public: True
|
||||
---
|
||||
|
||||
# Test article
|
||||
----------------------------------------
|
||||
This is a crazy testy
|
||||
**NOTE**
|
||||
|
||||
This is a stolen article from [opensource.com](https://opensource.com/article/18/5/you-dont-know-bash-intro-bash-arrays)
|
||||
about bash scripting. It's a good article and I've decided to use it to test my
|
||||
markdown rendering.
|
||||
|
||||
# Bash scripting
|
||||
|
||||
### toc?
|
||||
[TOC]
|
||||
|
||||
## foo
|
||||
|
||||
HTML
|
||||
## Wait, but why?
|
||||
|
||||
lipsum[^1]
|
||||
Writing about Bash is challenging because it's remarkably easy for an article
|
||||
to devolve into a manual that focuses on syntax oddities. Rest assured,
|
||||
however, the intent of this article is to avoid having you RTFM.
|
||||
|
||||
<div>INLINE DIV<b>bold</b></div>
|
||||
## A real (actually useful) example
|
||||
|
||||
### bar bar
|
||||
To that end, let's consider a real-world scenario and how Bash can help:
|
||||
You are leading a new effort at your company to evaluate and optimize the
|
||||
runtime of your internal data pipeline. As a first step, you want to do a
|
||||
parameter sweep to evaluate how well the pipeline makes use of threads. For
|
||||
the sake of simplicity, we'll treat the pipeline as a compiled C++ black box
|
||||
where the only parameter we can tweak is the number of threads reserved for
|
||||
data processing: `./pipeline --threads 4.`
|
||||
|
||||
| important | table |
|
||||
|-----------|-------|
|
||||
| value | 2 |
|
||||
| 3 | 4 |
|
||||
| 5 | 2 |
|
||||
## The basics
|
||||
|
||||
## foo
|
||||
The first thing we'll do is define an array containing the values of the
|
||||
`--threads` parameter that we want to test:
|
||||
|
||||
#### big code
|
||||
|
||||
```py
|
||||
from django.db import models
|
||||
from django.utils.translation import gettext as _
|
||||
from start.models import Searchable
|
||||
|
||||
import logging
|
||||
logger = logging.getLogger(__name__)
|
||||
|
||||
import markdown
|
||||
ARTICLE_DIR = "/app/blog/data/articles"
|
||||
EXTENSIONS = [
|
||||
"extra",
|
||||
"admonition",
|
||||
"codehilite",
|
||||
"toc"
|
||||
]
|
||||
|
||||
class Category(models.Model):
|
||||
"""
|
||||
A category of blog posts
|
||||
|
||||
Name not translated because it would make i18n in urls and Searchables specifically a pain.
|
||||
Maybe some day it would be cool if these were Searchable
|
||||
"""
|
||||
name= models.CharField(max_length=50)
|
||||
slug = models.SlugField()
|
||||
|
||||
class Meta:
|
||||
verbose_name = _("Category")
|
||||
verbose_name_plural = _("Categories")
|
||||
|
||||
def __str__(self):
|
||||
return f"{{<{self.__class__.__name__}>\"{self.name}\"}}"
|
||||
```bash
|
||||
allThreads=(1 2 4 8 16 32 64 128)
|
||||
```
|
||||
|
||||
### a
|
||||
bar
|
||||
#### a
|
||||
qux
|
||||
###### a
|
||||
baau
|
||||
In this example, all the elements are numbers, but it need not be the
|
||||
case—arrays in Bash can contain both numbers and strings, e.g., `myArray=(1
|
||||
2 "three" 4 "five")` is a valid expression. And just as with any other Bash
|
||||
variable, make sure to leave no spaces around the equal sign. Otherwise,
|
||||
Bash will treat the variable name as a program to execute, and the `=` as its
|
||||
first parameter!
|
||||
|
||||
Now that we've initialized the array, let's retrieve a few of its
|
||||
elements. You'll notice that simply doing `echo $allThreads` will output only
|
||||
the first element.
|
||||
|
||||
To understand why that is, let's take a step back and revisit how we usually
|
||||
output variables in Bash. Consider the following scenario:
|
||||
|
||||
```bash
|
||||
type="article" echo "Found 42 $type"
|
||||
```
|
||||
|
||||
Say the variable $type is given to us as a singular noun and we want to add
|
||||
an `s` at the end of our sentence. We can't simply add an s to `$type` since
|
||||
that would turn it into a different variable, `$types`. And although we could
|
||||
utilize code contortions such as `echo "Found 42 "$type"s"`, the best way
|
||||
to solve this problem is to use curly braces: `echo "Found 42 ${type}s"`,
|
||||
which allows us to tell Bash where the name of a variable starts and ends
|
||||
(interestingly, this is the same syntax used in JavaScript/ES6 to inject
|
||||
variables and expressions in template literals).
|
||||
|
||||
So as it turns out, although Bash variables don't generally require curly
|
||||
brackets, they are required for arrays. In turn, this allows us to specify
|
||||
the index to access, e.g., `echo ${allThreads[1]}` returns the second element
|
||||
of the array. Not including brackets, e.g.,`echo $allThreads[1]`, leads Bash
|
||||
to treat `[1]` as a string and output it as such.
|
||||
|
||||
Yes, Bash arrays have odd syntax, but at least they are zero-indexed, unlike
|
||||
some other languages (I'm looking at you, R).[^1]
|
||||
|
||||
## Looping through arrays
|
||||
|
||||
Although in the examples above we used integer indices in our arrays, let's
|
||||
consider two occasions when that won't be the case: First, if we wanted the
|
||||
$i-th element of the array, where $i is a variable containing the index of
|
||||
interest, we can retrieve that element using: echo ${allThreads[$i]}. Second,
|
||||
to output all the elements of an array, we replace the numeric index with
|
||||
the @ symbol (you can think of @ as standing for all):
|
||||
|
||||
```bash
|
||||
type="article"
|
||||
echo "Found 42 $type"
|
||||
```
|
||||
|
||||
*[RTFM]: Read the Fucking Manual
|
||||
*[HTML]: Hyper Text Markup Language
|
||||
|
||||
[^1]: foooootnote
|
||||
[^1]: Example Footnote
|
||||
|
|
|
|||
|
|
@ -74,7 +74,7 @@ class BlogPost(Searchable):
|
|||
"""
|
||||
logger.info(f"regenerating article from markdown for: {self}")
|
||||
try:
|
||||
f_en = open(f"{ARTICLE_DIR}/en-{self.slug}.md")
|
||||
with open(f"{ARTICLE_DIR}/en-{self.slug}.md") as f_en:
|
||||
|
||||
body_en: str = f_en.read()
|
||||
|
||||
|
|
@ -95,6 +95,7 @@ class BlogPost(Searchable):
|
|||
except Exception as e:
|
||||
logger.warning(f"could not generate metadata {self.slug} from markdown: {e}")
|
||||
|
||||
self.body_en = ""
|
||||
self.body_en = html_en
|
||||
except FileNotFoundError as e:
|
||||
# TODO: mark as untranslated
|
||||
|
|
@ -102,7 +103,7 @@ class BlogPost(Searchable):
|
|||
except Exception as e:
|
||||
logger.warning(f"could not generate article {self.slug} from markdown: {e}")
|
||||
try:
|
||||
f_de = open(f"{ARTICLE_DIR}/de-{self.slug}.md")
|
||||
with open(f"{ARTICLE_DIR}/de-{self.slug}.md") as f_de:
|
||||
|
||||
body_de: str = f_de.read()
|
||||
|
||||
|
|
@ -123,6 +124,7 @@ class BlogPost(Searchable):
|
|||
except Exception as e:
|
||||
logger.warning(f"could not generate metadata {self.slug} from markdown: {e}")
|
||||
|
||||
self.body_de = ""
|
||||
self.body_de = html_de
|
||||
except FileNotFoundError as e:
|
||||
# TODO: mark as untranslated
|
||||
|
|
|
|||
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