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'def title BASH is weird
'def desc Interesting quirks of BASH
# {title}
{pagenav 4 min;01 May 2023;02 May 2023}
For very basic stuff, BASH is decently simple and intuitive, for example variables are set with the format {` name=value} and they're referenced with {` $name} {fn Of course this is just one of the many ways to reference and work with variables.}.
However, that changes once you start diving deeper (as I had to do for my {url Linuxgraphy by Strabo;/talks/linuxgraphy-by-strabo} presentation).
An example which illustrates my point would be:
```bash
'emplace
myvar=($(echo A B C))
myvar=1234
echo $((myvar += 46)) ${myvar[${myvar:0:1}]}
'endemplace
It has 3 things which really bothered me:
:ordered
1. The output of {` $(echo A B C)} is replaced "literally", and then the whole expression is evaluated.
Meaning, {` myvar=($(echo A B C))} turns into {` myvar=(A B C)}, which creates an array with those three letters.
I thought the "returned" value of {` $(echo A B C)} would be the whole string "A B C", so the array would have one element, that string.
However, {` $()} isn't really a function, which takes arguments, "creates" commands and returns their output.
It's {url Command {b Substitution};https://www.gnu.org/software/bash/manual/html_node/Command-Substitution.html}, the text gets executed and it's output {b replaces} the {` $(...)} itself (slightly reminiscent of {url LISP macros;https://lispcookbook.github.io/cl-cookbook/macros.html}).
Side note: obviously, the original expected behaviour can happen if we use some quotes:
```bash
myvar=("$(echo A B C)")
2. On the second line, {` myvar} {i becomes} an integer and then we do an arithmetic operation on it, nothing wrong here.
{` $\{parameter:offset:length\}} returns the substring from {` parameter} from {` offset} with size {` length}, but we're giving it a "number", so it should either throw some sort of error or return something default, like 0.
However it correctly returns the number 1 (and no, that isn't a default, the number is correctly parsed as a string).
This shows that numbers are actually strings too, and numerical operations are just weird string operations.
Contrary to any dynamically-typed language, it's not like the type of a variable is inferred from it's value, {url there isn't a type at all;https://tldp.org/LDP/abs/html/untyped.html}!
Which makes everything even more weird, considering you {i can} {url create variables with a specific type;https://www.gnu.org/software/bash/manual/bash.html#index-declare}.
3. Finally, the arguably biggest weirdness of it all, is {` $\{myvar[1]\}}.
It doesn't matter how it is represented, at first {` myvar} was the list of values A, B, C and now it's a number, this should return nothing.
Per contra, the value {` B} is returned instead!
Via trial and error, we find that our number will be returned when the index is 0, and with index 2 we get {` C}.
So all variables are arrays, and by default for integer and string operations, the first value is used?
This is strange, but it cannot be the full picture, because {url names have attributes;https://linux.die.net/Bash-Beginners-Guide/sect_10_01.html}, alongside it's type, a variable (name) can be read-only, but also have the "trace" flag, which only works with functions.
So, variables and functions are the same "object"?
Unfortunately, I couldn't find any definitive information on the topic, so this train of thought will have to be left unresolved.
And this is just one example, more bizarreness can be found with {url square brackets;https://www.vidarholen.net/contents/blog/?p=25} and {url most ok looking code;https://mywiki.wooledge.org/BashPitfalls}.
{url Some people;https://chrisdone.com/posts/shell-conduit/} even go as far to say:
.quote
Its syntax is insane, incredibly error prone, its defaults are awful, and it’s not a real big person programming language.
But I believe that is a step too far, {url there are benefits, especially when approaching it seriously;http://www.binaryphile.com/bash/2018/07/26/approach-bash-like-a-developer-part-1-intro.html}.
Every language has mind-numbing oddities, some get the out of the way from the start (like BASH), and others much later.
{footnotes}
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