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Bash 5.0 released

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Re: Bash 5.0 released

#201

Post by pwg »

chrisshroba wrote: post #59
nerdponx wrote: post #48

What is the value in creating built-in replacements for binaries like rm and stat?

It seems like this would eliminate the need to read a file from disk and fork a new process, both of which take time. If you're just removing a single file, this is probably negligible, but if you have a script iterating over 10k files, i.e., this speed-up may be more welcome.

True, but if you are iterating over 10k files and removing them, then a find|xargs pipe with xargs feeding rm the maximum number of parameters the kernel allows per fork will likely be faster than a bash interpreter loop, even with a bash builtin rm.

Re: Bash 5.0 released

#202

Post by Crestwave »

LukeShu wrote: post #38
BurritoAlPastor wrote: post #21

I can’t imagine what BASH_ARGV0 is for. Can someone more sage supply an example of what problem it solves?

A use-case I've long wanted it for is better "--help" messages. If you want to tell the user how to invoke the program again, argv[0] is the right thing: Given: #include int main(int argc, char *argv[]) { printf("Usage: %s [OPTIONS]\n", argv[0]); return 0; } Running it as `./dir/demo --help` gives: Usage: ./dir/demo [OPTIONS] Put it somewhere in $PATH, and run it as `demo --help`, and it will give: Usage: demo [OPTIO…

According to the email, it expands to $0, though. So as far as I can see, its only use is to set $0.

Re: Bash 5.0 released

#203

Post by jenscow »

fxfan wrote: post #31

As someone who lives in zsh and bash for interactive usage- I want to say- please do not write scripts in bash or zsh. Use powershell- its an amazingly well designed scripting language. Also- there is ammonite. Written for scripting.

I'm writing a powershell script at the moment. Why did I chose it? I didn't - it's the only thing guaranteed to be on Windows (realistically).

The problem with powershell as a scripting language, is it's designed to also be used as a shell. Which means, literals can be strings, function parameters are not separated, etc. It reminds me of Tcl in the 90s.

I really like what the powershell environment provides (like cmdlets, .NET) - but the language itself is dismal.

I would have preferred to have seen an existing scripting language, with .NET bindings added to it... the "NIH syndrome".

Re: Bash 5.0 released

#204

Post by klibertp »

nothrabannosir wrote: post #154
wlib wrote: post #11

Why did we keep the language of the shell and the OS separate? It seems like a needless abstraction which creates more harm than good (read a shell script vs any other language). While I'm at it, why is the filesystem and syscall api not just part of a standard userland language? For example, the filesystem could be exposed like an object tree rather than some syscall ritual. The syscalls could just be invisible, whe…

(re: Bash-vs-OS integration) bash is a programming language like any other, and you could use anything with a REPL as your shell. Python should do. In fact, I'll try it right now.. Yes, it works. Just sudo chsh -s /usr/bin/python and off you go. Once you start doing this for a bit, you'll notice that the Python REPL is an incredibly poor UI for repeated execution of subprocesses. It is very elaborate. Having to const…

> Python REPL is an incredibly poor UI for repeated execution of subprocesses

Python REPL, even with recent additions of TAB completion, is a poor REPL, period.

IPython, on the other hand, offers a much better programming environment than shell while still allowing easy access to most of the things you mention. Example:

    In [1]: from pathlib import Path
    In [2]: file = Path("~/.sbclrc").expanduser().read_text()
    In [3]: !echo "$file" | awk '!/^;;/'   # EDIT: to clarify, this shows passing
                                           # Python variable to a shell pipeline.

    #-quicklisp
    (let ((quicklisp-init (merge-pathnames quicklisp/setup.lisp
                                           (user-homedir-pathname))))
      (when (probe-file quicklisp-init)
        (load quicklisp-init)))
All things considered, between !, %, %% and /, IPython is a decent shell. I was using it for a few years as my main shell, actually - its QT Console implementation specifically. I was working on Windows back then, PowerShell didn't exist yet, and `cmd.exe` was... well, exactly the same as today.

TLDR: a shell is just a REPL with a few conveniences for specific tasks. Re-implement these and suddenly any REPL becomes a workable shell.

Re: Bash 5.0 released

#205

Post by JohnBooty »

aryamaan wrote: post #195
charlesdaniels wrote: post #29

Earlier quoted context omitted.

If you're doing it right, you are solving very different problems with shell vs any other language. Shell is best used as a tool for orchestrating other programs, you should not be implementing your programs in shell. Syscalls, in general, are used in lieu of objects or other abstractions because they more accurate mirror what the underlying hardware is doing. This isn't always the case, some syscalls are maintained…

> you should not be implementing your programs in shell. What should one be using instead in the current scenario? Python, Rust, Golang?

I think parent means (generally speaking) not to implement larger programs in shell.

If the tasks performed by your program can be expressed maintainably and performantly in shell, go for it.

For programs one size up, something like Perl or Ruby or any other language that allows easy execution of shell commands can be a great solution.

Of course, this all depends on any number of variables. Team competencies, target environments, etc. And with some effort even larger bash scripts can be kept maintainable-ish, and in some target environments (can't always count on other languages being available!) shell scripts might be the only available programming environment.

Re: Bash 5.0 released

#206

Post by pbhjpbhj »

zx2c4 wrote: post #113
a012 wrote: post #93

Earlier quoted context omitted.

Some application still requires bash, like wireguard

WireGuard doesn't require bash. The main configuration utility, wg(8), is written in vanilla C. However, the tools ship with a little convenience script, called wg-quick(8), which is indeed written in bash. It started out as the thing I was using to configure my laptop on the go, but then others found it helpful. It's by no means essential or central to WireGuard, and lots of people use different things to wrap wg(8)…

Totally aside: is there a tool that can parse a programs code, then consume a folder of (headers for?) versions of a dependency and say the versions that are [a priori] compatible?

Re: Bash 5.0 released

#207

Post by Tepix »

shpx wrote: post #69
giancarlostoro wrote: post #2

Any recommended reading for Bash? I'm somewhat new to it and it's interesting ways of getting things done. I've used it minimally in the past, but have found myself writing a 100> LOC script, which I can't help but feel I'm likely over-complicating certain bits and pieces.

I recommend reading and memorizing all 30-ish of the readline shortcuts https://tiswww.case.edu/php/chet/readline/readline.html#SEC1... Readline is the library bash uses for editing the input line, and it has some nice movement keys. For example Alt-b moves the cursor back a word, Ctrl-u deletes to the beginning of the line, Ctrl-w removes one word behind the cursor. They work in a bunch of other programs, like the P…

Excellent advice! Thanks.

Re: Bash 5.0 released

#208

Post by TheGrassyKnoll »

int_19h wrote: post #111
kawsper wrote: post #16

Earlier quoted context omitted.

That's true, so many times I have used shellcheck and started to improve a bash script, only to realize my time was better spent rewriting the script in Ruby.

Take a look at this, as well: https://amoffat.github.io/sh/

See also: http://www.pyinvoke.org/

Re: Bash 5.0 released

#209

Post by palunon »

hkt wrote: post #197
_kst_ wrote: post #84

With this release, bash now has three built-in variables (um, I mean "parameters") whose values are updated every time they're read: $RANDOM yields a random integer in the range 0..32767. (This feature was already there.) $EPOCHSECONDS yields the whole number of seconds since the epoch. $EPOCHREALTIME yields the number of seconds since the epoch with microsecond precision. I'm thinking of a new shell feature that wou…

Syntactic sugar is a phrase permanently marred for me by the ruby community: it means "cognitive load for other people who know the language but don't keep up with the faddy bits". It made me tremendously sad.

Yeah, but C-style "for" loops are nice, right ? Still, they really are a syntactic sugar for a "while".

The problem is more with a language having fady bits and people using them when they don't make the code clearer, than with syntactic sugar.

Re: Bash 5.0 released

#210

Post by klibertp »

laurent123456 wrote: post #182
int_19h wrote: post #118

Earlier quoted context omitted.

> I can write my code in bash and forget about it. In practice, this approach often results in code that works only on Linux, or on Linux and macOS. I especially hate it when people shove #!/bin/bash as a shebang, and doubly so when it's in scripts that are a part of some npm package. (On BSDs, Bash is not installed out of the box, and when it is installed, it's not in /bin, since it's not in the base system.) Still,…

"#!/usr/bin/env bash" is the right way to do it, but "#!/bin/bash" is so common that I'd just symlink it there if it's not already present. Any reason why these OSes don't do it automatically?

For FreeBSD, for example, `/usr/bin` is reserved for core system binaries only; whatever is installed from ports ends up in `/usr/local/bin`, and the shell bundled with the system is tcsh, not bash.
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