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Comment by augustk | Hacker News Reader

This article is not specifically about Bash, but about the shell command language sh. The POSIX Shell is a standardized subset of Bash which has even better portability. I would recommend learning and using sh unless you really need Bash.

https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V...

Your script will use sh if it starts with #!/bin/sh (instead of #!/bin/bash).

I can also recommend ShellCheck which is a shell script analysis tool (implemented in Haskell) which can find errors and potential problems in your scripts. On a Debian system, installing ShellScheck is as simple as `sudo apt install shellcheck'.

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>I would recommend learning and using sh unless you really need Bash.

I don't buy this argument. Ok, it's a standard, but sometimes it's a pain-in-the-hole standard. Bash augmentations lessen some of the pains, and it's just nicer. The only situation is if you're using busybox in a very limited system or you reeeeeally need your script to run on many difference unices, which let's be honest, is not that common nowadays.

All of this was covered in great detail in the 2000s, when Debian and Ubuntu switched /bin/sh to the Debian Almquist shell, which was basically POSIX-only with some 3 things that Debian people simply couldn't live without, and encouraged system scripts to use it. If you weren't around then, go and read the discussions. They're mostly still available, and they cover some important stuff that straw man counterarguments regularly miss.

The Debian people were concerned, for starters, with how much time the Bourne Again shell spent, at process initialization, setting up things for extensions and interactive features that were never employed in non-interactive "sh" mode; a significant cause for concern given how much of the system was executable shell scripts.

>with some 3 things that Debian people simply couldn't live without

Curious, what are the 3 things ?

But yes, people should always use sh (or ksh) for scripting as opposed to bash, why, it is far more portable to other systems.

Originally it was echo -n, local, and logical operators in test. There was just so much Debian stuff that assumed these.

* https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=294962

They've added 2 more since.

* https://www.debian.org/doc/debian-policy/ch-files.html#scrip...

Strictly speaking, there are other differences between the Debian Almquist shell and a truly SUS conformant sh.

* https://unix.stackexchange.com/q/697007/5132

But the aforementioned are what Debian people explicitly wanted and couldn't live without. Note that the StackExchange answer is a comparison of a 2022 dash to a 2017 standard, neither of which existed at the time. Debian Policy, the Debian Almquist shell, and the POSIX standard have all been revised since then.

> Bash augmentations lessen some of the pains, and it's just nicer

Both sh and bash are terrible, ugly hacks. Anything that requires more than 3 lines of them (including the #! line) should be written in a proper scripting language.

Though I do agree that cross-platformity to that level is rarely meaningful, and so things like python are just as likely available/can be made available.

Which version of python though?

Add a flake.nix file and you get completely reproducible program versions if you really want.

But I know that you meant it as a rhetoric, so my non-rhetorical answer would be that python3 is almost universally available on distros that are not minified deliberately (containers).

> python3 is almost universally available on distros that are not minified deliberately (containers)

Writing control scripts for use inside containers is currently my biggest application of BASH scripts. What makes BASH (or other shells) handy is the lack of supporting files that are needed - just copy in the script and you're ready to go.

I was going to say something similar. I try to avoid adding anything to my final images. Each extra dependency is something else to update, more surface areas for attacks, another thing to justify, etc. Much rather just use the slimmest base and the tools already available.

Which version of Bash?

The various sub-versions of bash are a lot more compatible than the sub-versions of python 3. Just today stuff was breaking on me because of differences between python 3.6 and 3.8

It depends on what features of BASH that you want to use. If you target v3 (as I usually do), then that or a newer version will likely be already installed. There's very little issue with backwards compatibility.

My system Python tree is almost 1GB. That doesn't matter for desktop systems, but most software is published as container images these days and using a language like Python, Ruby or Perl for an image that doesn't already need it is pretty wasteful and pulls in a lot of extra dependencies.

I'm not sure there is a good alternative to sh/bash shell scripts as most dynamic languages have become pretty large dependencies these days.

That surely includes plenty of globally installed dependencies. I looked at the package sizes for debian and it is around 100 kB for the python3 package and on the order of another 100kb for python3-minimal. Couldn’t find a cumulative install size, but it is surely not larger than a few megabytes.

Just span up a clean alpine linux container and installed python3, it added 51MB according to apk.

Arch does not do much spliting (except ruby where there is some kind of circular dependency)

Any way for: python - 75M perl - 59M ruby - 25M bash - 8M dash - 0.15M

Until someone decides to write something that's only available in X version of Python. While there are certainly v4 and v5 bash-isms, they are far and few between compared to most languages.

...that said, having to support bash 3.2 for MacOS is a horrible thing.

Python or lua scripts which are mainly clumsy and overly verbose wrappers around shell commands are way, way worse than shell scripts.

AWK is part of the POSIX standard and is therefore on every UNIX-like. People really need to remember AWK exists and is a real, proper scripting language with a very sane syntax (it's not just for cryptic one-liners, really!)

> is not that common nowadays

Due to docker, minimalistic Linux'es have been more common, including trimmed-down versions of distros that would otherwise feature bash.

bash is rarely the focus though, it really just costs 1MB in storage, which is nothing comparing to python,etc.

Nonetheless Bash is very frequently omitted in my experience.

Well, usually I have to decide between „do I look up the magic incantation to install bash in this container and risk fucking up the layer cache“ or „do I modify this script to not use bash-isms and feel like I’m a Unix purist in the process“, and the answer is the latter usually

Just 1MB? That's most of a double-density floppy disk!

I do small embedded systems with busybox, even that I can squeeze in bash when I need that, it's about 1MB in size and gives a lot more than busybox's sh. Another option is Lua which is also great.

If you wish require some users to install an interpreter, you might as well go for Korn or a real programming language. If you want to use something that's portable and installed everywhere, that's POSIX sh (or at most dash-like level). Bash is in the poor middle which isn't good enough for either side, unless you really know what's your target and don't care about elsewhere.

I usually target BASHv3 in my scripts, but then I know the environment that will be using those scripts. My biggest issue with POSIX is the use of the backtick which is difficult to read and parse.

ShellCheck is absolutely the most important thing to use when writing scripts. Each time that you get a warning that you don't recognise is a learning opportunity - just follow the link provided in the warning. Also, take the time to add the "# shellcheck disable=" comments so that scripts don't issue any warnings from shellcheck.

I also recommend visiting https://mywiki.wooledge.org/BashFAQ for avoiding the many footguns, especially with filename parsing.

> My biggest issue with POSIX is the use of the backtick which is difficult to read and parse.

POSIX also has $(command) for command substitution. It can certainly be annoying when it's not used, though. I think shellcheck will recommend it over backticks.

Thanks, I didn't know that, but then I almost never target POSIX. My next complaint would be the use of '[' as a test rather than my preferred '[['.

Edit: After looking for a problem with POSIX, I found this obscure issue that may well catch out people as under POSIX, IFS is a terminator rather than a separator: https://mywiki.wooledge.org/BashPitfalls#IFS.3D.2C_read_-ra_...

> My biggest issue with POSIX is the use of the backtick which is difficult to read and parse.

I always use $(...) or rather "$(...)" instead of backticks.

  Command substitution shall occur when the command is enclosed as follows:

    $(command)

  or (backquoted version):

    `command`

https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V...

> I would recommend learning and using sh unless you really need Bash.

Nah I like using bash features and all the systems that I care about have /bin/bash so it doesn't matter.

> The POSIX Shell is a standardized subset of Bash which has even better portability.

It would be much more correct to say that bash's features are a superset of the shell features standardised by the POSIX standard, as is the case for several other shells (each adding their own parts on top of the standard) too.

I recommend learning bash if you know that bash is available for all your targets, since bash brings many niceties that sh doesn't have.

Some may have different Bash versions installed though.

That's easy to check for. sh implementations can vary also.

Does the POSIX implementation vary for sh though? AFAIK some interpreters choose to add some extras (like `local`), but all of them at the very minimum must adhere to the POSIX spec from what I've understood.

There are a couple examples in this stack overflow answer:

https://stackoverflow.com/questions/11376975/is-there-a-mini...

> not specifically about Bash, but about the shell command language sh

or as I've taken to calling it, Ba + sh

macOS and plenty of popular Linux distributions symlink /bin/sh to /bin/bash. Some link it to /bin/dash. There may be different ones.

Meaning /bin/sh is not more portable because you can’t be sure which shell will be used.

Not only is it not more portable, POSIX doesn't even require that it exists at all.

    Applications should note that the standard PATH to the shell cannot be assumed to be either /bin/sh or /usr/bin/sh, and should be determined by interrogation of the PATH returned by getconf PATH, ensuring that the returned pathname is an absolute pathname and not a shell built-in.

I don't know how this trend started but now it's been cargo-culted to death. Same with the /usr/bin/env thing in shebangs.

One use-case for /bin/sh over /bin/bash these days is that the alpine docker image (base image for a lot of docker images) has /bin/sh but not /bin/bash

Bash is POSiX compatible.

ShellCheck can check for POSIX compliance with the option `--shell sh', e.g.

  shellcheck --shell sh myscript.sh

"If bash is invoked with the name sh, it tries to mimic the startup behavior of historical versions of sh as closely as possible, while conforming to the POSIX standard as well"

> This article is not specifically about Bash, but about the shell command language sh.

Exactly. The title is just plain wrong. Furthermore, TFA does not argue a "case", it simply tries to specify the language.

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