[derefr]

• The primary win for all of those utilities would be in separating their horribly-large arrays of top-level runtime switches into subcommands that each have a restricted, learnable set of runtime switches relevant only to that subcommand. (See: git, docker, lvm, ip, ufw).

• As well, for top-level switches that are really preferences—that is, switches that don't apply to a use-case, but rather to a user—read those from ~/.config/foo/foorc with defaults in /etc/foo/foorc. Don't expose them at all as runtime switches. If there are features that would be customized by different wrapper-client UIs, provide a --config-file=[file] switch that takes a config-file that sets those. And for special drivers, like Makefiles or CI setups, that have a matrix of different UI options they might want to ask for, you can provide FOO_OPTION env-vars. (See: curl, compiler toolchains, ffmpeg, apt). In ffmpeg's case, there are even config-file presets—basically little plug-ins of config options you can enable as a group. You can dump new files into the /etc/ffmpeg/presets or ~/.config/ffmpeg/presets to add them as presets.

• For switches that are exposed individually, but which are also aggregated into switch-group-setting switches, in most cases there's literally no use-case for setting the individual switches, only the switch-group-setting switch. Remove the individual switches. Just because the program could theoretically be configured to do X compatibility thing for old-arch Foo, but not Y other old compatibility thing for old-arch Foo (where any time you're talking to Foo you always need both), you don't have to expose both an X switch and a Y switch. Just expose a --foo-compat switch and be done with it. People trying to use your binary on other weird OSes shouldn't be doing so by combining tons of option-switches; they should sit down and port your program to that OS, by finding the place in your program where you've defined {arch -> shim flag set} mappings, adding a new mapping for their arch, and exposing it as a new external --bar-compat switch.

• Speaking of compat flags, try just making such behaviors always-on when you build targeting the relevant arch, rather than needing to specify them at runtime. The only real use-case for runtime compat switches is as an IPC/RPC client talking to a server that expects the weird behaviour. And even then, your client should first try to auto-detect the server's expectations, and you should only add the runtime switch if that auto-detection turns out to be unreliable. (Meanwhile, If you're the IPC/RPC server, the compat settings belong in the config file. See: Samba, NFS, Netatalk, ...)

• If your binary manipulates state (like, say, how git manipulates repos), and you change the way it does so in a backward-incompatible manner, you might be tempted to add a runtime switch to turn the old behaviour back on to allow collaboration with people using older versions. If your state-store is at all extensible, though, you should instead add a field for a schema-version and a flag for pinning the state-store to that schema-version, as well as a subcommand to pin/unpin a given state-store's schema-version. Now your binary will upgrade the schema of its state-store by default, but will respect "protected" state-stores and perform only backward-compatible operations on those. (Importantly, this guides the code architecture into failing by default instead of doing something backward-incompatible; whereas, with backcompat switches, you're always forcing a state-store schema-migration on people by default every time you add new code, unless/until you add a matching backcompat-switch.)

• quiet/verbose and interactive/batch are silly "mode switches" to have in modern programs, just like forking is a silly way to do daemons when you've got a modern init(8). Put interactively-useful information on stdout, and do interactive prompting, if-and-only-if isatty(STDIN); put information of all levels of usefulness on syslog with appropriate error-level tags attached. It's up to the thing running your program to provide a PTY or not, and to filter your output or not. Be friendly to expect(1).

These guidelines together should trim each subcommand to a reasonable "visible" option-set. Now just ensure that typing "man command subcommand" gets you a separate man-page written just for the subcommand, and add bash/zsh completion for each subcommand and for the subcommands list itself.

[Hello71]

> • The primary win for all of those utilities would be in separating their horribly-large arrays of top-level runtime switches into subcommands that each have a restricted, learnable set of runtime switches relevant only to that subcommand. (See: git, docker, lvm, ip, ufw).

In principle I agree. In practice, all of the commands you listed are multi-tool commands. For example, git overall can be described as a "content tracker"; only its subcommands can be described as doing one thing, and even then often they do multiple duties (to a newbie, git reset apparently does three different things). In contrast, two of the commands you listed (ps and rsync) do only one thing; list processes and copy files. The third, tar, does technically have multiple modes, but most of the switches apply to multiple modes (-f, compression settings, etc). How would you break these up into subcommands?

> • As well, for top-level switches that are really preferences—that is, switches that don't apply to a use-case, but rather to a user—read those from ~/.config/foo/foorc with defaults in /etc/foo/foorc. Don't expose them at all as runtime switches. If there are features that would be customized by different wrapper-client UIs, provide a --config-file=[file] switch that takes a config-file that sets those. And for special drivers, like Makefiles or CI setups, that have a matrix of different UI options they might want to ask for, you can provide FOO_OPTION env-vars. (See: curl, compiler toolchains, ffmpeg, apt). In ffmpeg's case, there are even config-file presets—basically little plug-ins of config options you can enable as a group. You can dump new files into the /etc/ffmpeg/presets or ~/.config/ffmpeg/presets to add them as presets.

Some would argue that this is an anti-pattern and that such configuration should reside in your shell as an alias or function. Regardless, with the possible exception of ps, for the commands you listed, which options exactly would you move into a configuration file? It would likely not be a good idea, for example, to say that all tar -c commands should imply -J, since that would break lots of scripts.

> • For options that are aggregated into option-set flags, where there's literally no use for the options outside of their use in the option-set flag, remove the individual options. Just because the program could theoretically be configured to do X compatibility thing for old-arch Foo, but not Y other old compatibility thing for old-arch Foo, you don't have to support both an X and Y option. Just expose a --foo-compat option and be done with it. People trying to use your binary on other weird OSes shouldn't be doing so by combining tons of option-switches; they should sit down and port your program to that OS, by finding the place in your program where you've defined {arch -> shim flag set} mappings, adding a new mapping for their arch, and exposing it as a new external --bar-compat switch.

I don't understand what this means. Can you give a concrete example?

> • Speaking of compat flags, try just making such behaviors always-on when you build targeting the relevant arch, rather than needing to specify them at runtime. The only real use-case for runtime compat switches is as an IPC/RPC client talking to a server that expects the weird behaviour. And even then, your client should first try to auto-detect the server's expectations, and you should only add the runtime switch if that auto-detection turns out to be unreliable. (Meanwhile, If you're the IPC/RPC server, the compat settings belong in the config file. See: Samba, NFS, Netatalk, ...)

Again, I don't understand what this means.

> Those four things together should trim each subcommand to a reasonable "visible" option-set. Now just ensure that typing "man command subcommand" gets you a separate man-page written just for the subcommand, and add bash/zsh completion for each subcommand and for the subcommands list itself.

I agree with this conclusion given the premises you provided, but the issue is that the premises themselves appear to be incorrect.

Broadly speaking, most complaints about the commands you listed originate in poor understanding of their interfaces; everybody thinks they're hard, so nobody ever reads the man page and learns how to use them correctly. For example, complaints about not knowing tar -z from -j are mostly a result of not knowing that GNU and at least one BSD tar know how to automatically select compression format in at least some cases. A similar situation is the cause of "ps -aux" and such monstrosities as "rsync -arlv -e ssh dir host:dir".

[derefr]

1. They commands I listed seem like "inherently multi-tool" commands because they've been refactored into multi-tool commands. ip is (mostly) a refactoring of ifconfig(1), but also of ethtool(1) and arp(1) and a few other things. A proper multi-mode refactoring of ps(1) would integrate overlapping utilities like pgrep(1) and fuser(1)/lsof(1), and then split those back down along separate lines.

A proper multi-subcommand refactoring of tar, I would think, might involve an interestingly different usage—a "fluent OOP interface" involving either a series, or pipeline, of invocations, all involving tar subcommands. For example:

   tar manifest create --new-root=/ . | tar archive assemble --extended-attributes --timestamps --compression=lzma > foo.tar.xz

or, equivalently:

   tar manifest create --new-root=/ . > foo.manifest
   tar archive new --extended-attributes --timestamps --compression=lzma > foo.tar.xz
   tar archive insert foo.tar.xz foo.manifest

then, later:

   tar manifest read foo.tar.xz | grep -E '...' | sed '{ ... }' | tar archive extract foo.tar.xz

Using some file-descriptor introspection trickery, none of the steps except for the last one would actually have to stream bytes through them.

2. One interesting thing about ps is that it takes two separate sets of switches—BSD switches and GNU switches. Given that any given user will only want to use one or the other, these two interfaces should be broken into two utilities (likely using argv[0] detection, like gzip(1) and zcat(1)), with separate man-pages. Setting which one plain "ps" means when ps is called TTY-interactively should be a configuration-file thing.

3. Look at the man-page for GNU coreutils ln(1) or cp(1). They're messes of compat-switches, and compat-switch aggregates, aimed at allowing you to reproduce the default behaviour of the OS you're used to on any-and-every OS you can compile coreutils for. This configuration doesn't belong in argv[]; it belongs in a ./configure script, or in a ~/.config/coreutils/ui-rc file. (Some of the switches are maybe for things you might want to do even in your initrd before you've got the rootfs mounted; those are what env-vars are for.)

4. rsync(1) has options for copying ACLs, copying Extended Attributes, "handling sparse files efficiently", and so on. rsync should just try to do these things automatically, and fall back to not doing them if the source or dest doesn't have support for them. There's no use-case where both the source and target support EAs but you don't want them copies. There's also no use-case where one or the other doesn't support EAs and so you want to fail the sync instead of copying. There's no need for these switches, just like there's no need for an FTP PASV switch. It can be detected.

---

As an aside:

> not knowing that GNU and at least one BSD tar know how to automatically select compression format in at least some cases

For extraction, sure. But why not for creation? RAR and Zip can pick the best compression they "know how to" do at the current moment, and offer compression speed/quality presets that actually involve picking different algorithms.

The real confusion over tar's compression switches is more fundamental; it comes from the fact that a tar archive is "wrapped in" an arbitrary compression-container file-format, without there being any standard for those to allow you to detect something as a "gzipped tar" rather than "gzipped opaque data", and thus the inability of tar, or your OS, to recognize an "[unknown compressor]ed tar" file.

The gordian knot of tar(1)'s switches is for tar—already having treated the compressor as a subprocess rather than a pipe-destination for a long time now—to just begin adding a "this is a tar archive with a compressed stream of archive files inside it" header to the outside of the compressed stream. Even though full backcompat is still possible after defaulting to such a change (user pref files! env vars! in-file hinting that the previous binary can recognize!), everybody's too lazy to want to make that sort of change.

[Hello71]

> A proper multi-subcommand refactoring of tar, I would think, might involve an interestingly different usage—a "fluent OOP interface" involving either a series, or pipeline, of invocations, all involving tar subcommands. For example:

... it was my understanding that the goal was to make the interface easier, not three times as complicated.

> 2. One interesting thing about ps is that it takes two separate sets of switches—BSD switches and GNU switches. Given that any given user will only want to use one or the other, these two interfaces should be broken into two utilities (likely using argv[0] detection, like gzip(1) and zcat(1)), with separate man-pages. Setting which one plain "ps" means when ps is called TTY-interactively should be a configuration-file thing.

"bsdps" and "gnups" seem much worse than "ps" and "ps -".

> 3. Look at the man-page for GNU coreutils ln(1) or cp(1). They're messes of compat-switches, and compat-switch aggregates, aimed at allowing you to reproduce the default behaviour of the OS you're used to on any-and-every OS you can compile coreutils for. This configuration doesn't belong in argv[]; it belongs in a ./configure script, or in a ~/.config/coreutils/ui-rc file. (Some of the switches are maybe for things you might want to do even in your initrd before you've got the rootfs mounted; those are what env-vars are for.)

cp I'll kind of buy, but ln? It's only got 14 real options, none of which can be described as a "compat switch". Again, I'll have to ask you for a specific example. Here's an example of a specific example: "cp -Q does <weird thing> that HP-UX does and nobody else".

> There's no use-case where both the source and target support EAs but you don't want them copies.

Security?

> There's also no use-case where one or the other doesn't support EAs and so you want to fail the sync instead of copying.

Wait, what? "fail silently"?

> There's no need for these switches, just like there's no need for an FTP PASV switch. It can be detected.

copying ACLs isn't like PASV, it's more like ASCII vs binary mode. trying to auto-detect makes the situation worse.

> The gordian knot of tar(1)'s switches is for tar—already having treated the compressor as a subprocess rather than a pipe-destination for a long time now—to just begin adding a "this is a tar archive with a compressed stream of archive files inside it" header to the outside of the compressed stream. Even though full backcompat is still possible after defaulting to such a change (user pref files! env vars! in-file hinting that the previous binary can recognize!), everybody's too lazy to want to make that sort of change.

how about "updating the compression algorithm requires everybody to install a new (de)compressor and until they do they can't open your files"?

[derefr]

To me, for CLI commands, "easier" means two things:

1. more learnable, which usually translates to more discoverable, which in turn translates to more orthogonally-decomposed and regular. You want the grammars, syntaxes, sets of verbs/subcommands, names for taken parameters, etc. of all the binaries on a system to obey the Principle of Least Surprise with respect to one-another, so you can learn the syntax for one binary and then reuse that learning on another binary. (Much more likely to be done in a BSD than in Linux, but still possible.)

2. more wrappable, which usually also translates to being more orthogonally-decomposed and regular. You want your binaries to provide an API not only for humans, but for anything that wants to wrap your command in a GUI, or in a friendlier CLI UI, or in a network service, or whatever else. (If you write your binary as mostly a library with a small binary driver, this is even better—see e.g. curl's libcurl—but this is incredibly rare for some reason, and it's a bit much to demand that people refactor their entire codebases this way.)

Being wrappable means that your binary itself is 100% allowed to be "dumb" and "tedious" for experienced users (like in my tar pipeline-UX example), because aliases or scripts or entire conventional-command packages can be built around your binary.

The fact that there's no e.g. `docker gc` subcommand built into docker(1) is a feature, not a bug; the docker(1) binary just provides a set of orthogonal primitive subcommands. Someone else then wrote a docker-gc package containing a configurable script that calls docker(1) a bunch of times.

There should certainly be a high-level UX that doesn't require three separate commands to create a tar file. But tar(1), the core "engine" handling creating that archive, should not be the binary providing that convenient CISC UX. (Maybe you could follow the git model and allow people to call installed "tar-foo" binaries using `tar foo`, but even this is a bit silly.)

But personally, in my mind, tar(1) itself should be a low-level implementation-detail sort of binary anyway, like mknod(8) or losetup(8). tar(1) only handles .tar files, and that's a silly UX for any user-visible task. The only time you already know you've got a .tar file, or want a .tar file, is in a script—and in a script, you want exactly the kind of verbosity, strictness, and interposed-shell-gloop flexibility I was talking about.

Meanwhile, what a user wants 99% of the time for their TTY-interactive use, is a command equivalent to the things a GUI archive-manager does. Users don't want or need tar(1); they want an xdg-archive(1) that uses libarchive.

> Security?

Not the right layer to enforce that in; that's what the [no_]user_xattr mount option is for. (Or, alternately, hierarchical xattr namespaces, with everything coming from foreign sources tainted into a quarantine namespace.)

> Wait, what? "fail silently"?

rsync(1) actually prints a ton of warnings (one for each file, in fact) when you tell it to copy EAs but it can't manage either the read or write step. But it doesn't fail. Because, like I said, there's no use-case. rsync(1) mostly isn't used TTY-interactively; it's used as a recurring batch job. If you said you wanted data+EAs the first time, and the remote's sysadmin remounts their computer's filesystem so EAs stop being available, you don't suddenly want to stop syncing the data. You just want a syslog full of errors telling you that you missed the EAs, plus smart logic such that you can message the other sysadmin telling them to fix their box, and then rsync(1) will gracefully just add the now-available EAs to the files rather than having to re-copy the files. Which... it does. So, great!

(I mean, I can see a use-case for rsync being told "these files should have EAs" and then performing its sync in two steps, where it copies the files from the remote to a local cache, and then only moves those files into place in the local dir if the EAs are there. This would be important if e.g. your local dir is a public NFS mirror of the remote and people will immediately start downloading and trusting your copies to be full-fidelity copies. But! This isn't rsync(1)'s job. This isn't the negotiated details of mechanism; this is policy—policy that can be, and should be, entirely enforced outside of rsync(1) itself. What you really want to do is to rsync(1) the remote to a local spool dir, and then have an fsevent listener watching that dir, checking the local copies in it for semantic-level validity, and then hard-linking those files into the NFS-export dir if-and-when they become valid.)

> copying ACLs isn't like PASV, it's more like ASCII vs binary mode. trying to auto-detect makes the situation worse.

EAs and ACLs are separate things (one is implemented in terms of the other, but they are separated semantically by almost all programs that handle them, and for good reason.) Allowing rsync(1) to blindly sync ACLs across hosts is a much more complex question than just allowing it to sync userland/"shell" EAs.

My first-pass design would be to just never do it ever, instead just inheriting the local effective ACLs rsync(1) is running under, unless it's clear from nsswitch that the local and remote are part of the same AD/LDAP domain and thus share security objects.

But even then, this gets into the domain of "security considerations for programs when you run them with superuser privileges, allowing them to manipulate security metadata", which is totally separate from the UX considerations of regular userland binaries. SMB has, like, seven interlocking protocols, implemented by smbd(8) through twenty-odd libexec-binaries—some run as root, some setuid, some in userland—required to ensure remote-RPC-exposed objects are seen to have the correct ACLs on all hosts. It's awful and ugly. rsync(1) doesn't need to be that. It's a userland binary, sitting in /usr/bin, for users to sync things and then own those synced copies. It doesn't need to be more than that.

> how about "updating the compression algorithm requires everybody to install a new (de)compressor and until they do they can't open your files"?

It doesn't, though; that's what I was talking about with 'in-file hinting that the previous binary can recognize'. You can create a "wrapper format" that doesn't literally 'wrap' your previous format in a container, but rather embeds itself as an extra block in some conventional place that all the old (de)compressors ignore. In a sense, you're encoding your new metadata using lossless steganography into the old format. This is how e.g. the various versions of ID3 tagging have been implemented: since there are many hardware MP3 players that can't be updated—and MP3 is not an extensible container—each update to the ID3 spec is instead done with a formatting change that those old players will just ignore.

In the case of tar(1), here's one possible implementation of that idea: let's say that all the compressor algorithms tar(1) currently supports have a common notion of (though different instructions for) building a Huffman prefix tree, and of throwing away said Huffman tree. You could just stick instructions to build a special kind of Huffman tree at the beginning of the compressed data, one that is a valid but improbable tree from the compressor's perspective (i.e. something that it would never emit itself, but will accept), and which is represented in the compressed data as a static bytestring (i.e. magic numbers.) Then you can add to libmagic, tar(1) itself, etc. a set of new "compressed tar archive" content-signatures—one for each compressor's instruction-sequence variant, all pointing to the same media-type.