@JeffSchaller packages.ubuntu.com will provide version numbers for packages currently supported.

@DKBose thank you for the ubuntu packages link!

@StephenKitt I'm curious how you intuited that this user was running Debian 9. I would have liked to see the OP update their post with the version number.

@JeffSchaller the version number of the installation candidate for the tor package uniquely determines the release being used (see Madison).

@StephenKitt would you object to adding that link to your Answer?

(by "link" I mean the hyperlink and the inference you made)

@JeffSchaller done!

@StephenKitt outstanding; thank you, sir!

That is a bug, not a feature.

@terdon that cd --help is more than a terminal long?

@terdon opinion-based ;-)

But technically there’s no basis for the assertion that --help is only available on external commands.

@derobert for one thing. But also that I need to use cd -- --help to move into ./--help!

@terdon or cd ./--help ... that's a problem with having file names like that in general :-(

rmdir and/or mv will have the same issue (can't think of any other commands you'd want to run upon seeing a ./--help)

Granted, if you have a directory called --help, you need all the help you can get, but still.

It just seems odd that something as basic as cd would take double hyphenated options in the first place.

And, of course, that isn't actually mentioned in the bleedin' help page!

Yeah, it is a bid odd cd has options.

I do find -P very useful.

@terdon you might say you have too much help!

I was about to say some of the cd options are useful!

@StephenKitt But --style? Why?

And undocumented ones like --help are just wrong! Says I.

If you're going to do that, at least mention it in the help page

@terdon uniformity? But yes, it is somewhat silly.

$ cd --help
cd: cd [-L|[-P [-e]] [-@]] [dir]
    Change the shell working directory.

    Change the current directory to DIR.  The default DIR is the value of the
    HOME shell variable.

    The variable CDPATH defines the search path for the directory containing
    DIR.  Alternative directory names in CDPATH are separated by a colon (:).
    A null directory name is the same as the current directory.  If DIR begins
    with a slash (/), then CDPATH is not used.

    If the directory is not found, and the shell option `cdable_vars' is set,

You'd think the option that was just used to invoke the manual would be mentioned in said manual!

Shrug it's already too long! And if you just used --help, presumably you already know that option...

does it do the same thing if you give it any other invalid option?

No

(maybe you're falling through a case statement)

$ cd --usage
bash: cd: --: invalid option
cd: usage: cd [-L|[-P [-e]] [-@]] [dir]

(You get the same output with cd --ohnoes)

That one could certainly mention --help

@derobert Ah, but if I hadn't? If I was one of the many unfortunate individuals who don't have a @StephenKitt to educate them, how would I even know it existed?

because GNU has taught you to run --help against anything & everything, apparently :)

Don't loads of GNU tools have -? instead?

Or -h

true --help

@terdon Sometimes those are short versions of --help. I think the GNU standard is --help

gnu.org/prep/standards/html_node/…

GNU standard is probably info help.

GNU being what it is and all :)

--version and --help are the two standard options listed

man -w

(And an odd thing suggesting CGIs should take --help in the URL!)

@terdon the --help option is fully documented. Start (execute)info and select Common Options where you will find the --help option documented for all GNU executables.

@StephenKitt The --help option is hard-wired into executables (programs) not necessarily built-ins. For example: echo has no help option (never had), but the executable /bin/help does. Try /bin/echo --help

Sorry, there is no /bin/help executable, I meant to say /bin/echo there, please s,/bin/help,/bin/echo,.

@Isaac hmm? all I did was give a counter-example to the claim that only external commands had --help.

@Isaac echo is, I think, one of the few bash builtins that doesn't. Probably because people love (for obvious reasons) using echo "$var" in place of printf '%s\n' "$var"

@terdon no, GNU doesn't use --? or -h usually. Those are Windows™ solutions. AFAICT.

Windows would be /h or /?. -h and -? are Unix, when you don't have long options.

I suppose Unix doesn't actually stop one from creating a directory called --help?

@FaheemMitha it doesn’t

Though it's not clear how to actually create it, since mkdir --help...

@FaheemMitha Yep. You can't have a file/directory called ., .., or containing /, or containing NUL (ASCII 0). Other than that, POSIX says all is OK.

@FaheemMitha mkdir ./--help ought to work.

@derobert or NUL?

@derobert Ah.

@StephenKitt right, or NUL.

And you can hack your file system to have a file name containing /, but then things get messy.

I imagine you could, depending on the FS, hack it to have a name with a null in it too.

Or named . or ..

@derobert yes, but the name can’t be returned in full by system calls; that’s not a problem with /.

Or a Unicode symbol that looks like a slash but isn't

And of course if you do any of those FS hacks, I doubt POSIX even guarantees you get to keep both pieces when your system breaks.

thought I had one in unix.stackexchange.com/questions/347484/… but apparently not

@JeffSchaller I've used those on purpose :-) They work fine.

See

for similar shenanigans

Just think of the fun that would ensue if you dared link . and .. to the wrong directories...

@derobert hah yes

with even more fun because of the special-case handling of . in at least some scenarios

(so . will mean different things depending on the program!)

Yep! Absolute confusion achieved!

A trick commonly deployed when I was at university was to create a directory named ~ inside users’ home directories, for similar reasons...

I hope no one tried rm -Rf ~ — a command no one should run...

cd ~/~ -- a directory with wings!

@Isaac certainly not Windows. I don't know anything about Windows, and certainly not about CLI stuff on Windows.

@StephenKitt @StephenKitt I may have misunderstood that comment.

@StephenKitt Maybe just spice it up a notch by creating a file in it called *.

@Kusalananda the objective was to suggest that users’ home directories were empty ;-)

@StephenKitt Ah.

Surprisingly got an offer to help with Lua. From an actual LuaTeX user.

github.com/luarocks/luarocks/issues/1033

That almost never happens.

Maybe it's just an elaborate leg-pull.

Hmm, a Brazilian mathematician (I think), I can't make out Portuguese very well.

@terdon My memories of WIndows are some years old (and fading, it seems). The correct use there is /h or /?. You are correct -? and -h are Unix but not universal I believe. At least not defined in POSIX: pubs.opengroup.org/onlinepubs/9699919799/basedefs/…

@FaheemMitha Need help with Brazilian? I may help, if you ask.

No idea. Last time I was a Windows user was 1998.

And while I did do a little bit of DOS, pre Windows, it wasn't much more than cd (or whatever the equivalent was, chdir?) and dir commands. So all my CLI knowledge comes from the Linux world, I am very unlikely to be confused by Windows memories :)

@terdon Maybe, but were is it defined that "the common" help option is -h ? I can not find it.

@terdon Only specific to IBM AIX (in some programs): aix.polarhome.com/service/man/…

@terdon At least ls doesn' t use -h for help. In any of its implementations.

@terdon And touch use -h for --no-dereference, clearly not for help.

Nobody? Fine, bye.

Guys.... ecr.us-west-2.amazonaws.com is ECR end point

What is the terminology used to refer 11122233344555.dkr.ecr.us-west-2.amazonaws.com

Docker registry end point?

@Isaac What's the issue? If there's a standard option for getting help from a utility? No, there is no such thing.

@Kusalananda There is no issue, some people here were discussing the --help use, it lead me to other alternatives, no issue at all. Seems like there is no interest. Fine, thanks, bye.

@MichaelHomer Thanks and sorry, in case you can see this.

@overexchange I am happening to read about docker. But I don't know the answer. I guess, the URL of the docker registry?

I wish one day I can use AWS

I am reading a book on docker, and it uses Flask as an example. So I am reading a bit about flask right now

Basically how to use docker in the stages of the lifecycle of software engineering.

which probably many of you already use on a daily basis

@StackExchangeforAll Good start would a case study on plural sight: "Continuous delivery using Docker and Ansible"

root@Jiji:~# mount -o degraded /backup/ gives a brilliant systemd response:

it mounts, then...

Jan 21 17:28:22 Jiji systemd[1]: backup.mount: Unit is bound to inactive unit dev-disk-by\x2duuid-b162055b\x2da73c\x2d4958\x2d98a7\x2dc6ad57867506.device. Stopping, too.
Jan 21 17:28:22 Jiji systemd[1]: Unmounting /backup...
Jan 21 17:29:05 Jiji systemd[1]: Unmounted /backup.

... umm, thanks?

@Isaac Hi, I just saw this. I have no idea which is the more common option. I just said I thought many GNU tools use -?, but that was probably wrong.

Well, found a way: