[Toybox] RFC: "ps -o ?", "logger -p ?", "kill -s ?"

[Robert Thompson]

It's nice where the "what do I put here?" and the "that particular
argument isn't supported in this version" logic cases can be folded
together.  Just list valid choices for that argument, then terminates
unsuccessfully (non-zero error code, but without the normal "I didn't
understand you" error messages.

It is nice to be able to differentiate between known-unsupported
arguments and unrecognized arguments. '--foo: "x" is not supported in
this version', vs "--foo: unknown argument 'x'. Valid choices are a,
b, c, bar."

As a nice side effect,  the code doesn't need to recognize a special
list-options argument...





On 2/20/18, enh <enh at google.com> wrote:
> wasn't that the whole reason behind adding the suggestion to the
> syntax error message?
>
> ps: Missing argument to -o (see "ps --help")
>
> i think the only real problem is the old bug where commands like top
> don't show the -o/-O help from ps. (a quick workaround would be to
> mention the "see also" in the top help.)
>
>
> On Tue, Feb 20, 2018 at 10:43 AM, Rob Landley <rob at landley.net> wrote:
>>
>>
>> On 02/20/2018 12:15 PM, Rob Landley wrote:
>>> A lot of commands take a list of possible inputs to one of their options,
>>> and
>>> there should be a way to query "what are the inputs". The way qemu does
>>> it is to
>>> let you supply ? as the input (ala "qemu-system-i386 -M ?")
>>>
>>> The problem is ? is a shell wildcard so you have to quote it. Otherwise
>>> it works
>>> _almost_ all the time, and then barfs if you have a single character
>>> filename in
>>> your current directory because the shell swapped it out before running
>>> your command.
>>>
>>> Is there an obvious better api for this?
>>>
>>> Advantages of the qemu approach are A) a certain number of people out
>>> there are
>>> already familiar with this, B) if you see "ps -o ?" even once it's pretty
>>> easy
>>> to guess/remember what it does. Much more so than say "ps -o -".
>>> Disadvantage is
>>> shell wildcard...
>>>
>>> Hmmm...
>>
>> Ah, qemu seems to have noticed the wildcard problem, and changed their
>> recommendation:
>>
>>   $ qemu-system-i386 -M x
>>   qemu-system-i386: -M x: unsupported machine type
>>   Use -machine help to list supported machines
>>
>> Ok, I suppose the magic name "help" is reasonable...?
>>
>> (I could also output the list for any unknown type, but there should be an
>> error
>> message at the top, and then it's not "for i in $(ps -o helo)"; do az $i;
>> done"
>> scriptable.)
>>
>> (One thing I've wondered about is where to _document_ this, and the error
>> message telling you how to get help is the obvious place...)
>>
>> Rob
>> _______________________________________________
>> Toybox mailing list
>> Toybox at lists.landley.net
>> http://lists.landley.net/listinfo.cgi/toybox-landley.net
> _______________________________________________
> Toybox mailing list
> Toybox at lists.landley.net
> http://lists.landley.net/listinfo.cgi/toybox-landley.net
>