Dynamic parameters for PROMPT_SUBST functions

Dynamic parameters for PROMPT_SUBST functions

[Sebastian Stark]

Hello,

I am trying to have a function call in my prompt that gets the return 
value of the last command as a parameter (%?).

However I am having trouble to get this right. Instead of an actual 
number, what is handed to the function is the literal string %?.

Is there anything I can do better or is this just not possible?

I could probably use $? in the function itself, but that sounds a bit 
fragile to me because I maybe get a different value of $?.

In this example I write the parameter to a file, because if I just print 
it it would get printed as a literal %? and expanded later and thus hide 
the issue I am facing


% zsh -f
% x(){print $1 >>/tmp/lll}
% setopt PROMPT_SUBST
% PROMPT=$'$(x %?) %m%# '
  % cat /tmp/lll
%?


Thanks for any hints.

Sebastian

Re: Dynamic parameters for PROMPT_SUBST functions

[Lawrence Velázquez]

Hi Sebastian,

> On Jun 19, 2020, at 2:32 AM, Sebastian Stark <sstark+zsh@mailbox.org>
> wrote:
> 
> I am trying to have a function call in my prompt that gets the
> return value of the last command as a parameter (%?).
> 
> However I am having trouble to get this right. Instead of an actual
> number, what is handed to the function is the literal string %?.

Yes, that is because the PROMPT_SUBST expansions (parameter, command,
and arithmetic) are done before the percent-escape sequences are
expanded.

vq

Re: Dynamic parameters for PROMPT_SUBST functions

[Daniel Shahaf]

Sebastian Stark wrote on Fri, 19 Jun 2020 08:32 +0200:
> I am trying to have a function call in my prompt that gets the return 
> value of the last command as a parameter (%?).

What would you do with «%?» if you could get its value?

> In this example I write the parameter to a file, because if I just print 
> it it would get printed as a literal %? and expanded later and thus hide 
> the issue I am facing

You could also print to /dev/tty.

Cheers,

Daniel

Re: Dynamic parameters for PROMPT_SUBST functions

[Sebastian Stark]

Am Freitag, den 19. Juni 2020 um 13:04 schrieb Daniel Shahaf:
>Sebastian Stark wrote on Fri, 19 Jun 2020 08:32 +0200:
>> I am trying to have a function call in my prompt that gets the return
>> value of the last command as a parameter (%?).
>
>What would you do with «%?» if you could get its value?

I would try to split it into signal and return value information, so I 
do not get "130" if I ctrl-c, but something like 0 and INT.

>> In this example I write the parameter to a file, because if I just print
>> it it would get printed as a literal %? and expanded later and thus hide
>> the issue I am facing
>
>You could also print to /dev/tty.

That's at least something I can take away from this, thanks :)


Sebastian

Re: Dynamic parameters for PROMPT_SUBST functions

[Daniel Shahaf]

Sebastian Stark wrote on Fri, 19 Jun 2020 19:08 +0200:
> Am Freitag, den 19. Juni 2020 um 13:04 schrieb Daniel Shahaf:
> >Sebastian Stark wrote on Fri, 19 Jun 2020 08:32 +0200:  
> >> I am trying to have a function call in my prompt that gets the return
> >> value of the last command as a parameter (%?).  
> >
> >What would you do with «%?» if you could get its value?  
> 
> I would try to split it into signal and return value information, so I 
> do not get "130" if I ctrl-c, but something like 0 and INT.

That information isn't available via %?:
.
    % PS1='%?%# '
    0% perl -E 'kill 9, $$' 
    zsh: killed     perl -E 'kill 9, $$'
    137% perl -E 'exit (9 + 128)' 
    137% 

Note how %? expanded to the same value in both cases.

The information is not available via $pipestatus either.

However, the "killed" (or "interrupted", etc) message is only printed
when a job exited with a signal.

Furthermore, if you don't care about programs whose exit codes just
happen to be in the 128+signal range, you can do:
.
    % setopt promptsubst
    % PS1='$signals[1 + ($? - 128)]%# '
    % (exit 137)
    zsh: exit 137   ( exit 137; )
    KILL% 

The variable «$signals» is predefined.  Just make sure that $? is the
right value.  (If you have other $(…) in there, they might overwrite
«$?»?  I haven't tested.)

And to show the numeric exit code when there isn't a signal associated,
using the ternary condition syntax:
.
    PS1='${signals[1 + ($? - 128)]:-"%(?..%?)"}%# '

This does not handle the case that ${signals[…]} is EXIT, ZERR, or DEBUG.

Cheers,

Daniel

Re: Dynamic parameters for PROMPT_SUBST functions

[Sebastian Stark]

Am Samstag, den 20. Juni 2020 um 13:06 schrieb Daniel Shahaf:
>Sebastian Stark wrote on Fri, 19 Jun 2020 19:08 +0200:
>> Am Freitag, den 19. Juni 2020 um 13:04 schrieb Daniel Shahaf:
>> >Sebastian Stark wrote on Fri, 19 Jun 2020 08:32 +0200:
>> >> I am trying to have a function call in my prompt that gets the return
>> >> value of the last command as a parameter (%?).
>> >
>> >What would you do with «%?» if you could get its value?
>>
>> I would try to split it into signal and return value information, so I
>> do not get "130" if I ctrl-c, but something like 0 and INT.
>
>That information isn't available via %?:
>.
>    % PS1='%?%# '
>    0% perl -E 'kill 9, $$'
>    zsh: killed     perl -E 'kill 9, $$'
>    137% perl -E 'exit (9 + 128)'
>    137%
>
>Note how %? expanded to the same value in both cases.

Yes, I noticed that this is not entirely clean.

>    % setopt promptsubst
>    % PS1='$signals[1 + ($? - 128)]%# '
>    % (exit 137)
>    zsh: exit 137   ( exit 137; )
>    KILL%
>
>The variable «$signals» is predefined.  Just make sure that $? is the
>right value.  (If you have other $(…) in there, they might overwrite
>«$?»?  I haven't tested.)

Thanks for this, I didn't know about the signals array. Also, your 
solution looks pretty much like what I was looking for.

However, in my prompt variable this expands to the number, not the 
signal name. Your code does the right thing when used as PS1 without 
anything else, but not in combination with my other things in there. 

For now I will put that on my pile of unfinished things, as it seems to 
be complicated for little outcome.

Thanks again!


Sebastian