get output of a command in prompt

get output of a command in prompt

[arno.]

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Hi,
I want to get the output of a command in my prompt 
(actually, I want the temperature of my cpu in RPS1 if it is superior 
to a some predifined value).
So I have something like :
 RPS1="%2v"
 and 

precmd() {
    gettemp
}

with gettemp that gets temperature and puts it in psvar[2] if needed.

Today, I've seen in zsh user guide :

> Some people make the mistake of using it [precmd function] to set up a 
> prompt, but there are enough ways of getting varying information into a 
> fixed prompt string that you shouldn't do that unless you have very odd 
> things in your prompt.
http://zsh.sunsite.dk/Guide/zshguide03.html#l51

But I didn't find a better way to do what I want. Did I miss something, 
or is my goal something "very odd".

thanks 
arno

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Re: get output of a command in prompt

[Frank Terbeck]

arno. <arno.@no-log.org>:
[..get output of command into prompt..]

Take a look at this:

[snip]
zsh% PS1='$(printf "%s: %d" "This is a one" 1)-%% '
$(printf ": /home/hawk" "This is a one" 1)-% setopt promptsubst 
This is a one: 1-%
[snap]

Regards, Frank

Re: get output of a command in prompt

[arno.]

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Le Saturday 16 September 2006, à 21:01:55PM +0200, Frank a écrit : 
> arno. <arno.@no-log.org>:
> [..get output of command into prompt..]
> 
> Take a look at this:
> 
> [snip]
> zsh% PS1='$(printf "%s: %d" "This is a one" 1)-%% '
> $(printf ": /home/hawk" "This is a one" 1)-% setopt promptsubst 
> This is a one: 1-%
> [snap]

Yes, I've tried things like that, but the problem is that command output 
will be evaluated once, just when prompt is set up. It will not be 
evaluated each time prompt is displayed

arno

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Re: get output of a command in prompt

[Bart Schaefer]

On Sep 17,  4:14pm, arno. wrote:
}
} Le Saturday 16 September 2006, à 21:01:55PM +0200, Frank a écrit : 
} > zsh% PS1='$(printf "%s: %d" "This is a one" 1)-%% '
} > $(printf ": /home/hawk" "This is a one" 1)-% setopt promptsubst 
} > This is a one: 1-%
} 
} Yes, I've tried things like that, but the problem is that command output 
} will be evaluated once, just when prompt is set up.

Not true.  The quoting is important:  Note where single quotes (') have
been used and where double quotes have.  Compare:

PS1="$(printf '%s: %d' 'This is a one' 1)-%% " ;: This is the wrong way
PS1='$(printf "%s: %d" "This is a one" 1)-%% ' ;: This is the right way

} It will not be evaluated each time prompt is displayed

It will if the quoting is right and the promptsubst option has been set.

Question for zsh-workers:  Why is the prompt string being evaluated more
than once on every zle reset?

torch% PS1='z is $((++z)) %# '
z is $((++z)) % setopt promptsubst
z is 2 % echo I expect three
I expect three
z is 5 % 
z is 8 % echo I guess I should expect eleven
I guess I should expect eleven
z is 11 % 

This could be expensive for command substitutions in the prompt.

Re: get output of a command in prompt

[Dan Nelson]

In the last episode (Sep 17), arno. said:
> Le Saturday 16 September 2006, à 21:01:55PM +0200, Frank a écrit : 
> > arno. <arno.@no-log.org>:
> > [..get output of command into prompt..]
> > 
> > Take a look at this:
> > 
> > [snip]
> > zsh% PS1='$(printf "%s: %d" "This is a one" 1)-%% '
> > $(printf ": /home/hawk" "This is a one" 1)-% setopt promptsubst 
> > This is a one: 1-%
> > [snap]
> 
> Yes, I've tried things like that, but the problem is that command output 
> will be evaluated once, just when prompt is set up. It will not be 
> evaluated each time prompt is displayed

That example does evalute the prompt each time it's printed; you just
can't tell.  Try with a command that changes its output:

zsh% PS1='$(date)-%% ' ; setopt promptsubst
Sun Sep 17 12:06:02 CDT 2006-% <press enter>
Sun Sep 17 12:06:33 CDT 2006-% <press enter>
Sun Sep 17 12:06:34 CDT 2006-% 

Of course in this example you'd be better off using zsh's builtin
date-printing prompt escapes, but you get the idea.

-- 
	Dan Nelson
	dnelson@allantgroup.com

Re: get output of a command in prompt

[arno.]

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Le Sunday 17 September 2006, à 12:09:14PM -0500, Dan a écrit : 
> In the last episode (Sep 17), arno. said:
> > Le Saturday 16 September 2006, à 21:01:55PM +0200, Frank a écrit : 
> > > arno. <arno.@no-log.org>:
> > > [..get output of command into prompt..]
> > > 
> > > Take a look at this:
> > > 
> > > [snip]
> > > zsh% PS1='$(printf "%s: %d" "This is a one" 1)-%% '
> > > $(printf ": /home/hawk" "This is a one" 1)-% setopt promptsubst 
> > > This is a one: 1-%
> > > [snap]
> > 
> > Yes, I've tried things like that, but the problem is that command output 
> > will be evaluated once, just when prompt is set up. It will not be 
> > evaluated each time prompt is displayed
> 
> That example does evalute the prompt each time it's printed; you just
> can't tell.  Try with a command that changes its output:
> 
> zsh% PS1='$(date)-%% ' ; setopt promptsubst
> Sun Sep 17 12:06:02 CDT 2006-% <press enter>
> Sun Sep 17 12:06:33 CDT 2006-% <press enter>
> Sun Sep 17 12:06:34 CDT 2006-% 
> 
> Of course in this example you'd be better off using zsh's builtin
> date-printing prompt escapes, but you get the idea.

Oups,
looks like I did it wrong before.
It works now
thanx a lot

arno

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Re: get output of a command in prompt

[Phil Pennock]

On 2006-09-16 at 20:49 +0200, arno. wrote:
> So I have something like :
>  RPS1="%2v"
>  and 
> 
> precmd() {
>     gettemp
> }

> > Some people make the mistake of using it [precmd function] to set up a 
> > prompt, but there are enough ways of getting varying information into a 
> > fixed prompt string that you shouldn't do that unless you have very odd 
> > things in your prompt.
> http://zsh.sunsite.dk/Guide/zshguide03.html#l51
> 
> But I didn't find a better way to do what I want. Did I miss something, 
> or is my goal something "very odd".

I interpret the user guide text to mean "Don't set the prompt in
precmd()", given the following text: "It's a big nuisance having to
redefine precmd to alter your prompt --- especially if you don't know
it's there, since then your prompt apparently magically returns to the
same format when you change it."


So they're saying that instead of using:
 function precmd { RPS1="$(gettemp)" }
you should instead do exactly what you are doing.

For a distributed example of using precmd, see the various
prompt_*_setup routines; in particular, prompt_zefram_setup shows
something manipulating various $psvar values for later display in the
prompt.

Regards,
-Phil