From: "Bart Schaefer" <schaefer@candle.brasslantern.com>
To: nik@linna.com, zsh-workers@sunsite.auc.dk
Subject: Re: The mystery of deferred prompt evaluation
Date: Mon, 31 May 1999 09:20:02 +0000 [thread overview]
Message-ID: <990531092002.ZM4475@candle.brasslantern.com> (raw)
In-Reply-To: <374DBCEE.69426B26@linna.com>
On May 27, 2:45pm, Nik Gervae wrote:
} Subject: The mystery of deferred prompt evaluation
}
} PROMPT_LEN=3
} PROMPT_DYN='%${PROMPT_LEN}C'
} PROMPT='%0(#..)${PROMPT_DYN}% '
}
} I get the really cool feature of being able to change PROMPT_LEN at
} any point and having my prompt adjust how much of my path it shows.
} Oddly enough, this only works if I put the %(...) construct before
} the parameter reference in the prompt, if that isn't there then my
} prompt ends up being the literal text of the definition, with the
} parameter not getting expanded. I might add that in 3.1.5 the latter
} behavior is always the case (which I when I first noticed this).
You're making use of an undocumented (mis)feature. You've relied on
two levels of parameter expansion, which you're getting in 3.0.x only
by accident.
} Does anyone know:
}
} a) Why I shouldn't be able to defer parameter expansion in my
} prompts in general?
You should, by use of the PROMPT_SUBST option, which you must have set
for any of this to happen even in 3.0.x. What you can't expect is that
the expansion of a parameter is re-expanded when it happens to have a
$ in it, unless you tell zsh to do so.
} b) Why in 3.0.5 it works with %(...) before the parameter
} but not without?
} c) Why it doesn't work at all, ever, in 3.1.5?
The 3.0.x prompt code calls itself recursively when it encounters a %( )
construct, which causes the PROMPT_SUBST option to be applied twice (or
more, if the nesting is deeper). This was not supposed to happen, and
in fact is a bug if you're trying to get a prompt that contains a $ or
other special character. Prompt display has been completely rewritten
for 3.1.5, so this no longer occurs.
} d) How I can get this behavior back? :-)
Use the (e) parameter flag, like so:
PROMPT_LEN=3
PROMPT_DYN='%${PROMPT_LEN}C'
PROMPT='${(e)PROMPT_DYN}% '
Or simply eliminate one level of indirection:
PROMPT_LEN=3
PROMPT='%${PROMPT_LEN}C% '
--
Bart Schaefer Brass Lantern Enterprises
http://www.well.com/user/barts http://www.brasslantern.com
prev parent reply other threads:[~1999-05-31 9:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-05-27 21:45 Nik Gervae
1999-05-31 9:20 ` Bart Schaefer [this message]
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