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Date: Thu, 15 Jun 2000 14:42:30 -0700 (PDT)
From: Bart Schaefer <schaefer@brasslantern.com>
Sender: schaefer@aztec.zanshin.com
Reply-To: Bart Schaefer <schaefer@brasslantern.com>
To: Shao Zhang <shao@linux.cia.com.au>
cc: ZSH Mail List <zsh-users@sunsite.auc.dk>
Subject: Re: [OT] export http_proxy
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On Fri, 16 Jun 2000, Shao Zhang wrote:

>     I have a couple of isps on my linux box, and some of them need a
>     proxy setting. So nearly everytime I dial up, I have to export the
>     http_proxy in order to use it. Now is there an easy/smart way to do
>     this rather than doing it manually?

Use the `preexec' user-defined function.  You need to devise a test that
zsh can use to determine to which ISP you're presently connected; perhaps
something like

    function preexec() {
	case ${${(M)$(ifconfig ppp0):#addr:*}#addr:} in
	192.168.68.1) export HTTP_PROXY=192.168.68.215;;
	192.168.86.9) typeset +x HTTP_PROXY; unset HTTP_PROXY;;
	and-so-on) export HTTP_PROXY=and-so-forth;;
	esac
    }

However, it might be a bit expensive to run ifconfig before each and every
command, so you might instead try putting it in the `periodic' function
(so it gets updated every $PERIOD seconds, which you also need to set).

Or you could put it in a trap handler for e.g the USR2 signal and have a
script that runs when PPP comes up that does a "killall -USR2 zsh" to
cause all shells to update their environment.

To explain those hierographics (PWS's word) a bit:

	$(ifconfig ppp0)	Run ifconfig and return its output
				as an array of words

	:#addr:*		Select the word matching addr:*

	(M)			Keep only the selected (`M'atching)
				word, rather than deleting it

	#addr:			Remove leading addr: from that word
				leaving just the IP address

Simple, no?