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Re: How to change environment from a module
- X-seq: zsh-workers 18039
- From: "Mark Hessling" <m.hessling@xxxxxxxxxx>
- To: zsh-workers@xxxxxxxxxx
- Subject: Re: How to change environment from a module
- Date: Tue, 31 Dec 2002 11:16:53 +1000
- Mailing-list: contact zsh-workers-help@xxxxxxxxxx; run by ezmlm
- Priority: normal
- Reply-to: m.hessling@xxxxxxxxxx
- Sender: m.hessling@xxxxxxxxxx
> On Dec 29, 7:32pm, Mark Hessling wrote:
> } [Bart wrote:]
> } > In general you shouldn't call bin_ functions directly. They
> } > should almost always be called only via the command execution
> } > code.
> } Why should these functions not be called directly ?
> Because they often depend on the generic command setup that is
> performed in the execution code in exec.c.
> } > It's very likely that your module should call zgetdir(&ds)
> before } > running the Rexx program and call restoredir(&ds)
> after it. }
> } But this is the only reason for running a Rexx interpreter
> within the } current process of the shell; to change the
> environment permanently.
> I can think of other reasons, such as avoiding the overhead of
> repeated forks and of reloading the interpreter.
Yes, but they are not the primary practical reasons from a user's
perspective; particularly one from an OS/2 background where the Rexx
interpreter there is an integral part of the shell. Its this behaviour I'm
trying to duplicate with zsh.
> } Based on this premise, then calling routines like zchdir()
> doesn't } go the whole way. ie if you have a chpwd() function in
> zshrc, then } zchdir() doesn't call it.
> That's true -- zchdir() is a function meant to be called by the
> zsh internals at a lower level than the command interpreter.
> } So again, how should one call the bin_*() functions directly
> from a } module as though a "cd" command or "export" command were
> executed } directly by the user ?
> This is akin to asking how to attach a clutch pedal to an
> autmobile with an automatic transmission. Just because there's a
> clutch plate in there somewhere doesn't mean there's an easy way
> to bolt new a lever to it. In fact, you're trying to connect an
> entire second engine to the drive chain, and wondering why the
> chassis wasn't designed for that.
> The best suggestion I can give you is:
> sprintf(command, "\\builtin cd %s", bslashquote(dirname, NULL
> , 0));
> execstring(command, 1, 0);
> Where it's up to you to be sure that the command buffer is large
Crude but very effective :-) Works like a charm! Also did the same with
"\\builtin export %s=%s", and it also works exactly how I wanted.
Many thanks Bart for your suggestions, the module works great.
One last question; naming standards for modules. Are third-party modules
allowed to start with "z" ? eg. I've called mine "zregina", so that the
"regina" executable will still be available as an external program.
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