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Re: FAQ title bar answer using chpwd()

Andrew Janke wrote on Fri, Mar 06, 2015 at 22:40:11 -0500:
> Hi, ZSH workers,
> I have a question about an answer in the ZSH FAQ. Is this the right
> list to ask about it?
> http://zsh.sourceforge.net/FAQ/zshfaq03.html#l23

Personally I'd have addressed zsh-users.

> Answer 3.6 suggests using chpwd() to emit terminal control sequences
> to update the title bar for Apple's Terminal.app. This probably
> isn't the right place to do it, because cd's can happen inside
> functions, pipelines, and so on whose output is going to be captured
> for use elsewhere. The terminal control sequences will contaminate
> the captured output instead of going to the terminal.
> There's at least one place in the wild where this causes an issue,
> with Android development scripts:
> https://github.com/robbyrussell/oh-my-zsh/issues/3524

We had a similar issue at Subversion: http://svn.apache.org/r1643793

> The prompt or other known user-interaction output points are
> probably the only safe place to emit terminal control sequences like
> this. So precmd() is probably a better choice than chpwd() for this.
> It seems like chpwd() should probably not be used to do anything
> that emits to stdout, in case it's being captured.
> Should the FAQ answer be updated to reflect this?

Why is a chpwd() hook set within the context of the Android scripts in
the first place?  Is it because they get sourced instead of executed?
If so, they really should switch to the ssh-agent/gpg-agent model, of
[eval `script`] instead of [source 'script'].

In the meantime, they can do something like:
[ -n "$ZSH_VERSION" ] && cd() { builtin cd -s "$@" }


Incidentally, another possible fix would be to have the FAQ recommend to
have the control sequences be printed to the controlling terminal,
rather than to stdout.  That would cause a different problem: instead of
contaminating the output, the terminal title might be wrong if a script
did 'cd' and then exited without changing back to the interactive user's
directory, as in '(cd ..)'.



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