Re: % in $PATH

[Stephane Chazelas <stephane.chazelas@gmail.com>]

2014-11-10 21:20:02 +0800, Herbert Xu:
> On Wed, Nov 05, 2014 at 11:59:47AM +0000, Stephane Chazelas wrote:
> > Hello,
> > 
> > ash/dash have a nice feature that allows to have:
> > 
> > PATH=/bin:%builtin:/usr/bin:/some/dir%func:/sbin
> > 
> > To have commands in /bin take precedence over builtins and
> > files in /some/dir being looked up for autoloaded functions (a
> > bit like FPATH in ksh/zsh).
> > 
> > That's nice but the way it is implemented, that means that %
> > characters in $PATH cause problems. See for instance:
> > 
> > http://unix.stackexchange.com/questions/126955/percent-in-path-environment-variable
> 
> I'm inclined to just kill this feature, or at least make it a
> configuration option that's disabled by default.
[...]

Though I'd agree there's little chance of many people using it as
the documentation about it has been removed in dash, I don't
think there's any harm in leaving it in but implemented the way
I suggest.

It's useful as an equivalent to bash's exported functions (and
is a better/safer approach IMO) as an instrumentation tool.

Example: redefine "echo" as a Unix conformant one before running
something that expects a Unix conformant "echo":

$ printf '%s\n' 'echo() { local IFS=" "; printf "%b\n" "$*"; }' > echo
$ PATH=$PWD%func:%builtins:$PATH dash -c 'echo "-n\c"; echo x'
-nx

I don't see the point in keeping it if it's to make it disabled
by default though (unless we add an equivalent of BASHOPTS which
can be used to turn it on via the environment)

-- 
Stephane