Re: [[ -x =command ]]

[Stephane Chazelas <Stephane_Chazelas@xxxxxxxx>]

On Wed, Oct 17, 2007 at 07:34:32AM -0400, Matthew Wozniski wrote:
> On Wed, Oct 17, 2007 at 10:44:14AM +0100, Stephane Chazelas wrote:
> > zmodload -i zsh/parameters
> > export PAGER=\
> > ${commands[most]:-\
> > ${commands[less]:-\
> > ${commands[w3m]:-\
> > ${commands[pager]:-\
> > more}}}}
> > 
> > or, portably:
> > 
> > for PAGER in most less w3m pager more; do
> >   command -v "$PAGER" > /dev/null 2>&1 && break
> > done
> > export PAGER
> >   
> > as I don't think you need the full path in $PAGER.
> 
> Hm.  `command -v more' and `$commands[more]' aren't equivalent, it
> seems.
> 
> mastermind% echo $commands[ls]
> /bin/ls
> mastermind% command -v ls
> alias ls='ls --color=auto -B'
> 
> So, just for the sake of argument, if one were to have aliased `most'
> to `less' on a machine that didn't have most, the first form would
> work properly, but the second would result in a false positive and
> fail when an application tried to use $PAGER, since no alias expansion
> would be performed.
[...]

You're right,

You could use whence -p instead, but then it would no longer be
portable.

-- 
Stéphane