Re: symlink chain.

[Ray Andrews <rayandrews@eastlink.ca>]

On 01/02/2015 11:17 PM, Bart Schaefer wrote:
> torch% /foo() { print Look, I have a slash. }
> torch% whence -v /foo
> /foo is a shell function
> torch% whence -mv '/fo?'	# won't work with the above change
> /foo is a shell function
>
> PWS's change for -a only works because it happens so late in the algorithm
> that there is nothing left but path to search, and no patterns left to be
> tried.
>
As you say.  The test for the leading slash is obviously a bit of a 
band-aid.  I'd have expected the -m and/or -a code to be able to look at 
a full path without that being any sort of problem--it wouldn't have any 
work to do so it would get the day off, but neither would it force a 
false negative return (rather the way that -s just does nothing when it 
has nothing to do, but it doesn't break anything, either).

All I can say with conviction is that 'whence -m /usr/bin/zsh' should 
not return nothing, because the file exists on the path and is a link to 
an executable and has a legitimate search target string. It should be 
found.  It is pathetic that if I was doing a whole list of whences with 
the -m or -a switches, and then at some point I entered a canonical 
filename (whereas up to that point it was more the pattern search 
thing), I get nothing because, oops, I forgot to remove the -m and/or 
-a.  Or this alias:

     alias wenceslas='whence -mavs'

... doesn't work with a canonical filename :(

Whence is a wrench.  Wrenches should not be hard to understand and they 
shouldn't have any gotchas.  It should take two minutes to know how 
whence works and it should work every time in an intuitive way.  No 
switch should break anything.  To be theatrical, I think if zsh made 
wrenches, they would only tighten metric nuts on Tuesdays and they would 
only loosen fractional nuts on long weekends  *but* you could lay a zsh 
wrench on top of your engine and it would do a full valve job for you 
and do it right (except on Fridays).  Pardon ;-)

BTW, for what it's worth, in one of my wrappers I do this:

    find_count=`whence -ma "$1" | wc -l`

... I'm just using whence at that point to search for and count targets 
which then are given the 3d degree:

    $ i ,v zsh

    Current path:

    /aWorking/Bin
    /usr/local/bin
    /usr/sbin
    /usr/bin
    /sbin
    /bin

    Aliases, Functions, Builtins, Scripts or Binaries: Found 3 matches:

    (1)TYPE: zsh is /usr/local/bin/zsh ->
    /usr/local/bin/zsh-5.0.7-165-g2194da1:
    LISTING: lrwxrwxrwx 1 22 2014-12-30-19:59:18 /usr/local/bin/zsh ->
    zsh-5.0.7-165-g2194da1*
    LINK CHAIN:
    l zsh -> zsh-5.0.7-165-g2194da1
    CONTENT: inode/symlink; charset=binary

    (2)TYPE: zsh is /usr/bin/zsh -> /usr/local/bin/zsh-5.0.7-165-g2194da1:
    LISTING: lrwxrwxrwx 1 28 2014-02-09-19:29:52 /usr/bin/zsh ->
    /etc/alternatives/zsh-usrbin*
    LINK CHAIN:
    l zsh -> /etc/alternatives/zsh-usrbin
    l   zsh-usrbin -> /usr/local/bin/zsh
    l     zsh -> zsh-5.0.7-165-g2194da1
    CONTENT: inode/symlink; charset=binary

    (3)TYPE: zsh is /bin/zsh -> /usr/local/bin/zsh-5.0.7-165-g2194da1:
    LISTING: lrwxrwxrwx 1 21 2014-02-09-19:29:52 /bin/zsh ->
    /etc/alternatives/zsh*
    LINK CHAIN:
    l zsh -> /etc/alternatives/zsh
    l   zsh -> /usr/local/bin/zsh
    l     zsh -> zsh-5.0.7-165-g2194da1
    CONTENT: inode/symlink; charset=binary

... and sometimes I want to give the 3d degree to a single specified file:


     $ i ,v /usr/bin/zsh

... and that's when it bugs me that the 'whence -ma' test fails.  I can 
work around it, but I shouldn't hafta. -m and -a should be smart enough 
to handle a canonical filename.

(BTW The above is my idea of one-stop shopping for information about a 
command ;-)