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Re: hash not restored after running command -p

From: Chet Ramey
Subject: Re: hash not restored after running command -p
Date: Mon, 1 Nov 2021 14:11:03 -0400
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On 11/1/21 11:26 AM, Chet Ramey wrote:
> On 10/31/21 12:06 PM, Roger Morris wrote:
>> Thanks for the reply.  Though POSIX may allow this, still the last
>> line of the following example is rather unexpected behavior
>> $
>> $ echo echo MY LOCAL tmp/date SCRIPT > tmp/date
>> $ chmod +x tmp/date
>> $
>> $ PATH=.:/bin
>> $ date
>> Sun 31 Oct 2021 11:59:07 AM EDT
>> $ hash -l
>> builtin hash -p /bin/date date
>> $ cd tmp ; date ; cd ..
>> MY LOCAL tmp/date SCRIPT
> This seems weird and non-intuitive (why not use the hashed value?), but
> it's actually a special case that's handled explicitly in the code. If the
> PATH search that results in a value being put into the hash table finds `.'
> in the PATH before finding the full path, the hash table remembers that
> fact and -- as a special case -- checks whether `./name' is an executable
> file before returning the hashed value on subsequent lookups. It's strange,
> but everyone seems to do it.

Before we all pile on here, yes, I understand why we all do it. I still
think it's non-intuitive, but you have to behave as if the hash table
weren't there at all.

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/

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