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Re: Empty ""s in ARG in ${x:+ARG} expand to no words instead of the empt
From: |
Chet Ramey |
Subject: |
Re: Empty ""s in ARG in ${x:+ARG} expand to no words instead of the empty word if prepended/appended with space |
Date: |
Sat, 21 Jul 2018 11:33:18 -0400 |
User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
On 7/21/18 12:44 AM, Bob Proulx wrote:
> Denys Vlasenko wrote:
>> $ f() { for i; do echo "|$i|"; done; }
>> $ x=x
>> $ e=
>> $ f ${x:+ ""}
>> ^^^^^^^^^^^ prints nothing, bug?
>>
>> $ ${x:+"" }
>> ^^^^^^^^^^^ prints nothing, bug?
>
> Insufficient quoting. That argument should be quoted to avoid the
> whitespace getting stripped. (Is that during word splitting phase
> using the IFS? I think so.)
Even if the whitespace gets stripped out, the quoted null string should
result in an empty argument. Different shells are inconsistent about this,
but I believe that if word splitting occurs, the empty string (or "$e",
anything that expands to an empty string) should result in a null word.
--
``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/