On 19/04/2023 08:46, wwp wrote: > Hello lejeczek, > > > On Wed, 19 Apr 2023 08:10:16 +0200 lejeczek <peljasz at yahoo.co.uk> wrote: > >> On 19/04/2023 08:04, wwp wrote: >>> Hello lejeczek, >>> >>> >>> On Wed, 19 Apr 2023 07:50:29 +0200 lejeczek via CentOS <centos at centos.org> wrote: >>> >>>> Hi guys. >>>> >>>> I cannot wrap my hear around this: >>>> >>>> -> $ unset _Val; test -z ${_Val}; echo $? >>>> 0 >>>> -> $ unset _Val; test -n ${_Val}; echo $? >>>> 0 >>>> -> $ _Val=some; test -n ${_Val}; echo $? >>>> 0 >>>> >>>> What is this!? >>>> How should two different, opposite tests give the same result >>>> Is there some bash option which affects that and if so, then what would be the purpose of such nonsense? >>> Surround ${_Val} with double quotes (as you should) and things will be different: >>> >>> $ unset _Val; test -n "${_Val}"; echo $? >>> 1 >>> >>> Now you get it? :-) >>> >>> >> I don't know, am not sure, I remembered it differently, did not think enclosing quotes were necessary(always?) for that were {} > {} does not prevent this (at least not in bash): > > $ FOO="a b" > > $ test -z $FOO > bash: test: a: binary operator expected > > $ test -z ${FOO} > bash: test: a: binary operator expected > > Because after $FOO or ${FOO} variable expansion, bash parsed: > test -z a b > 'b' is unexpected, from a grammar point of view. > > Quoting is expected, here: > $ test -z "$FOO" > <no error> > > When FOO is unset, apparently it's a different matter, where you end up > with $?=0 in all unquoted -n/-z cases, interestingly. I could not find > this specific case in the bash documentation. That may not be portable > to other shells, BTW. I only use {} when necessary (because of what > bash allows to do between {}, plenty!, or when inserting $FOO into a > literal string that may lead the parser to take the whole string for a > variable name: echo $FOObar != echo ${FOO}bar). > > > Regards, There is a several ways to run tests in shell, but 'test' which is own binary as I understand, defeats me.. in those three examples - regardless of how one can "bend" quoting & expanding - the same identical variable syntax is used and yet different tests render the same result. I thought 'test' broke and I had remembered it differently - meaning 'test' used to give results I thought it did - or perhaps some 'shopt' changed and affected its behavior. I'd expect a consistency, like with what I usually do to test for empty var: -> $ export _Val=some; [[ -v _Val ]]; echo $? 0 -> $ unset _Val; [[ -v _Val ]]; echo $? 1 Learning, re-learning, round & round it goes.. thanks, L.