Antw: [EXT] Re: declare XXX=$(false);echo $?

[Ulrich Windl]

Dale, thanks for explaining.

So basically the behavior is as documented (not a bug), but the design
decision was poor:

  declare a
  a=b

has a different semantic as
  declare a=b

which I consider to be bad.

Ulrich

>>> "Dale R. Worley" <worley@alum.mit.edu> schrieb am 02.12.2022 um 17:39 in
Nachricht <878rjpahfz.fsf@hobgoblin.ariadne.com>:
> Chet Ramey <chet.ramey@case.edu> writes:
>> On 12/2/22 5:28 AM, Ulrich Windl wrote:
>>> Surprisingly "declare XXX=$(false);echo $?" outputs "0" (not "1")
>>> There is no indication in the manual page that "declare" ignores the
>>exit code of commands being executed to set values.
>>
>> Why do you think it should? `declare' has a well-defined return status.
> 
> There it is, end of "SIMPLE COMMAND EXPANSION":
> 
>        If  there is a command name left after expansion, execution proceeds

> as
>        described below.  Otherwise, the command exits.  If one of  the  
> expan‐
>        sions  contained a command substitution, the exit status of the 
> command
>        is the exit status of the  last  command  substitution  performed.  

> If
>        there were no command substitutions, the command exits with a status

> of
>        zero.
> 
> and:
> 
>        declare [-aAfFgiIlnrtux] [-p] [name[=value] ...]
>        typeset [-aAfFgiIlnrtux] [-p] [name[=value] ...]
>             [...]
>               The return value
>               is 0 unless an invalid option is encountered, an attempt is 
> made
>               to define a function using ``-f foo=bar'', an attempt is made

> to
>               assign a value to a readonly variable, an attempt is made to 
> as‐
>               sign a value to an array variable without using the compound 
> as‐
>               signment  syntax  (see  Arrays above), one of the names is not

> a
>               valid shell variable name, an attempt is made to turn off  
> read‐
>               only  status for a readonly variable, an attempt is made to 
> turn
>               off array status for an array variable, or an attempt is made

> to
>               display a non-existent function with -f.
> 
> If you input "XXX=$(false)", there isn't a command name, it's a sequence
> of assignments, and "the exit status of the command is the exit status
> of the last command substitution performed".  But if you input "declare
> XXX=$(false)", you're executing the "declare" command, and the exit
> status doesn't depend on the command substitution.
> 
> Dale