Re: is this a rightful error ? i thought i can flat string much to declare , but it seems ..

[Greg Wooledge]

On Tue, Apr 11, 2023 at 12:05:17PM +0200, alex xmb ratchev wrote:
> $ var='a=( 1 2 3 ) b=( 4 5 5 )' ; declare -a "$var" ; declare -p a b
> bash: syntax error near unexpected token `)'

It would be helpful to see *which* of the three commands is actually
causing the error, by running them separately.

unicorn:~$ var='a=( 1 2 3 ) b=( 4 5 5 )'
unicorn:~$ unset a b
unicorn:~$ declare -a "$var"
bash: syntax error near unexpected token `)'
unicorn:~$ declare -p a b
declare -a a=()
bash: declare: b: not found

So, the command which gives the error is:  declare -a "$var"

My reading of the situation is that declare is seeing a string argument
that begins with a=( and ends with ), so it assumes that you're giving it
a single array definition for the variable "a", and that each of the
words inside the parentheses should be parsed and expanded to become
the elements of that array.

The parser fails when it hits the fourth word ")".

One may argue whether this behavior is right or wrong, but I find it
surprising that you expected this to work.  You're passing TWO separate
array variable definitions in one string argument.

I would pass them separately.

unicorn:~$ a1='a=(1 2 3)' a2='b=(4 5 5)'
unicorn:~$ declare -a "$a1" "$a2"
unicorn:~$ declare -p a b
declare -a a=([0]="1" [1]="2" [2]="3")
declare -a b=([0]="4" [1]="5" [2]="5")

By the way, you might be operating under the false assumption that this
is somehow safer than using eval, because you spelled it differently.
It's not any safer.

unicorn:~$ a1='a=(1 2 `date`)'
unicorn:~$ declare -a "$a1"
unicorn:~$ declare -p a
declare -a a=([0]="1" [1]="2" [2]="Tue" [3]="Apr" [4]="11" [5]="07:36:20" 
[6]="EDT" [7]="2023")

In fact, if you stop being all fancy, and just use eval in the first
place...

unicorn:~$ var='a=( 1 2 3 ) b=( 4 5 5 )'
unicorn:~$ eval "$var"
unicorn:~$ declare -p a b
declare -a a=([0]="1" [1]="2" [2]="3")
declare -a b=([0]="4" [1]="5" [2]="5")

... it actually works BETTER.