2023年5月24日(水) 22:27 Chet Ramey <[email protected]>:
> > [...]
>
> Thanks for testing it.
Thank you for all the explanations and clarifications.
> Both are valid, but don't get too fond of ${(command)} -- I'm going to
> remove it in favor of people using ${ (command); } if they want a subshell.
Does that mean ${(command)} would be explicitly unsupported even
though {(command)} is allowed for the brace grouping? Would other
cases without semicolons, such as ${ if ...; then ...; fi }, also be
going to be removed?
> > Then, can I understand the grammar in the following way? First, there
> > are two types of nofork command substitutions:
> >
> > ${ compound_list }
> > ${| compound_list }
> >
> > where `compound_list' is what is defined by EBNF in POSIX XCU 2.10.2.
>
> You could always look at the shell grammar:
>
> [...]
>
> funsub: DOLBRACE compound_list '}'
> {
> $$ = $2;
> }
> | DOLBRACE newline_list '}'
> {
> $$ = (COMMAND *)NULL;
> }
OK, I haven't checked the grammar definition in the source code. I now
looked into parse.y, but it doesn't seem to be so clear to me what
would be the distinction among the variations of C = <space>, <tab>,
<newline>, `(', and `|' for `${C command; }' just by looking at the
definition. It seems to be processed on subst.c:6880 semantically.
Anyway, I'm satisfied now.
Thank you.
--
Koichi
