On 5/25/23 6:29 AM, Koichi Murase wrote:
2023年5月24日(水) 22:27 Chet Ramey <chet.ra...@case.edu>:
[...]
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 ${(command)} would be explicitly unsupported even
though {(command)} is allowed for the brace grouping?
It means that left paren is no longer one of the valid characters that
can follow `${'. If you want that, use a subshell command after a space.
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.
It is, but that's not the code I'm talking about. Look at parse_comsub()
in parse.y and the places that call it.
The different characters that follow the open brace don't really have
any effect on the compound_list that gets parsed. They determine how the
parsed command is executed.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU c...@case.edu http://tiswww.cwru.edu/~chet/
