On Thu, Mar 6, 2025, at 9:06 PM, Kaz Kylheku wrote:
> But Bash cannot do this. The reason is that brace expansion is already
> a deviation from POSIX.
POSIX.1-2024 does permit brace expansion syntax as an extension,
although it doesn't use the term "brace expansion" or prescribe any
specific semantics. The description of the syntax doesn't allow
'{abc}' to expand to 'abc'.
When the expansion occurs in a context where field splitting
will be performed, a word that contains all of the following
somewhere within it, before any expansions are applied, in
the order specified:
- an unquoted <left-curly-bracket> ('{') that is
not immediately preceded by an unquoted <dollar-sign>
('$')
- one or more unquoted <comma> (',') characters or
a sequence that consists of two adjacent <period>
('.') characters surrounded by other characters
(which can also be <period> characters)
- an unquoted <right-curly-bracket> ('}')
may be subject to an additional implementation-defined form
of expansion that can create multiple fields from a single
word. This expansion, if supported, shall be applied before
all the other word expansions are applied. The other
expansions shall then be applied to each field that results
from this expansion.
https://pubs.opengroup.org/onlinepubs/9799919799.2024edition/utilities/V3_chap02.html#tag_19_06
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vq
