On 27/05/2012, at 17:39, Geir Hauge <geir.ha...@gmail.com> wrote: > 2012/5/27 Jon Seymour <jon.seym...@gmail.com>: >> Is there a reason why bash doesn't treat == as an illegal test >> operator when running in POSIX mode? > > POSIX does not say == is not allowed. > > POSIX tells you what the shell should at least be able to do. A POSIX > compliant shell can have whatever other features it likes, as long as > the POSIX features are covered. >
I guess the question is better phrased thus: what use case is usefully served by having bash's POSIX mode support a superset of test operators than other compliant POSIX shells? As it stands, I can't use bash's POSIX mode to verify the validity or otherwise of a POSIX script because bash won't report these kinds of errors - even when running in POSIX mode. There is an --enable-strict-posix (?) configuration option. Will this do what I expect? > >> This is problematic because use of test == in scripts that should be >> POSIX isn't getting caught when I run them under bash's POSIX mode. >> The scripts then fail when run under dash which seems to be stricter >> about this. > > Don't use non-POSIX features in a POSIX script, and you'll be fine. > http://www.opengroup.org/onlinepubs/9699919799/utilities/contents.html > Which is the exactly the point. Practically speaking when I write scripts I expect an interpreter that claims to be running in POSIX mode to give me some help to flag usage of non POSIX idioms. Yes, I can second guess the interpreter by reading the spec, but is this really the most efficient way to catch these kinds of errors? Jon.
