Axel Liljencrantz wrote:
Of, I have added a patch to the Darcs version of fish which changes the
syntax of 'and' and 'or' to:
[infix semantics, as builtins - the previous command must be properly
terminated]
You will notice in the above example that 'pwd && whoami' actually
launches 'pwd &' in the background. Maybe fish should do a syntax check
on the whole commandline and reject all of it instead?
After installing the most recent darcs repo fish build I think that the
error message redirecting the user to "or" or "and" is great for
discoverability for migrating POSIX scripters. I think it's best not to
run the job in the background though - it's almost certainly not what
the user intended.
But then, if you're going to be doing that parsing anyway, why not
simply do the replacement on behalf of the user:
"||" becomes "; or "
"&&" becomes "; and "
OK, I already know your answer - "one syntax only", "ugly hack", etc. ;-)
But this does give me another idea - let's assume Joe User wants to
implement this alias. Fish doesn't support functions with pipe symbols
in their name, and the symbol doesn't occur in a valid spot for a
function anyhow, so that's out of the question.
How about supporting it through the (evolving) event model though: there
could be a "parser error" event, and one particular error could have
type "double-pipe". The user could install a handler for the
double-pipe parser error, and this handler would be given enough
information to be able to replace the double-pipe in the command-line
with "; or ". A little esoteric, but perhaps less objectionable to your
no-configurability tastes.
Even more generically, there could be a pre-parse-commandline event that
would do replacements prior to fish interpreting the commandline.
Things like that would help to make a POSIX-compatible mode for fish a
possibility (activated through an entry-point function in a set of
separately distributed fish functions) without disturbing your desire to
avoid configurable options. It wouldn't be expected that users enable
this mode by default, but it would be helpful if they e.g. want to run a
POSIX script without changing shells, or want to try fish out briefly to
investigate its usability features without having to learn its syntax
when they already know POSIX.
--
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