Zachary Santer <zsan...@gmail.com> writes:
> Description:
> Similarly, history expansion occurs within arithmetic substitutions. This
> will never, ever be what the user wants. And now I know how to make it not
> happen.
>
> Repeat-By:
> $ set +o histexpand
Well, yes, if you turn off history expansion, then it won't occur within
arithmetic substitutions.
But I would not take it as given that nobody would ever want to use
history expanstion within an arithmetic substitution. Let me concoct an
example:
$ i=4
$ echo (( i+1 ))
bash: syntax error near unexpected token `('
$ echo $(( !:3 ))
echo $(( i+1 ))
5
$
(This would be more likely if "i+1" was a much more complicated
expression.)
But it seems to me that the way to avoid this is to always put a space
after "!" in arithmetic expressions. "!" followed by space is never
subject to history expansion.
More troublesome, I think, are several variable substitutions which
include "!" followed by a name. But I doubt they're used much in
interactive mode.
Dale
