Re: [patch #10070] toggle invert flag when reading `!'

[Martijn Dekker]

Op 24-05-21 om 17:47 schreef Chet Ramey:
> On 5/22/21 2:45 PM, Vincent Menegaux wrote:
> > Previously, these commands:
> >
> >    [[ ! 1 -eq 1 ]]; echo $?
> >    [[ ! ! 1 -eq 1 ]]; echo $?
> >
> > would both result in `1', since parsing `!' set CMD_INVERT_RETURN
> > instead of toggling it.
>
> Interestingly, ksh93 produces the same result as bash. I agree that it's
> more intuitive to toggle it.


Also interesting is that '!' as an argument to the simple 'test'/'[' 
command does work as expected (on both bash and ksh93): 'test ! ! 1 -eq 
1' and '[ ! ! 1 -eq 1 ]' return 0/true.

Even the man page for [[ is identical for bash and ksh93:

|               ! expression
|                      True if expression is false.

This suggests it's supposed to be a logical negation operator, i.e. '!' 
is implicitly documented to negate another '!'. Bolsky & Korn's 1995 ksh 
book, p. 167, is slightly more explicit about it: "! test-expression. 
Logical negation of test-expression."

I also note that multiple '!' negators in '[[' work as expected on mksh, 
yash and zsh.

So, it seems clear that this is an actual bug in bash and ksh. I see 
it's been fixed in the bash devel tree now. I'll fix it in ksh 93u+m.

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