echo `x[~a]` echos `x` and `xb`

[borkovic]

rc

I was trying to collect all files/dirs with 2 character names starting with a dot (.) in the current directory, except for the parent dir (..).

Skip double dot

The following did not quite work:

; la
./	../	.j	.k	j	j.c
; echo ./.?      # echo 1
./.. ./.j ./.k
; echo ./.[~.]   # echo 2
./. ./.j ./.k
; echo .?      # echo 3
.. .j .k
; echo .[~.]   # echo 4
. .j .k

In echos 2 and 4 ./.. and.. did not appear as expected, but I did not expect to see the current dir (./. and .).

Was my expectation correct?

Dot in the second place is not special

Also tried pattern .[~j]. Single dot is shown here as well.

; echo .[~j]
. .. .k

Dot in the first place is not special either

Dot is not special:

; touch x xa xb
; echo x[~a]
x xb

bash

In bash single dot is not echoed.

$ echo .[!.]
.j .k
$ echo .[^.]
.j .k

[rakitzis]

Strange, I cannot repro on my mac:

; touch .x
; echo .?
.. .x
; echo .[~.]
.x
; echo ./.[~.]
./.x

[rakitzis]

Using your test data literally:

; touch .j .k j j.c
; echo .[~.]
.j .k

What build of rc is this?

[jpco]

I get the same buggy behavior as originally posted, on v1.7.4-193-g27ed71e. When matching was refactored in commit 35e4210, it looks like an explicit ``` if (*s == '\0') return FALSE; ``` check was deleted.

[rakitzis]

Thanks, great catch. I'll investigate a fix, it would be nice to keep the linear time scan if possible.

[borkovic]

Another difference between rc and bash. I would not classify this as a bug. Both rc and bash man page state that ? matches any character, and it seems that rc is truer to its man page.

$ rc
; echo .?
.. .j .k
; exit
$ echo .?
.j .k

[rakitzis]

Yeah, I don't think that's it. m is an array of bits (0, 1) which indicate whether the underlying character is special or not (*, ?, etc.) -- this keeps the strings 8-bit clean.

[rakitzis]

Aha, the fix you made looks like it addresses the underlying cause. I wonder if there is a way to fuzz test this pattern matcher.