[Bug 195763] bsdgrep, empty matches and -o

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=195763

Kyle Evans <bsdports at kyle-evans.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bsdports at kyle-evans.net

--- Comment #1 from Kyle Evans <bsdports at kyle-evans.net> ---
Created attachment 179126
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=179126&action=edit
Proposed patch to address zero length match issues with bsdgrep

Hi,

Attached is a patch that seems to fix the behavior of zero-length matches.
procline() was previously using something along the lines of 'next start (st)
== match start' to indicate failure, but this isn't right when zero-length
matches are possible. Therefore, we make a couple of critical changes:

1.) Keep track of the number of total matches we came across
2.) Don't add zero-length matches to our output
3.) If we had any matches, keep going. If st didn't advance beyond our first
match, we only had zero-length matches

To fix the empty expression case, I changed the argv pattern matching bits in
main() to actually skip invalid expressions. 

Your test expressions now yield the following results:
root at ghost:/usr/obj/usr/src/usr.bin/grep# echo '01:1:01' | ./bsdgrep -Eo
'(^|:)0*'
0
:
:0
# Good
root at ghost:/usr/obj/usr/src/usr.bin/grep# echo '1:1:01' | ./bsdgrep -Eo
'(^|:)0*'
:
:0
# Better
root at ghost:/usr/obj/usr/src/usr.bin/grep# echo 'bla bla' | ./bsdgrep -Eo
'[[:alnum:]]*'
bla
bla
# Good
root at ghost:/usr/obj/usr/src/usr.bin/grep# printf 'bla\nbla\n' | ./bsdgrep -Eo
''
# Good

I think this approach is mostly right, except for perhaps the bits in
grep.c:main() to make sure we don't recognize invalid patterns as input
patterns.

-- 
You are receiving this mail because:
You are the assignee for the bug.