[conspire] Basic Regular Expressions (GNU/Linux "vs." BSD)

[Ivan Sergio Borgonovo]

Is there an -E option on BSD?
or did you try to use --posix on Linux?

On 2/18/21 10:17, Michael Paoli wrote:
> Ah, drats ... I'd expect I ought get the same from both of these, ...
> but no.  Not quite sure if I'm not interpreting things exactly right,
> or there's sufficient wiggle room with BRE on this in POSIX, or there
> might possibly actually be a bug in the BSD case on this.
> But, with both grep and sed, seeing quite different results on these,
> notably BRE not matching, as in fact expected, yet on BSD matching
> where not expecting it to match:
> 
> GNU/Linux:
> $ echo 'xxo o x  ' | sed -ne 
> '/^\(...\)\{0,2\}\([ox]\)\2\2/{s/.*/matched/p;}'
> $ echo 'xxo o x  ' | grep -e '^\(...\)\{0,2\}\([ox]\)\2\2'
> $ echo 'xxo o x  ' | sed -ne 's/^\(...\)\{0,2\}\([ox]\)\2\2/1:\12:\2\&:&/p'
> $
> 
> BSD:
> $ echo 'xxo o x  ' | sed -ne 
> '/^\(...\)\{0,2\}\([ox]\)\2\2/{s/.*/matched/p;}'
> matched
> $ echo 'xxo o x  ' | grep -e '^\(...\)\{0,2\}\([ox]\)\2\2'
> xxo o x
> $ echo 'xxo o x  ' | sed -ne 's/^\(...\)\{0,2\}\([ox]\)\2\2/1:\12:\2\&:&/p'
> 1:xxo2:&:xxo o x
> $
> 
> How can \([xo]\) matching zero characters be correct?
> That seems broken to me.
> 
> But these work the same on both, as expected:
> $ echo 'xox' | grep '^\([xo]\)\1\1$'
> $ echo 'xxx' | grep '^\([xo]\)\1\1$'
> xxx
> $ echo 'xox' | sed -ne '/^\([xo]\)\1\1$/p'
> $ echo 'xxx' | sed -ne '/^\([xo]\)\1\1$/p'
> xxx
> $
> 
> 
> _______________________________________________
> conspire mailing list
> conspire at linuxmafia.com
> http://linuxmafia.com/mailman/listinfo/conspire

-- 
Ivan Sergio Borgonovo
https://www.webthatworks.it https://www.borgonovo.net