Re: input foo, output '[F|f][O|o][O|o]'?

["Benjamin R. Haskell" <zsh@benizi.com>]

On Mon, 1 Jul 2013, TJ Luoma wrote:

>
> On 1 Jul 2013, at 14:44, ZyX wrote:
>
>> [...]
>> By the way, what regex engine is your output for? Any I am aware of 
>> parse "[N|n]" as "either one of three characters: N, n, or pipe".
>
> Really? I can think of several that support it. Maybe it's because I'm old 
> enough to remember when a lot of these utilities didn't have 'ignore case'

I think you've missed the point of "N, n, or pipe".  [F|f] matches upper 
'F' or lower 'f', but also the character '|'.  You seem to be 
conflating:

[xyz] - 'x' or 'y' or 'z'

with:

(x|y|z) - 'x' or 'y' or 'z'

The '|' doesn't mean 'or' within square brackets.  It means the literal 
character: '|'.


> % echo "foo\nbar\nbat" | egrep -v '[F|f]'
> bar
> bat

% echo "foo\nb|r\nbat" | egrep -v '[F|f]'
bat
(It rejected 'b|r', because it contains '|', even though it doesn't 
contain 'F' or 'f')


> % echo "foo\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
> XXX
> bar
> bat

% echo "f|o\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
XXX
bar
bat
(It changed 'f|o' to 'XXX', despite '|' not being 'O' or 'o')


> You can also use it for matching case/esac :
>
> case "$i" in
> 	[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n])
> 			echo "matched crashplan"
> 	;;
>
> 	*)
> 			echo "No Match"
> 	;;
>
> esac

(Using a smaller example:)

i='|||'

case "$i" in
   [F|f][O|o][O|o]) echo matched foo ;;
   *) echo no match ;;
esac

will echo:
matched foo

You really just want:

[Cc][Rr][Aa][Ss][Hh][Pp][Ll][Aa][Nn])