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

[Lawrence Velázquez <larryv@xxxxxxxxxxxx>]

On Jul 1, 2013, at 8:58 PM, TJ Luoma <luomat@xxxxxxxxx> 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'
> 
> % echo "foo\nbar\nbat" | egrep -v '[F|f]'
> bar
> bat
> 
> % echo "foo\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
> XXX
> bar
> bat

These regex are not matching what you think they are matching. For sure, "[F|f]" matches both lowercase and uppercase F, but as ZyX said, it also matches pipe characters:

    % echo "foo\nbar\nbaz\nbar|||baz" | egrep -v '[F|f]'
    bar
    baz

    % echo "foo\nbar\nbaz\nbar|||baz" | sed 's/[F|f][O|o][O|o]/XXX/g'
    XXX
    bar
    baz
    barXXXbaz

You are probably thinking of "(F|f)"; you should just use "[Ff]".

> 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

Same misconception here; pipes in patterns' bracket expressions have no special meaning. You can remove all the pipes from your example, and it would still work.

    % case "crasHPLan" in
    case>           [Cc][Rr][Aa][Ss][Hh][Pp][Ll][Aa][Nn]) echo "matched";;
    case>           *) echo "did not match";;
    case> esac
    matched

vq