Re: Regex Question

The easiest way to fix this substitution is to capture the extra characters: s/([^\n])\n([^\n])/$1$2/g; Although negative lookahead and/or lookbehind could be used instead: s/(?<!\n)\n(?!\n)//g; Lookahead and lookbehind assertions make sure that the subpattern matches (or doesn't match, for negative assertions), without using up those characters in the actual match. perlre explains it better. :)

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Re: Re: Regex Question by merlyn (Sage) on Jan 08, 2001 at 00:02 UTC
`s/([^\n])\n([^\n])/$1$2/g;` That fails on `fred\nX\nY\nbarney`, since the X will be sucked up while fixing the preceding newline, and won't be available to match for the following newline. Be very wary when matching right-side context. Passing it through to the "already seen" category means it won't be able to be left-side context for a later match. -- Randal L. Schwartz, Perl hacker	[reply] [d/l]
Re (tilly) 3: Regex Question by tilly (Archbishop) on Jan 08, 2001 at 00:11 UTC
That is fixable though with a lookahead: `s/([^\n])\n(?!\n)/$1/g;` [download] Or the probably faster lookbehind: `s/(?<!\n)\n([^\n])/$1/g;` [download] UPDATE chipmunk noticed a typo. I had not closed the second match. Oops.	[reply] [d/l] [select]