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Re: How do I do this search and replace? [message #172351 is a reply to message #172347]

Mon, 14 February 2011 09:55

The Natural Philosoph
Messages: 993
Registered: September 2010

Karma:

Senior Member

Erwin Moller wrote:
> On 2/12/2011 11:51 PM, BootNic wrote:
>> On Sat, 12 Feb 2011 13:15:44 -0800 (PST)
>> "laredotornado(at)zipmail(dot)com"<laredotornado(at)zipmail(dot)com> wrote:
>>
>>> I'm using PHP 5. I want to search for all instances of the "\n"
>>> character in my $contents variable and replace it with "\r\n".
>>> However, I do not want to replace the "\n" if the character
>>> immediately before is already a "\r". How would I construct such
>>> a search and replace to do this?
>>
>> http://www.regular-expressions.info/lookaround.html#lookbehind
>>
>>
>> using negative lookbehind
>>
>> $contents = preg_replace("/(?<!\r)\n/", "\r\n", $contents);
>>
>>
>
> One addition: Using the double replacement strategy as described by
> Richard is easier to understand (for non-regexp people), but needs 2
> sweeps over the content.
>
> In case performance matters (more specifically: if the $contents is a
> huge string, or/and you have to do this replacement many times
> sequentially), if might be better to use the above approach from
> BootNic, because I expect it will be much faster.
>

If performance is an issue, code a one pass loop. Preferably in
assembler :-)

regexp processing is not fast.

> If performance isn't an issue, pick whatever suits you. :-)
>
> Regards,
> Erwin Moller
>

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[Message index]

		How do I do this search and replace? By: laredotornado@zipmail on Sat, 12 February 2011 21:15
		Re: How do I do this search and replace? By: richard on Sat, 12 February 2011 21:20
		Re: How do I do this search and replace? By: Evan Platt on Sat, 12 February 2011 22:09
		Re: How do I do this search and replace? By: sheldonlg on Sat, 12 February 2011 23:59
		Re: How do I do this search and replace? By: Tim Streater on Sun, 13 February 2011 00:08
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 00:24
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 00:40
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 01:03
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 00:58
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 00:57
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 01:14
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 01:23
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 01:29
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 01:38
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 01:54
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:00
		Re: How do I do this search and replace? By: spambait on Sun, 13 February 2011 13:16
		Re: How do I do this search and replace? By: The Natural Philosoph on Sun, 13 February 2011 13:33
		Re: How do I do this search and replace? By: me on Sun, 13 February 2011 13:45
		Re: How do I do this search and replace? By: sheldonlg on Sun, 13 February 2011 13:48
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 13:51
		Re: How do I do this search and replace? By: spambait on Mon, 14 February 2011 01:58
		Re: How do I do this search and replace? By: Denis McMahon on Mon, 14 February 2011 02:25
		Re: How do I do this search and replace? By: The Natural Philosoph on Mon, 14 February 2011 09:51
		Re: How do I do this search and replace? By: sheldonlg on Mon, 14 February 2011 12:50
		Re: How do I do this search and replace? By: Jerry Stuckle on Mon, 14 February 2011 12:58
		Re: How do I do this search and replace? By: Denis McMahon on Mon, 14 February 2011 15:34
		Re: How do I do this search and replace? By: Jerry Stuckle on Mon, 14 February 2011 17:57
		Re: How do I do this search and replace? By: spambait on Sun, 13 February 2011 01:48
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:01
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 02:05
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:13
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 02:33
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:44
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 02:49
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:53
		Re: How do I do this search and replace? By: me on Sun, 13 February 2011 13:32
		Re: How do I do this search and replace? By: The Natural Philosoph on Sun, 13 February 2011 13:37
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 13:53
		Re: How do I do this search and replace? By: Denis McMahon on Sun, 13 February 2011 04:16
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 04:34
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 04:50
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 05:35
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 06:11
		Re: How do I do this search and replace? By: sheldonlg on Sun, 13 February 2011 13:19
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 13:56
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 15:09
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 15:19
		Re: How do I do this search and replace? By: Denis McMahon on Sat, 12 February 2011 22:03
		Re: How do I do this search and replace? By: BootNic on Sat, 12 February 2011 22:51
		Re: How do I do this search and replace? By: The Natural Philosoph on Sun, 13 February 2011 00:21
		Re: How do I do this search and replace? By: Curtis Dyer on Mon, 14 February 2011 09:01
		Re: How do I do this search and replace? By: The Natural Philosoph on Mon, 14 February 2011 09:54
		Re: How do I do this search and replace? By: Erwin Moller on Mon, 14 February 2011 09:14
		Re: How do I do this search and replace? By: The Natural Philosoph on Mon, 14 February 2011 09:55
		Re: How do I do this search and replace? By: Erwin Moller on Mon, 14 February 2011 10:04
		Re: How do I do this search and replace? By: The Natural Philosoph on Mon, 14 February 2011 10:28
		Re: How do I do this search and replace? By: Curtis Dyer on Mon, 14 February 2011 10:40

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