Regexp to match only n occurrences of a char in a string

Question

I have a string like 2005:10:29 12:23:53 and I wish to replace only first two occurrences of : with -

Expected result 2005-10-29 12:23:53

EDIT:

I need this regexp in KDE's krename tool, where I can't edit/format the original [exifExif.Image.DateTime] witch returns the unwanted 2005:10:29 12:23:53 format, but there is a Find and Replace to post process the String

(?<=\d{4}):|:(?=\d{2}\s) does the job on rubular, but does not in KDE :(

I am sure there are more solutions.

EDIT:

:(?=\d{2}:\d{2}\s)|:(?=\d{2}\s) works even on KDE

I find this solution after I read

You can use a full-fledged regular expression inside the lookahead.
Most regular expression engines only allow literal characters and
alternation inside lookbehind, since they cannot apply regular
expression backwards.

in Regex tutorial

so what language do you want to use? You just removed JavaScript and Ruby... — mplungjan, Mar 22 '12 at 10:24
I think you'd better ask krename support: http://www.krename.net/Mailinglist.14.0.html — Toto, Mar 22 '12 at 11:05

score 3 · Answer 1 · answered Mar 22 '12 at 10:17

3

In Ruby, as scibuff suggests, you're probably better not using Regexps.

require 'date'
date = DateTime.parse("2005:10:29 12:23:53", "%Y:%m:%d %H:%M:%S")
date.strftime("%Y-%m-%d %H:%M:%S")

answered Mar 22 '12 at 10:17

Chowlett

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Sorry for confusing tags I removed them (javascript, ruby) +1 for ruby solution. – kfl62 Mar 22 '12 at 10:24

mplungjan · Answer 2 · 2012-03-22T10:20:34.060

1

JavaScript:

Version 1

str = str.split(' ')[0].replace(/\:/g,'-')+' '+str.split(' ')[1]

Version 2

str = str.replace(/(\d{4}):(\d{2}):(\d{2})(.*)/,"$1-$2-$3 $4")

DEMO

edited Mar 22 '12 at 10:20

answered Mar 22 '12 at 10:08

mplungjan

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Sorry for confusing tags I removed them (javascript, ruby) – kfl62 Mar 22 '12 at 10:24
+1 works fine in JavaScript and nice to know about DEMO link :) – kfl62 Mar 22 '12 at 18:23

score -1 · Answer 3 · answered Mar 22 '12 at 10:09

-1

Once again using regular expressions for something that can be achieved in a simpler, more elegant and more efficient way

var date = new Date('2005:10:29 12:23:53');

then format date accordingly, e.g.

function formatDate( date ){

    return date.getFullYear() + '-' + ( get.getMonth() + 1 ) + '-' + ... ;

}

answered Mar 22 '12 at 10:09

scibuff

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That would be wonderful if the Date function allowed yyyy:mm:dd hh:mm:ss - but it doesn't. So you need to first change the first set of : to - which is what OP wanted to know how to do – mplungjan Mar 22 '12 at 10:19
Sorry for confusing tags I removed them (javascript, ruby) – kfl62 Mar 22 '12 at 10:23

score -1 · Answer 4 · answered Mar 22 '12 at 10:30

-1

Simply call replace() twice:

"2005:10:29 12:23:53".replace(/:/,'-').replace(/:/,'-')

answered Mar 22 '12 at 10:30

codef0rmer

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Regexp to match only n occurrences of a char in a string

4 Answers4