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    Regex: Select only the first instance of search results / first match

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    • Vasile CarausV
      Vasile Caraus @Alan Kilborn
      last edited by

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      • Vasile CarausV
        Vasile Caraus @Alan Kilborn
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        • Vasile CarausV
          Vasile Caraus
          last edited by

          so, conclusion. I select all regex from the las converstion:

          Select and replace the first instance:

          SEARCH: (?s)\A.*?<tr>\s*\K.*?(\s*</tr>)(?=$)
          REPLACE BY: NEW CONTENT $1

          or

          SEARCH: (?s)\A.*?<tr>\s*\K.*?(\s*</tr>)
          REPLACE BY: NEW CONTENT $1

          Select and replace the last instance:

          SEARCH: (?s)<tr>.*</tr>.*?<tr>\K.+?(?=</tr>.*?\z)
          REPLACE BY: \r NEW CONTENS $1 \r

          or

          SEARCH: (?s)\A.*<tr>\K.+?(?=</tr>)
          REPLACE BY: \r NEW CONTENS $1 \r

          WORKS. Thanks a lot friends.

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          • Alan KilbornA
            Alan Kilborn
            last edited by Alan Kilborn

            This all seems rather “special case”.
            This <tr> and </tr> junk…

            To be generic, that is, a roadmap for other interested parties to use, why not specify it like this:


            Match only the first occurrence in a file of a regular expression RE:

            (?s)\A.*?\KRE


            Match the last occurrence of a regular expression RE:

            (?s)\A.*(RE).*?\K\1


            Of course, clearly the RE has to be something a bit more specific than (example) .., but these seem to mostly work to achieve the goal.

            1 Reply Last reply Reply Quote 2
            • guy038G
              guy038
              last edited by guy038

              Hello, @vasile-caraus, @Terry-R, @alan-kilborn, @peterjones and All,

              IMPORTANT : I wrote this post, after reading posts from the banner 4 YEARS LATER till the @peterjones’s post, below :

              https://community.notepad-plus-plus.org/post/62964

              But I going to add a second post, after reading the last recent solutions ! Sorry for my incomplete work !


              First, @vasile-caraus, I totally agree to @alan-kilbron’s comment on your attitude ! Not very fair and nice to @Terry-r, which was trying to help you :-((

              Seemingly, you quite know, by now, the powerful of regexes, regarding text manipulations. And if you had studied, seriously, some regex tutorials, you would not have spoken about that regex (?s)\z.*?<tr>\s*\K.*?(\s*</tr>) which is a complete nonsense !

              For instance, from the two pages of the Regular-expressions.info site, below, you had understood, at once, that the \z syntax always comes at the very end of a regex expression or, possibly, before an alternation symbol | !!

              https://www.regular-expressions.info/anchors.html

              https://www.regular-expressions.info/refanchors.html


              Now, I slightly simplified the @peterjones’s search regex, which searches for the first element <tr> ••••• </tr>, of an HTML page :

              SEARCH (?s-i)\A.*?<tr>\K.*?(?=</tr>)

              In return, if your replacement regex is :

              • The expression Here is the NEW text, you’ll get the simple text
               </tr>Here is the NEW text</tr>
              
              • The expression is \r\nHere is the NEW text\r\n the output text will be :
              <tr>
              Here is the NEW text
              </tr>
              
              • Tick the Wrap around option

              • Click on the Replace All button, exclusively !


              Now, to search for the last element <tr> ••••• </tr>, of an HTML page, use the following regex :

              SEARCH (?s-i)<tr>\K((?!<tr>).)*?(?=</tr>((?!<tr>).)*?\z)

              Note that I use exactly the scheme proposed by @Peterjones :

              
              - find from <tr> to </tr> ( NOT included )          =>    (?s-i)<tr>\K •••••••••• (?=</tr> •••••••••• )
                                                                                         ^                 ^    ^
                                                                                         |                 |    |
              - WITHOUT any contained <tr>                        =>    ((?!<tr>).)*? ---•                 |    |
              																							 |    |
              - FOLLOWED by anything that’s NOT a <tr>            =>    ((?!<tr>).)*? ---------------------•    |
              																								  |
              - until the VERY END of the file                    =>    \z -------------------------------------•
              

              To All :

              You could ask me : why the regex to search for the last <tr> ••••• </tr> block is more complicated than the one to search for the first one ?

              This is because of the general direction used by the regex engine : from LEFT to RIGHT !

              • Indeed, when we search for (?s-i)\A.*?<tr>, part of the first regex, the range of any char (?s).* with the lazy quantifier ? is then extended to the first occurrence of the string <tr> and means that, necessarily, this range cannot contain any <tr> inside !

              • Similarly, the regex (?s).*?(?=</tr>) would search for any range of any char, possibly empty, till the nearest string </tr>, meaning, implicitly, that this range of chars cannot contain a </tr> string

              • Whereas, when searching the last <tr> ••••• </tr> block, as our reference is the anchor \z ( very end of current file ), we must build up the regex, using a kind of back-propagation method :

                • Starting from the very end of file

                • Moving back, through characters without any <tr> string

                • Till a </tr> string

                • Moving back, again, through characters without any <tr> string

                • Till a <tr> string

              Of course, I assume that any <tr> correctly ends with </tr> !

              Test these two regexes against this sample, derived from Peter’s one, which contains 4 blocks </tr> •••• </tr> :

              <html><body>
              <table>
              <tr>
              get rid of stuff, in case of \A anchor, including <embedded/> <tags/>
              </tr>
              <tr>
              keep stuff including <embedded/> <tags/>
              </tr>
              <tr>
              keep stuff including <embedded/> <tags/>
              </tr>
              <tr>
              get rid of stuff, in case of \z anchor, including <embedded/> <tags/>
              </tr>
              </table>
              </body>
              </html>
              

              The first regex, with the \A syntax should replace the first block, only and the last regex, with the \z syntax, should replace the fourth and last <tr> block

              Best Regards,

              guy038

              P.S. :

              @vasile-caraus, note that I’m willing, and probably, all people involved in that discussion, to help you if you have difficulty understanding a specific part of a regex tutorial, that you have decided to study. A different perspective will certainly be very useful to you … and others ;-))

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              • guy038G
                guy038
                last edited by

                Hi, @vasile-caraus, @Terry-R, @alan-kilborn, @peterjones and All,

                My God !! Of course, the @terry-r’s regex is just magic and so simple ! Congratulations, Terry ;-)) How could we not think of it ??

                If I adapt Terry concept to the regexes of my previous post, everything becomes crystal clear :

                SEARCH (?s-i)\A.*?<tr>\K.*?(?=</tr>) to search ( and replace ) the first <tr> ••••• </tr> block

                SEARCH (?s-i)\A.*<tr>\K.*?(?=</tr>) to search ( and replace ) the last <tr> ••••• </tr> block

                As usual, tick the Regular expression and Wrap around options and click on the Replace All button, exclusively


                @vasile-caraus, this demonstrates, in a masterful way, that things can be skillfully solved by other people than me and moreover… by @terry-r !!


                Now, @alan-kilborn you said :

                Match the last occurrence of a regular expression RE:

                (?s)\A.*(RE).*?\K\1

                But, unless I’m mistaken, doesn’t this regex, below, do the same search ?

                (?s)\A.*\KRE

                Best regards,

                guy038

                Alan KilbornA Vasile CarausV 2 Replies Last reply Reply Quote 2
                • Terry RT
                  Terry R
                  last edited by Terry R

                  @guy038 said in Regex: Select only the first instance of search results / first match:

                  Hi, @vasile-caraus, @Terry-R, @alan-kilborn, @peterjones and All,
                  My God !! Of course, the @terry-r’s regex is just magic and so simple !

                  I feel like I’m being rewarded for something I stole borrowed now. ;-)) All I did was point out the marvellous creation of @PeterJones and how by the absence of a single character it turns one thing into another.

                  But hey, I’m happy that collectively we can show there are many answers, all work in various ways.

                  Terry

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                  • Alan KilbornA
                    Alan Kilborn @guy038
                    last edited by

                    @guy038 said in Regex: Select only the first instance of search results / first match:

                    But, unless I’m mistaken, doesn’t this regex, below, do the same search ?
                    (?s)\A.*\KRE

                    Yes, indeed.
                    That’s what I get for dabbling in the area of another master! :-)

                    1 Reply Last reply Reply Quote 1
                    • Vasile CarausV
                      Vasile Caraus @guy038
                      last edited by

                      @guy038 thanks a lot !

                      dr ramaanandD 1 Reply Last reply Reply Quote 0
                      • dr ramaanandD
                        dr ramaanand @Vasile Caraus
                        last edited by dr ramaanand

                        @Vasile-Caraus The regular expression (?s)\A.*?\Kstring(?:.*?)?> helps find the very first occurrence of a string and if you want to find the first occurrence of a tag, say TAG_2, AFTER the first occurrence of another tag, say TAG_1, my generic regex becomes :

                        (?s-i)\A.*?<TAG_1(?: .*?)?>.*?\K<TAG_2(?: .*?)?> as per @guy038

                        dr ramaanandD 1 Reply Last reply Reply Quote 0
                        • dr ramaanandD
                          dr ramaanand @dr ramaanand
                          last edited by dr ramaanand

                          On testing the above, I observed that both the above regular expressions work only for tags or strings that begin with a < and end with a > - so if you are searching for a string between inverted commas, to find the first string, you should use the regular expression (?s)\A.*?\K"string(?:.*?)?"

                          dr ramaanandD 1 Reply Last reply Reply Quote 0
                          • dr ramaanandD
                            dr ramaanand @dr ramaanand
                            last edited by dr ramaanand

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