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



  • hello. I have a html bug. And I have to change it in more then 2000 files.

    I need to replace only the first instance of a search result.

    For example, I have this line <div class=“pagination”> . The problem is that this line is repeated 5 times in each html file. So, if I want to search and replace this line, I risk to delete all other same lines.

    My search should stop of first match.

    I made a little regex, but does’t work for me.

    ^.*(<div class="pagination">)((?s:)).*/

    Can anyone help me, please?



  • Hello Vasile,

    I’ve got a solution, based on the one I gave in my last post, on the topic : Regex : Double your words, below, where I also matched all the remaining contents of the file, in order to be certain that will be ONE replacement, only, per file !

    https://notepad-plus-plus.org/community/topic/12341/regex-double-your-words/9

    I, also, supposed, Vasile, that the line, containing your string <div class=“pagination”>, may have some characters before and/or after that specific string.

    Well, Let’s go !

    • To change the contents of the FIRST line, ONLY, of the current file, which contains the string <div class=“pagination”>, use :

    SEARCH : (?-s)(?:.*\R)*?\K.*<div class=“pagination”>.*(?s)(\R.*)

    REPLACE : New contents of the line\1

    • To change the contents of the LAST line, ONLY, of the current file, which contains the string <div class=“pagination”>, use :

    SEARCH : (?-s)(?:.*\R)*\K.*<div class=“pagination”>.*(?s)(\R.*)

    REPLACE : New contents of the line\1

    ***** With the help of Vasile, see, below, in my next post, a shorter version of these two regexes ! *****


    Notes :

    • I won’t speak about the (?-s) and (?s) in-line modifiers ! You already aware about their use :-)

    • The first part (?:.*\R)*? catches the minimum number of complete lines, before the line containing the string <div class=“pagination”>

    • Then, again, the \K syntax forces the regex engine to forget the present match and reset the cursor location just before the first character of the line to be changed

    • Then the next part .*<div class=“pagination”>.* corresponds to all the standard characters of the line to be changed

    • And the final part (\R.*) stands for the EOL character(s) of the line to be changed, followed by all the text, till the end of the current file

    • In the second S/R, the first part (?:.*\R)* catches the maximum number of complete lines, before the line containing the string <div class=“pagination”>

    • In replacement, we just changed the contents of line, containing the string <div class=“pagination”>, by the string New contents of the line, followed by the contents of group 1 ( = text from the next line to the end of the current file )


    IMPORTANT :

    As usual, if you perform these S/R, on a few files, using the Replace dialog ( CTRL + H ), just remember these two rules :

    • Firstly, go to the very beginning of the current file ( CTRL + Origin )

    • Secondly use, exclusively, the Replace All button ( Due to the \K syntax, the step by step replacement, with the Replace button, does NOT work ! )

    Cheers,

    guy038

    P.S. :

    Of course, if the Find/Replace dialog would contain the four, non standard, options :

    • Skip the first N matches

    • Find/Replace the next M matches, only

    • Per Line : [X] or Per File : [X]

    Vasile, you just would have to type 0 for number N, 1 for number M and check the Per File option.

    Then, this simple following S/R would be enough !

    SEARCH : (?-s).*<div class=“pagination”>.*

    REPLACE : New contents of the line



  • hello guy, I must say you have always something great to say about regex. You helped me a lot !

    about the first part, the two regex works fine.

    But, I don’t really understand the last part (P.S. :) the four, non standard, options

    I cannot see the

    I guess, something is missing on my part. Can u give me a print screen?



  • I found on internet a more simple way

    Step1. Enable the . matches newline option

    Search
    <div class=“pagination”>(.*)\z
    Replace by:
    Anything $1



  • Hi, Vasile,

    Two points :

    • Firstly, Vasile, don’t be mistaken about what I wrote, at the end of my previous post ! I was just dreaming about it ! Of course, these options are NOT part of the presentFind/Replace” dialog. And they, probably, will NEVER be :-((

    I just wanted to point out that these additional options could help us, in some cases, to build more simple regexes !


    • Secondly, yes, you’re right : your regex is more elegant ! But it works ONLY IF there is ONE string <div class=“pagination”>, exactly, in your current file. And seemingly, you said :

    The problem is that this line is repeated 5 times in each html file

    But, indeed, it’s incredible how our brain is disposed to make simple things more complicated:-(( So, from your interesting regex, we can, still, simplify the previous regexes :


    • To change the contents of the FIRST line, ONLY, of the current file, containing the string <div class=“pagination”>, use :

    SEARCH : (?s)<div class=“pagination”>(.*)

    REPLACE : Anything else\1

    • To change the contents of the LAST line, ONLY, of the current file, containing the string <div class=“pagination”>, use :

    SEARCH : (?s).*\K<div class=“pagination”>(.*)

    REPLACE : Anything else\1


    I don’t think we’ll be able to get shorter regexes !!

    Notes :

    • As usual, the in-line modifier (?s) prevent us to mind about checking/unchecking the .matches newline option

    • In the second regex, we need to add, at the beginning, the form .*\K, in order to get the maximum range of characters till the last string <div class=“pagination”>, of the current file

    • The last part of the regex (.*) represents the remaining text, after the matched string <div class=“pagination”>, till the very end of file

    Cheers,

    guy038



  • hello guy, works wonderful. Thank you.

    But one more thing, I cannot get the solution. At the regex below, as you can see, first part I select all before a word. And part two select all after a word. Practicaly, I select a middle text from a file. Works beautiful. I use Replace All for more then 2000 files.

    (?s)((^.*)(DELETE_UNTIL_THIS_TEXT)|(DELETE_AFTER_THIS_TEXT)(.*$))

    Sometimes, the problem is when I have more instances at the last part. For exemple:

    text_1
    DELETE_UNTIL_THIS_TEXT (text_1)
    –my text–
    –my text–
    DELETE_AFTER_THIS_TEXT (text_2)
    text_2
    text_2
    text_2

    So as you can see at the last part, I have three (or much more) instances (occurences) of the same “text_2.”
    When I run regex, will delete all the instances text_2.

    So, I want to delete just the last instance of text_2 in the regex. I will right again, but it should be modify a little bit for the second part.

    (?s)((^.*)(text_1)|(text_2)(.*$))



  • Hello Vasile,

    As you know, regexes force and help us to keep a rigorous attitude, as well as programming do ! So I, slightly, change your example text, in order to exactly see what you need !

    So, let’s suppose the example text, of 20 lines, below :

    Line 01
    Line 02
    Line 03 Text_1
    Line 04
    Line_05
    Text_1
    Line 07
    Line 08
    Line 09 Text_1
    Line_10
    Line_11
    Text_2 Line 12
    Line_13
    Line_14
    Text_2
    Line_16
    Line_17
    Text_2 Line_18
    Line_19
    Line_20
    

    Do you like to delete, in one go, :

    • All lines till the first occurrence of Text_1 ( so, lines 01,02 and 03 ) AND all lines from the first occurrence of Text_2 ( so, from lines 12 to 20 ) = case A

    • All lines till the first occurrence of Text_1 ( so, lines 01,02 and 03 ) AND all lines from the last occurrence of Text_2 ( so, lines 18, 19 and 20 ) = case B

    • All lines till the last occurrence of Text_1 ( so, from lines 01 to 09 ) AND all lines from the first occurrence of Text_2 ( so, from lines 12 to 20 ) = case C

    • All lines till the last occurrence of Text_1 ( so, from lines 01 to 09 ) AND all lines from the last occurrence of Text_2 ( so, lines 18, 19 and 20 ) = case D

    Just, tell me which case ( A, B, C or D ), we’ll have to find out the regex for ?

    Keep in mind, that I, implicitly, suppose that :

    • No string Text_1 may occur, after the first occurrence of string Text_2 !!

    • The strings Text_1 and/or Text_2 may appeared alone, in a line

    See you later,

    Best regards

    guy038

    P.S. :

    Anyway, Vasile, I updated my reply, one hour, later !

    Here are, below, the solution to the FOUR cases, given the exact previous example text, above.

    We just have to make, successively, each quantifier Star, lazy or greedy ! So :

    • Case A : SEARCH = (?s).*?Text_1\R(.*?)Text_2.* , which keeps the lines 04 to 11, only

    • Case B : SEARCH = (?s).*?Text_1\R(.*)Text_2.* , which keeps the lines 04 to 17, only

    • Case C : SEARCH = (?s).*Text_1\R(.*?)Text_2.* , which keeps the lines 10 to 11, only

    • Case D : SEARCH = (?s).*Text_1\R(.*)Text_2.* , which keeps the lines 10 to 17, only

    NOTE :

    • For these four cases, the replacement regex is, simply, \1 OR $1


  • guy, works great. But if I want to replace the entire line from fisrt part (?s).*?Text_1\R(.*?), so not only from a word, but the entire line that contains that word



  • guy038 should get paid a consulting rate for his excellent quality and quantity of answers! His perseverance is remarkable!



  • Guy, is a very talented and smart. He is the one that helps notepad users to grow and develop, step by step.

    Maybe someday, somebody will need the answers of my questions, and Guy is the one that make possible !

    Evolution starts with questions…and answers !

    by the way, I am not a programmer, in fact, I don’t have almost any connection with this domain. But, I learn basic, which helps me a lot in other way ! Thank you Guy038 !



  • Hello Vasile and Scott,

    Yeah, Scott, you’re right about it ! So, I could drink some more beers, as the weather is quite hot, presently, in Grenoble !!

    No problem, Vasile. So, I’m starting with the original text below :

    Line 01
    Line 02
    Line 03 Text_1 Line 03
    Line 04
    Line_05
    Line 06 Text_1 Line 06
    Line 07
    Line 08
    Line 09 Text_1 Line 09
    Line 10
    Line 11
    Line 12 Text_2 Line 12
    Line 13
    Line 14
    Line 15 Text_2 Line 15
    Line 16
    Line 17
    Line 18 Text_2 Line 18
    Line 19
    Line 20
    

    As you can see, this time, the strings Text_1 and Text_2, in lines 03, 06, 09, 12, 15 and 18 are, all, embedded in the template Line ##......Line ##


    I keep the same principle, using lazy and greedy quantifiers star *. That leads to the four regexes, below :

    • Case A : SEARCH = (?s).*?Text_1(?-s).*\R((?:.*\R)*?).*Text_2(?s).* , which keeps the lines 04 to 11

    • Case B : SEARCH = (?s).*?Text_1(?-s).*\R((?:.*\R)*).*Text_2(?s).* , which keeps the lines 04 to 17

    • Case C : SEARCH = (?s).*Text_1(?-s).*\R((?:.*\R)*?).*Text_2(?s).* , which keeps the lines 10 to 11

    • Case D : SEARCH = (?s).*Text_1(?-s).*\R((?:.*\R)*).*Text_2(?s).* , which keeps the lines 10 to 17

    Remark :

    • Remember that an in-line modifier keeps set, till an opposite modifier is met in the regex or till the end of the regex is reached !

    • The replacement regex has not changed : \1 or $1

    Cheers

    guy038

    P.S… :

    If some parts of the regexes seems too difficult, just ask me for further information ! It’s, simply, a question of mind’s gymnastics, that anyone can learn about !

    Also, try, to visualize the position of the regex engine, while executing the regex, especially when Look-Around ( Look-Behind or Look-Ahead ) are used. Indeed, in that case, the location of the regex engine does NOT change while evaluating the look-around !

    For instance, with the subject text This is a simple text to visualize the cursor location of the regex engine

    Then, the regex (?-s)(?=.*regex).{4} matches the four letters of this sentence ( the word this ). Let’s us split the process :

    • Cursor location is just before the first letter T of the text

    • The regex engine tries to verify if, from the present cursor location, the look-ahead. In other words, if there is, further on, on the same line, the string regex ?

    • As this condition is true, the regex engine goes on, executing the following regex code .{4}

    • But the working position of the regex engine, is, STILL, before the first letter T of the text !

    • Therefore, the regex engine matches the first four characters of the subject string, that is to say, the word this


    Note that IF the word regex would NOT have been found, in the text, the regex engine would have delivered the message :
    Can't find the text "(?-s)(?=.*regex).{4}" !



  • thanks a lot Guy !



  • hello Guy. And If I want to matc (in the last formulas) the first instance of Text_1 and the last instance of Text_2?



  • Hi Vasile,

    I, first, thought that the regex (?s).*?\KText_1|.*\KText_2 would give you the exact matches that you said :

    And If I want to match (in the last formulas) the first instance of Text_1 and the last instance of Text_2?

    Unfortunately, when using the search functionality, only, this regex matches any string Text_1, then the last string text_2 ! And, I was not able to get the right regex, which could find, in the current file, the first instance of Text_1, then the last instance of Text_2 :-((

    However, the regex (?s).*?\KText_1.*Text_2 allows us to select, in one go, all the gap, between these two specific boundaries, included !

    Best Regards,

    guy038


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