Regex: Select only the first instance of search results / first match
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@Alan-Kilborn said in Regex: Select only the first instance of search results / first match:
I was experimenting with your regex a bit and I noticed that not only did it match the text inside the final <tr></tr> pair, but it also matched the </tr> tag as well?
As I said it was from @PeterJones solution for the first instance. Thus in his post:
FIND = (?s)\A.?<tr>\s\K.?(\s</tr>)
REPLACE = new contents$1
MODE = regular expression
REPLACE ALL
then I getSo the replacement text would have been
new contents$1
, again same as the first instance solution. Sorry forgot to mention that.Terry
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so, conclusion. I select all regex from the las converstion:
Select and replace the first instance:
SEARCH:
(?s)\A.*?<tr>\s*\K.*?(\s*</tr>)(?=$)
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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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.*?\K
RE
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. -
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 anHTML
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>
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Tick the
Wrap around
option -
Click on the
Replace All
button, exclusively !
Now, to search for the last element
<tr> ••••• </tr>
, of anHTML
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 !
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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
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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
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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>
blockBest 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 ;-))
- The expression
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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>
blockSEARCH
(?s-i)\A.*<tr>\K.*?(?=</tr>)
to search ( and replace ) the last<tr> ••••• </tr>
blockAs usual, tick the
Regular expression
andWrap around
options and click on theReplace 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.*\K
REBest regards,
guy038
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@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
stoleborrowed 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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@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.*\KREYes, indeed.
That’s what I get for dabbling in the area of another master! :-) -
@guy038 thanks a lot !