first I used a string that returned my relaystates, so “1.0.0.0.1.1.0.0” would get parsed/grouped with \d+,
then my eight switches used ‘format response’, e.g. {1} to get the state for each switch.
now I need to get the numbers out of this string: “RELAYS.1.0.0.0.1.1.0.0”
\d+ will still get the numbers but I only want to get them IF the string starts with “RELAYS"
can anyone please explain how I could do that?
thnx a million in advance!
Edited icebear (today 00:24)
With a .NET engine, you could use the regex (?<=^RELAYS[\d.]*)\d+. But most regex engines don't support indefinite repetition in a negative lookbehind assertion.
See it live on regexhero.net.
Explanation:
(?<= # Assert that the following can be matched before the current position:
^RELAYS # Start of string, followed by "RELAYS"
[\d.]* # and any number of digits/dots.
) # End of lookbehind assertion
\d+ # Match one or more digits.
With a PCRE engine, you could use (?:^RELAYS\.|\G\.)(\d+) and access group 1 for each match.
See it live on regex101.com.
Explanation:
(?: # Start a non-capturing group that matches...
^RELAYS\. # either the start of the string and "RELAYS."
| # or
\G\. # the position after the previous match, followed by "."
) # End of non-capturing group
(\d+) # Match a number and capture it in group 1
Related
I'm trying to match the url https://youtube.com/embed/id and its parameters i.e ?start=10&autoplay=1, but I need the autoplay parameter removed or set to 0.
These are some example urls and what I want the results to look like:
http://www.youtube.com/embed/JW5meKfy3fY?autoplay=1
I want to remove the autoplay parameter and its value:
http://www.youtube.com/embed/JW5meKfy3fY
2nd example
http://www.youtube.com/embed/JW5meKfy3fY?start=10&autoplay=1
results should be
http://www.youtube.com/embed/JW5meKfy3fY?start=10
I have tried (https?:\/\/www.youtube.com\/embed\/[a-zA-Z0-9\\-_]+)(\?[^\t\n\f\r \"']*)(\bautoplay=[01]\b&?) and replace with $1$2, but it matches with a trailing ? and & in example 1 and 2 respectively. Also, it doesn't match at all for a url like
http://www.youtube.com/embed/JW5meKfy3fY
I have the regex and examples on here
NB:
The string I am working on contains HTML with one or more youtube urls in it, so I don't think I can easily use go's net/url package to parse the url.
You're asking for a regex but I think you'd be better off using Go's "net/url" package. Something like this:
import "net/url"
//...
u, _ := url.Parse("http://www.youtube.com/embed/JW5meKfy3fY?start=10&autoplay=1")
q := u.Query()
q.Del("autoplay")
u.RawQuery = q.Encode()
clean_url_string = u.String()
In real life you'd want to handle errors from u.Parse of course.
Here's a solution that ensures a valid page URI. Simply match this and only return capture group 1 and 3.
Edit: The pattern is not elegant but it ensures no stale ampersands stay. The previous solution was more elegant and albeit wouldn't break anything, isn't worth the tradeoff imo.
Pattern
(https?:\/\/www\.youtube\.com\/embed\/[^?]+\?.*)(&autoplay=[01]|autoplay=[01]&?)(.*)
See the demo here.
As the OP has linked to a regex tester that employs the the PCRE (PHP) engine I offer a PCRE-compatible solution. The one token I've used in the regular expression below that is not widely supported in other regex engines is \K (though it is supported by Perl, Ruby, Python's PyPI regex module, R with Perl=TRUE and possibly other engines.
\K causes the regex engine to reset the beginning of the match to the current location in the string and to discard any previously-matched characters in the match it returns (if there is one).
With one caveat you can replace matches of the following regular expression with empty strings.
(?x) # assert 'extended'/'free spacing' mode
\bhttps?:\/\/www.youtube.com\/embed\/
# match literal
(?=.*autoplay=[01]) # positive lookahead asserts 'autoplay='
# followed by '1' or '2' appears later in
# the string
[a-zA-Z0-9\\_-]+ # match 1+ of the chars in the char class
[^\t\n\f\r \"']* # match 0+ chars other than those in the
# char class
(?<![?&]) # negative lookbehind asserts that previous
# char was neither '?' nor '&'
(?: # begin non-capture group
(?=\?) # use positive lookahead to assert next char
# is a '?'
(?: # begin a non-capture group
(?=.*autoplay=[01]&)
# positive lookahead asserts 'autoplay='
# followed by '1' or '2', then '&' appears
# later in the string
\? # match '?'
)? # end non-capture group and make it optional
\K # reset start of match to current location
# and discard all previously-matched chars
\?? # optionally match '?'
autoplay=[01]&? # match 'autoplay=' followed by '1' or '2',
# optionally followed by '&'
| # or
(?=&) # positive lookahead asserts next char is '&'
\K # reset start of match to current location
# and discard all previously-matched chars
&autoplay=[01]&? # match '&autoplay=' followed by '1' or '2',
# optionally followed by '&'
) # end non-capture group
The one limitation is that it fails to match all instances of .autoplay=.. if more than one such substring appears in the string.
I wrote this expression with the x flag, called extended or free spacing mode, to be able to make it self-documenting.
Start your engine!
I'm new to regex. Facing some issues while making one expression as optional and if it exists then it should not be repeated. In the below case I want %23 to be optional and if it occurs then it should not be repeated. But in below case it's working for optional but not for repeat case.
It's giving me true even if I put string as:
-113%23%2313113098A%2F--
Could someone suggest how to make it optional and not repetitive. This is my regex:
(%23)?([0-9]|[A-Z]|%2F|-).*$
You can use a negative lookahead to avoid matching repeating instances of %23:
^(?:[0-9]|[A-Z]|%2F|[-%])(?!(?:.*?%23){2}).*$
Breakup:
(?! # start negative lookahead
(?:.*?%23){2} # match 0 or more chars followed by %23, {2} matches 2 repeats
) # end lookahead
RegEx Demo
However if requirement is to avoid consecutive repeats then use:
^(?!.*?(?:%23){2})
I have string like "smth 2sg. smth", and sometimes "smth 2sg.| smth.".
What mask should I use for selecting "2sg." if string does not contains"|", and select nothing if string does contains "|"?
I have 2 methods. They both use something called a Negative Lookahead, which is used like so:
(?!data)
When this is inserted into a RegEx, it means if data exists, the RegEx will not match.
More info on the Negative Lookahead can be found here
Method 1 (shorter)
Just capture 2sg.
Try this RegEx:
(\dsg\.)(?!\|)
Use (\d+... if the number could be longer than 1 digit
Live Demo on RegExr
How it works:
( # To capture (2sg.)
\d # Digit (2)
sg # (sg)
\. # . (Dot)
)
(?!\|) # Do not match if contains |
Method 2 (longer but safer)
Match the whole string and capture 2sg.
Try this RegEx:
^\w+\s*(\dsg\.)(?!\|)\s*\w+\.?$
Use (\d+sg... if the number could be longer than 1 digit
Live Demo on RegExr
How it works:
^ # String starts with ...
\w+\s* # Letters then Optional Whitespace (smth )
( # To capture (2sg.)
\d # Digit (2)
sg # (sg)
\. # . (Dot)
)
(?!\|) # Do not match if contains |
\s* # Optional Whitespace
\w+ # Letters (smth)
\.? # Optional . (Dot)
$ # ... Strings ends with
Something like this might work for you:
(\d*sg\.)(?!\|)
It assumes that there is(or there is no)number followed by sg. and not followed by |.
^.*(\dsg\.)[^\|]*$
Explanation:
^ : starts from the beginning of the string
.* : accepts any number of initial characters (even nothing)
(\dsg\.) : looks for the group of digit + "sg."
[^\|]* : considers any number of following characters except for |
$ : stops at the end of the string
You can now select your string by getting the first group from your regex
Try:
(\d+sg.(?!\|))
depending on your programming environment, it can be little bit different but will get your result.
For more information see Negative Lookahead
I have strings like
wwww-wwww-wwww
wwww-www-ww-ww
Many w separated with -
But it's not regular wwww-wwww, it could be w-w-w-w as well
I try to find a regex that capture every word until the last 4 words.
So the result for example 1 would be the first 8w's (wwww-wwww)
For 2nd example the first 5w's (wwww-w)
Is it possible to do this in regex?
I have something like this right now:
^\w*(?=\w{4}$)
or maybe
[^-]*(?=\w{4}$)
I have 2 problems with my "solutions":
the last 4 words will not be captured for example 2. They are interrupted by the -
the words before the last 4 will not be captured. They are interrupted by the -.
Yes, it's possible with a slightly more sophisticated lookahead assertion:
/\w(?=(?:-*\w){4,}$)/x
Explanation:
/ # Start of regex
\w # Match a "word" character
(?= # only if the following can be matched afterwards:
(?: # (Start of capturing group)
-* # - zero or more separators
\w # - exactly one word character
){4,} # (End of capturing group), repeated 4 or more times.
$ # Then make sure we've reached the end of the string.
) # End of lookahead assertion/x
Test it live on regex101.com.
In a text editor, I want to replace a given word with the number of the line number on which this word is found. Is this is possible with Regex?
Recursion, Self-Referencing Group (Qtax trick), Reverse Qtax or Balancing Groups
Introduction
The idea of adding a list of integers to the bottom of the input is similar to a famous database hack (nothing to do with regex) where one joins to a table of integers. My original answer used the #Qtax trick. The current answers use either Recursion, the Qtax trick (straight or in a reversed variation), or Balancing Groups.
Yes, it is possible... With some caveats and regex trickery.
The solutions in this answer are meant as a vehicle to demonstrate some regex syntax more than practical answers to be implemented.
At the end of your file, we will paste a list of numbers preceded with a unique delimiter. For this experiment, the appended string is :1:2:3:4:5:6:7 This is a similar technique to a famous database hack that uses a table of integers.
For the first two solutions, we need an editor that uses a regex flavor that allows recursion (solution 1) or self-referencing capture groups (solutions 2 and 3). Two come to mind: Notepad++ and EditPad Pro. For the third solution, we need an editor that supports balancing groups. That probably limits us to EditPad Pro or Visual Studio 2013+.
Input file:
Let's say we are searching for pig and want to replace it with the line number.
We'll use this as input:
my cat
dog
my pig
my cow
my mouse
:1:2:3:4:5:6:7
First Solution: Recursion
Supported languages: Apart from the text editors mentioned above (Notepad++ and EditPad Pro), this solution should work in languages that use PCRE (PHP, R, Delphi), in Perl, and in Python using Matthew Barnett's regex module (untested).
The recursive structure lives in a lookahead, and is optional. Its job is to balance lines that don't contain pig, on the left, with numbers, on the right: think of it as balancing a nested construct like {{{ }}}... Except that on the left we have the no-match lines, and on the right we have the numbers. The point is that when we exit the lookahead, we know how many lines were skipped.
Search:
(?sm)(?=.*?pig)(?=((?:^(?:(?!pig)[^\r\n])*(?:\r?\n))(?:(?1)|[^:]+)(:\d+))?).*?\Kpig(?=.*?(?(2)\2):(\d+))
Free-Spacing Version with Comments:
(?xsm) # free-spacing mode, multi-line
(?=.*?pig) # fail right away if pig isn't there
(?= # The Recursive Structure Lives In This Lookahead
( # Group 1
(?: # skip one line
^
(?:(?!pig)[^\r\n])* # zero or more chars not followed by pig
(?:\r?\n) # newline chars
)
(?:(?1)|[^:]+) # recurse Group 1 OR match all chars that are not a :
(:\d+) # match digits
)? # End Group
) # End lookahead.
.*?\Kpig # get to pig
(?=.*?(?(2)\2):(\d+)) # Lookahead: capture the next digits
Replace: \3
In the demo, see the substitutions at the bottom. You can play with the letters on the first two lines (delete a space to make pig) to move the first occurrence of pig to a different line, and see how that affects the results.
Second Solution: Group that Refers to Itself ("Qtax Trick")
Supported languages: Apart from the text editors mentioned above (Notepad++ and EditPad Pro), this solution should work in languages that use PCRE (PHP, R, Delphi), in Perl, and in Python using Matthew Barnett's regex module (untested). The solution is easy to adapt to .NET by converting the \K to a lookahead and the possessive quantifier to an atomic group (see the .NET Version a few lines below.)
Search:
(?sm)(?=.*?pig)(?:(?:^(?:(?!pig)[^\r\n])*(?:\r?\n))(?=[^:]+((?(1)\1):\d+)))*+.*?\Kpig(?=[^:]+(?(1)\1):(\d+))
.NET version: Back to the Future
.NET does not have \K. It its place, we use a "back to the future" lookbehind (a lookbehind that contains a lookahead that skips ahead of the match). Also, we need to use an atomic group instead of a possessive quantifier.
(?sm)(?<=(?=.*?pig)(?=(?>(?:^(?:(?!pig)[^\r\n])*(?:\r?\n))(?=[^:]+((?(1)\1):\d+)))*).*)pig(?=[^:]+(?(1)\1):(\d+))
Free-Spacing Version with Comments (Perl / PCRE Version):
(?xsm) # free-spacing mode, multi-line
(?=.*?pig) # lookahead: if pig is not there, fail right away to save the effort
(?: # start counter-line-skipper (lines that don't include pig)
(?: # skip one line
^ #
(?:(?!pig)[^\r\n])* # zero or more chars not followed by pig
(?:\r?\n) # newline chars
)
# for each line skipped, let Group 1 match an ever increasing portion of the numbers string at the bottom
(?= # lookahead
[^:]+ # skip all chars that are not colons
( # start Group 1
(?(1)\1) # match Group 1 if set
:\d+ # match a colon and some digits
) # end Group 1
) # end lookahead
)*+ # end counter-line-skipper: zero or more times
.*? # match
\K # drop everything we've matched so far
pig # match pig (this is the match!)
(?=[^:]+(?(1)\1):(\d+)) # capture the next number to Group 2
Replace:
\2
Output:
my cat
dog
my 3
my cow
my mouse
:1:2:3:4:5:6:7
In the demo, see the substitutions at the bottom. You can play with the letters on the first two lines (delete a space to make pig) to move the first occurrence of pig to a different line, and see how that affects the results.
Choice of Delimiter for Digits
In our example, the delimiter : for the string of digits is rather common, and could happen elsewhere. We can invent a UNIQUE_DELIMITER and tweak the expression slightly. But the following optimization is even more efficient and lets us keep the :
Optimization on Second Solution: Reverse String of Digits
Instead of pasting our digits in order, it may be to our benefit to use them in the reverse order: :7:6:5:4:3:2:1
In our lookaheads, this allows us to get down to the bottom of the input with a simple .*, and to start backtracking from there. Since we know we're at the end of the string, we don't have to worry about the :digits being part of another section of the string. Here's how to do it.
Input:
my cat pi g
dog p ig
my pig
my cow
my mouse
:7:6:5:4:3:2:1
Search:
(?xsm) # free-spacing mode, multi-line
(?=.*?pig) # lookahead: if pig is not there, fail right away to save the effort
(?: # start counter-line-skipper (lines that don't include pig)
(?: # skip one line that doesn't have pig
^ #
(?:(?!pig)[^\r\n])* # zero or more chars not followed by pig
(?:\r?\n) # newline chars
)
# Group 1 matches increasing portion of the numbers string at the bottom
(?= # lookahead
.* # get to the end of the input
( # start Group 1
:\d+ # match a colon and some digits
(?(1)\1) # match Group 1 if set
) # end Group 1
) # end lookahead
)*+ # end counter-line-skipper: zero or more times
.*? # match
\K # drop match so far
pig # match pig (this is the match!)
(?=.*(\d+)(?(1)\1)) # capture the next number to Group 2
Replace: \2
See the substitutions in the demo.
Third Solution: Balancing Groups
This solution is specific to .NET.
Search:
(?m)(?<=\A(?<c>^(?:(?!pig)[^\r\n])*(?:\r?\n))*.*?)pig(?=[^:]+(?(c)(?<-c>:\d+)*):(\d+))
Free-Spacing Version with Comments:
(?xm) # free-spacing, multi-line
(?<= # lookbehind
\A #
(?<c> # skip one line that doesn't have pig
# The length of Group c Captures will serve as a counter
^ # beginning of line
(?:(?!pig)[^\r\n])* # zero or more chars not followed by pig
(?:\r?\n) # newline chars
) # end skipper
* # repeat skipper
.*? # we're on the pig line: lazily match chars before pig
) # end lookbehind
pig # match pig: this is the match
(?= # lookahead
[^:]+ # get to the digits
(?(c) # if Group c has been set
(?<-c>:\d+) # decrement c while we match a group of digits
* # repeat: this will only repeat as long as the length of Group c captures > 0
) # end if Group c has been set
:(\d+) # Match the next digit group, capture the digits
) # end lokahead
Replace: $1
Reference
Qtax trick
On Which Line Number Was the Regex Match Found?
Because you didn't specify which text editor, in vim it would be:
:%s/searched_word/\=printf('%-4d', line('.'))/g (read more)
But as somebody mentioned it's not a question for SO but rather Super User ;)
I don't know of an editor that does that short of extending an editor that allows arbitrary extensions.
You could easily use perl to do the task, though.
perl -i.bak -e"s/word/$./eg" file
Or if you want to use wildcards,
perl -MFile::DosGlob=glob -i.bak -e"BEGIN { #ARGV = map glob($_), #ARGV } s/word/$./eg" *.txt