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I'm going nuts trying to get a regex to detect spam of keywords in the user inputs. Usually there is some normal text at the start and the keyword spam at the end, separated by commas or other chars.
What I need is a regex to count the number of keywords to flag the text for a human to check it.
The text is usually like this:
[random text, with commas, dots and all]
keyword1, keyword2, keyword3, keyword4, keyword5,
Keyword6, keyword7, keyword8...
I've tried several regex to count the matches:
-This only gets one out of two keywords
[,-](\w|\s)+[,-]
-This also matches the random text
(?:([^,-]*)(?:[^,-]|$))
Can anyone tell me a regex to do this? Or should I take a different approach?
Thanks!
Pr your answer to my question, here is a regexp to match a string that occurs between two commas.
(?<=,)[^,]+(?=,)
This regexp does not match, and hence do not consume, the delimiting commas.
This regexp would match " and hence do not consume" in the previous sentence.
The fact that your regexp matched and consumed the commas was the reason why your attempted regexp only matched every other candidate.
Also if the whole input is a single string you will want to prevent linebreaks. In that case you will want to use;
(?<=,)[^,\n]+(?=,)
http://www.phpliveregex.com/p/1DJ
As others have said this is potentially a very tricky thing to do... It suffers from all of the same failures as general "word filtering" (e.g. people will "mask" the input). It is made even more difficult without plenty of example posts to test against...
Solution
Anyway, assuming that keywords will be on separate lines to the rest of the input and separated by commas you can match the lines with keywords in like:
Regex
#(?:^)((?:(?:[\w\.]+)(?:, ?|$))+)#m
Input
Taken from your question above:
[random text, with commas, dots and all]
keyword1, keyword2, keyword3, keyword4, keyword5,
Keyword6, keyword7, keyword8
Output
// preg_match_all('#(?:^)((?:(?:[\w]+)(?:, ?|$))+)#m', $string, $matches);
// var_dump($matches);
array(2) {
[0]=>
array(2) {
[0]=>
string(49) "keyword1, keyword2, keyword3, keyword4, keyword5,"
[1]=>
string(31) "Keyword6, keyword7, keyword8..."
}
[1]=>
array(2) {
[0]=>
string(49) "keyword1, keyword2, keyword3, keyword4, keyword5,"
[1]=>
string(31) "Keyword6, keyword7, keyword8"
}
}
Explanation
#(?:^)((?:(?:[\w]+)(?:, ?|$))+)#m
# => Starting delimiter
(?:^) => Matches start of line in a non-capturing group (you could just use ^ I was using |\n originally and didn't update)
( => Start a capturing group
(?: => Start a non-capturing group
(?:[\w]+) => A non-capturing group to match one or more word characters a-zA-Z0-9_ (Using a character class so that you can add to it if you need to....)
(?:, ?|$) => A non-capturing group to match either a comma (with an optional space) or the end of the string/line
)+ => End the non-capturing group (4) and repeat 5/6 to find multiple matches in the line
) => Close the capture group 3
# => Ending delimiter
m => Multi-line modifier
Follow up from number 2:
#^((?:(?:[\w]+)(?:, ?|$))+)#m
Counting keywords
Having now returned an array of lines only containing key words you can count the number of commas and thus get the number of keywords
$key_words = implode(', ', $matches[1]); // Join lines returned by preg_match_all
echo substr_count($key_words, ','); // 8
N.B. In most circumstances this will return NUMBER_OF_KEY_WORDS - 1 (i.e. in your case 7); it returns 8 because you have a comma at the end of your first line of key words.
Links
http://php.net/manual/en/reference.pcre.pattern.modifiers.php
http://www.regular-expressions.info/
http://php.net/substr_count
Why not just use explode and trim?
$keywords = array_map ('trim', explode (',', $keywordstring));
Then do a count() on $keywords.
If you think keywords with spaces in are spam, then you can iterate of the $keywords array and look for any that contain whitespace. There might be legitimate reasons for having spaces in a keyword though. If you're talking about superheroes on your system, for example, someone might enter The Tick or Iron Man as a keyword
I don't think counting keywords and looking for spaces in keywords are really very good strategies for detecting spam though. You might want to look into other bot protection strategies instead, or even use manual moderation.
How to match on the String of text between the commas?
This SO Post was marked as a duplicate to my posted question however since it is NOT a duplicate and there were no answers in THIS SO Post that answered my question on how to also match on the strings between the commas see below on how to take this a step further.
How to Match on single digit values in a CSV String
For example if the task is to search the string within the commas for a single 7, 8 or a single 9 but not match on combinations such as 17 or 77 or 78 but only the single 7s, 8s, or 9s see below...
The answer is to Use look arounds and place your search pattern within the look arounds:
(?<=^|,)[789](?=,|$)
See live demo.
The above Pattern is more concise however I've pasted below the Two Patterns provided as solutions to THIS this question of matching on Strings within the commas and they are:
(?<=^|,)[789](?=,|$) Provided by #Bohemian and chosen as the Correct Answer
(?:(?<=^)|(?<=,))[789](?:(?=,)|(?=$)) Provided in comments by #Ouroborus
Demo: https://regex101.com/r/fd5GnD/1
Your first regexp doesn't need a preceding comma
[\w\s]+[,-]
A regex that will match strings between two commas or start or end of string is
(?<=,|^)[^,]*(?=,|$)
Or, a bit more efficient:
(?<![^,])[^,]*(?![^,])
See the regex demo #1 and demo #2.
Details:
(?<=,|^) / (?<![^,]) - start of string or a position immediately preceded with a comma
[^,]* - zero or more chars other than a comma
(?=,|$) / (?![^,]) - end of string or a position immediately followed with a comma
If people still search for this in 2021
([^,\n])+
Match anything except new line and comma
regexr.com/60eme
I think the difficulty is that the random text can also contain commas.
If the keywords are all on one line and it is the last line of the text as a whole, trim the whole text removing new line characters from the end. Then take the text from the last new line character to the end. This should be your string containing the keywords. Once you have this part singled out, you can explode the string on comma and count the parts.
<?php
$string = " some gibberish, some more gibberish, and random text
keyword1, keyword2, keyword3
";
$lastEOL = strrpos(trim($string), PHP_EOL);
$keywordLine = substr($string, $lastEOL);
$keywords = explode(',', $keywordLine);
echo "Number of keywords: " . count($keywords);
I know it is not a regex, but I hope it helps nevertheless.
The only way to find a solution, is to find something that separates the random text and the keywords that is not present in the keywords. If a new line is present in the keywords, you can not use it. But are 2 consecutive new lines? Or any other characters.
$string = " some gibberish, some more gibberish, and random text
keyword1, keyword2, keyword3,
keyword4, keyword5, keyword6,
keyword7, keyword8, keyword9
";
$lastEOL = strrpos(trim($string), PHP_EOL . PHP_EOL); // 2 end of lines after random text
$keywordLine = substr($string, $lastEOL);
$keywords = explode(',', $keywordLine);
echo "Number of keywords: " . count($keywords);
(edit: added example for more new lines - long shot)
I am trying to split texts into "steps"
Lets say my text is
my $steps = "1.Do this. 2.Then do that. 3.And then maybe that. 4.Complete!"
I'd like the output to be:
"1.Do this."
"2.Then do that."
"3.And then maybe that."
"4.Complete!"
I'm not really that good with regex so help would be great!
I've tried many combination like:
split /(\s\d.)/
But it splits the numbering away from text
I would indeed use split. But you need to exclude the digit from the match by using a lookahead.
my #steps = split /\s+(?=\d+\.)/, $steps;
All step-descriptions start with a number followed by a period and then have non-numbers, until the next number. So capture all such patterns
my #s = $steps =~ / [0-9]+\. [^0-9]+ /xg;
say for #s;
This works only if there are surely no numbers in the steps' description, like any approach relying on matching a number (even if followed by a period, for decimal numbers)†
If there may be numbers in there, we'd need to know more about the structure of the text.
Another delimiting pattern to consider is punctuation that ends a sentence (. and ! in these examples), if there are no such characters in steps' description and there are no multiple sentences
my #s = $steps =~ / [0-9]+\. .*? [.!] /xg;
Augment the list of patterns that end an item's description as needed, say with a ?, and/or ." sequence as punctuation often goes inside quotes.‡
If an item can have multiple sentences, or use end-of-sentence punctuation mid-sentence (as a part of a quotation perhaps) then tighten the condition for an item's end by combining footnotes -- end-of-sentence punctuation and followed by number+period
my #s = $steps =~ /[0-9]+\. .*? (?: \."|\!"|[.\!]) (?=\s+[0-9]+\. | \z)/xg;
If this isn't good enough either then we'd really need a more precise description of that text.
† An approach using a "numbers-period" pattern to delimit item's description, like
/ [0-9]+\. .*? (?=\s+[0-9]+\. | \z) /xg;
(or in a lookahead in split) fails with text like
1. Only $2.50 or 1. Version 2.4.1 ...
‡ To include text like 1. Do "this." and 2. Or "that!" we'd want
/ [0-9]+\. .*? (?: \." | !" | [.!?]) /xg;
Following sample code demonstrates power of regex to fill up %steps hash in one line of code.
Once the data obtained you can dice and slice it anyway your heart desires.
Inspect the sample for compliance with your problem.
use strict;
use warnings;
use feature 'say';
use Data::Dumper;
my($str,%steps,$re);
$str = '1.Do this. 2.Then do that. 3.And then maybe that. 4.Complete!';
$re = qr/(\d+)\.(\D+)\./;
%steps = $str =~ /$re/g;
say Dumper(\%steps);
say "$_. $steps{$_}" for sort keys %steps;
Output
$VAR1 = {
'1' => 'Do this',
'2' => 'Then do that',
'3' => 'And then maybe that'
};
1. Do this
2. Then do that
3. And then maybe that
I'm having difficulty writing a Perl program to extract the word following a certain word.
For example:
Today i'm not going anywhere except to office.
I want the word after anywhere, so the output should be except.
I have tried this
my $words = "Today i'm not going anywhere except to office.";
my $w_after = ( $words =~ /anywhere (\S+)/ );
but it seems this is wrong.
Very close:
my ($w_after) = ($words =~ /anywhere\s+(\S+)/);
^ ^ ^^^
+--------+ |
Note 1 Note 2
Note 1: =~ returns a list of captured items, so the assignment target needs to be a list.
Note 2: allow one or more blanks after anywhere
In Perl v5.22 and later, you can use \b{wb} to get better results for natural language. The pattern could be
/anywhere\b{wb}.+?\b{wb}(.+?\b{wb})/
"wb" stands for word break, and it will account for words that have apostrophes in them, like "I'll", that plain \b doesn't.
.+?\b{wb}
matches the shortest non-empty sequence of characters that don't have a word break in them. The first one matches the span of spaces in your sentence; and the second one matches "except". It is enclosed in parentheses, so upon completion $1 contains "except".
\b{wb} is documented most fully in perlrebackslash
First, you have to write parentheses around left side expression of = operator to force array context for regexp evaluation. See m// and // in perlop documentation.[1] You can write
parentheses also around =~ binding operator to improve readability but it is not necessary because =~ has pretty high priority.
Use POSIX Character Classes word
my ($w_after) = ($words =~ / \b anywhere \W+ (\w+) \b /x);
Note I'm using x so whitespaces in regexp are ignored. Also use \b word boundary to anchor regexp correctly.
[1]: I write my ($w_after) just for convenience because you can write my ($a, $b, $c, #rest) as equivalent of (my $a, my $b, my $c, my #rest) but you can also control scope of your variables like (my $a, our $UGLY_GLOBAL, local $_, #_).
This Regex to be matched:
my ($expect) = ($words=~m/anywhere\s+([^\s]+)\s+/);
^\s+ the word between two spaces
Thanks.
If you want to also take into consideration the punctuation marks, like in:
my $words = "Today i'm not going anywhere; except to office.";
Then try this:
my ($w_after) = ($words =~ /anywhere[[:punct:]|\s]+(\S+)/);
I'm trying to learn something about regular expressions.
Here is what I'm going to match:
/parent/child
/parent/child?
/parent/child?firstparam=abc123
/parent/child?secondparam=def456
/parent/child?firstparam=abc123&secondparam=def456
/parent/child?secondparam=def456&firstparam=abc123
/parent/child?thirdparam=ghi789&secondparam=def456&firstparam=abc123
/parent/child?secondparam=def456&firstparam=abc123&thirdparam=ghi789
/parent/child?thirdparam=ghi789
/parent/child/
/parent/child/?
/parent/child/?firstparam=abc123
/parent/child/?secondparam=def456
/parent/child/?firstparam=abc123&secondparam=def456
/parent/child/?secondparam=def456&firstparam=abc123
/parent/child/?thirdparam=ghi789&secondparam=def456&firstparam=abc123
/parent/child/?secondparam=def456&firstparam=abc123&thirdparam=ghi789
/parent/child/?thirdparam=ghi789
My expression should "grabs" abc123 and def456.
And now just an example about what I'm not going to match ("question mark" is missing):
/parent/child/firstparam=abc123&secondparam=def456
Well, I built the following expression:
^(?:/parent/child){1}(?:^(?:/\?|\?)+(?:firstparam=([^&]*)|secondparam=([^&]*)|[^&]*)?)?
But that doesn't work.
Could you help me to understand what I'm doing wrong?
Thanks in advance.
UPDATE 1
Ok, I made other tests.
I'm trying to fix the previous version with something like this:
/parent/child(?:(?:\?|/\?)+(?:firstparam=([^&]*)|secondparam=([^&]*)|[^&]*)?)?$
Let me explain my idea:
Must start with /parent/child:
/parent/child
Following group is optional
(?: ... )?
The previous optional group must starts with ? or /?
(?:\?|/\?)+
Optional parameters (I grab values if specified parameters are part of querystring)
(?:firstparam=([^&]*)|secondparam=([^&]*)|[^&]*)?
End of line
$
Any advice?
UPDATE 2
My solution must be based just on regular expressions.
Just for example, I previously wrote the following one:
/parent/child(?:[?&/]*(?:firstparam=([^&]*)|secondparam=([^&]*)|[^&]*))*$
And that works pretty nice.
But it matches the following input too:
/parent/child/firstparam=abc123&secondparam=def456
How could I modify the expression in order to not match the previous string?
You didn't specify a language so I'll just usre Perl. So basically instead of matching everything, I just matched exactly what I thought you needed. Correct me if I am wrong please.
while ($subject =~ m/(?<==)\w+?(?=&|\W|$)/g) {
# matched text = $&
}
(?<= # Assert that the regex below can be matched, with the match ending at this position (positive lookbehind)
= # Match the character “=” literally
)
\\w # Match a single character that is a “word character” (letters, digits, and underscores)
+? # Between one and unlimited times, as few times as possible, expanding as needed (lazy)
(?= # Assert that the regex below can be matched, starting at this position (positive lookahead)
# Match either the regular expression below (attempting the next alternative only if this one fails)
& # Match the character “&” literally
| # Or match regular expression number 2 below (attempting the next alternative only if this one fails)
\\W # Match a single character that is a “non-word character”
| # Or match regular expression number 3 below (the entire group fails if this one fails to match)
\$ # Assert position at the end of the string (or before the line break at the end of the string, if any)
)
Output:
This regex will work as long as you know what your parameter names are going to be and you're sure that they won't change.
\/parent\/child\/?\?(?:(?:firstparam|secondparam|thirdparam)\=([\w]+)&?)(?:(?:firstparam|secondparam|thirdparam)\=([\w]+)&?)?(?:(?:firstparam|secondparam|thirdparam)\=([\w]+)&?)?
Whilst regex is not the best solution for this (the above code examples will be far more efficient, as string functions are way faster than regexes) this will work if you need a regex solution with up to 3 parameters. Out of interest, why must the solution use only regex?
In any case, this regex will match the following strings:
/parent/child?firstparam=abc123
/parent/child?secondparam=def456
/parent/child?firstparam=abc123&secondparam=def456
/parent/child?secondparam=def456&firstparam=abc123
/parent/child?thirdparam=ghi789&secondparam=def456&firstparam=abc123
/parent/child?secondparam=def456&firstparam=abc123&thirdparam=ghi789
/parent/child?thirdparam=ghi789
/parent/child/?firstparam=abc123
/parent/child/?secondparam=def456
/parent/child/?firstparam=abc123&secondparam=def456
/parent/child/?secondparam=def456&firstparam=abc123
/parent/child/?thirdparam=ghi789&secondparam=def456&firstparam=abc123
/parent/child/?secondparam=def456&firstparam=abc123&thirdparam=ghi789
/parent/child/?thirdparam=ghi789
It will now only match those containing query string parameters, and put them into capture groups for you.
What language are you using to process your matches?
If you are using preg_match with PHP, you can get the whole match as well as capture groups in an array with
preg_match($regex, $string, $matches);
Then you can access the whole match with $matches[0] and the rest with $matches[1], $matches[2], etc.
If you want to add additional parameters you'll also need to add them in the regex too, and add additional parts to get your data. For example, if you had
/parent/child/?secondparam=def456&firstparam=abc123&fourthparam=jkl01112&thirdparam=ghi789
The regex will become
\/parent\/child\/?\?(?:(?:firstparam|secondparam|thirdparam|fourthparam)\=([\w]+)&?)(?:(?:firstparam|secondparam|thirdparam|fourthparam)\=([\w]+)&?)?(?:(?:firstparam|secondparam|thirdparam|fourthparam)\=([\w]+)&?)?(?:(?:firstparam|secondparam|thirdparam|fourthparam)\=([\w]+)&?)?
This will become a bit more tedious to maintain as you add more parameters, though.
You can optionally include ^ $ at the start and end if the multi-line flag is enabled. If you also need to match the whole lines without query strings, wrap this whole regex in a non-capture group (including ^ $) and add
|(?:^\/parent\/child\/?\??$)
to the end.
You're not escaping the /s in your regex for starters and using {1} for a single repetition of something is unnecessary; you only use those when you want more than one repetition or a range of repetitions.
And part of what you're trying to do is simply not a good use of a regex. I'll show you an easier way to deal with that: you want to use something like split and put the information into a hash that you can check the contents of later. Because you didn't specify a language, I'm just going to use Perl for my example, but every language I know with regexes also has easy access to hashes and something like split, so this should be easy enough to port:
# I picked an example to show how this works.
my $route = '/parent/child/?first=123&second=345&third=678';
my %params; # I'm going to put those URL parameters in this hash.
# Perl has a way to let me avoid escaping the /s, but I wanted an example that
# works in other languages too.
if ($route =~ m/\/parent\/child\/\?(.*)/) { # Use the regex for this part
print "Matched route.\n";
# But NOT for this part.
my $query = $1; # $1 is a Perl thing. It contains what (.*) matched above.
my #items = split '&', $query; # Each item is something like param=123
foreach my $item (#items) {
my ($param, $value) = split '=', $item;
$params{$param} = $value; # Put the parameters in a hash for easy access.
print "$param set to $value \n";
}
}
# Now you can check the parameter values and do whatever you need to with them.
# And you can add new parameters whenever you want, etc.
if ($params{'first'} eq '123') {
# Do whatever
}
My solution:
/(?:\w+/)*(?:(?:\w+)?\?(?:\w+=\w+(?:&\w+=\w+)*)?|\w+|)
Explain:
/(?:\w+/)* match /parent/child/ or /parent/
(?:\w+)?\?(?:\w+=\w+(?:&\w+=\w+)*)? match child?firstparam=abc123 or ?firstparam=abc123 or ?
\w+ match text like child
..|) match nothing(empty)
If you need only query string, pattern would reduce such as:
/(?:\w+/)*(?:\w+)?\?(\w+=\w+(?:&\w+=\w+)*)
If you want to get every parameter from query string, this is a Ruby sample:
re = /\/(?:\w+\/)*(?:\w+)?\?(\w+=\w+(?:&\w+=\w+)*)/
s = '/parent/child?secondparam=def456&firstparam=abc123&thirdparam=ghi789'
if m = s.match(re)
query_str = m[1] # now, you can 100% trust this string
query_str.scan(/(\w+)=(\w+)/) do |param,value| #grab parameter
printf("%s, %s\n", param, value)
end
end
output
secondparam, def456
firstparam, abc123
thirdparam, ghi789
This script will help you.
First, i check, is there any symbol like ?.
Then, i kill first part of line (left from ?).
Next, i split line by &, where each value splitted by =.
my $r = q"/parent/child
/parent/child?
/parent/child?firstparam=abc123
/parent/child?secondparam=def456
/parent/child?firstparam=abc123&secondparam=def456
/parent/child?secondparam=def456&firstparam=abc123
/parent/child?thirdparam=ghi789&secondparam=def456&firstparam=abc123
/parent/child?secondparam=def456&firstparam=abc123&thirdparam=ghi789
/parent/child?thirdparam=ghi789
/parent/child/
/parent/child/?
/parent/child/?firstparam=abc123
/parent/child/?secondparam=def456
/parent/child/?firstparam=abc123&secondparam=def456
/parent/child/?secondparam=def456&firstparam=abc123
/parent/child/?thirdparam=ghi789&secondparam=def456&firstparam=abc123
/parent/child/?secondparam=def456&firstparam=abc123&thirdparam=ghi789
/parent/child/?thirdparam=ghi789";
for my $string(split /\n/, $r){
if (index($string,'?')!=-1){
substr($string, 0, index($string,'?')+1,"");
#say "string = ".$string;
if (index($string,'=')!=-1){
my #params = map{$_ = [split /=/, $_];}split/\&/, $string;
$"="\n";
say "$_->[0] === $_->[1]" for (#params);
say "######next########";
}
else{
#print "there is no params!"
}
}
else{
#say "there is no params!";
}
}
As stated in the title, is there a way, using regular expressions, to match a text pattern for text that appears outside of quotes. Ideally, given the following examples, I would want to be able to match the comma that is outside of the quotes, but not the one in the quotes.
This is some text, followed by "text, in quotes!"
or
This is some text, followed by "text, in quotes" with more "text, in quotes!"
Additionally, it would be nice if the expression would respect nested quotes as in the following example. However, if this is technically not feasible with regular expressions then it wold simply be nice to know if that is the case.
The programmer looked up from his desk, "This can't be good," he exclaimed, "the system is saying 'File not found!'"
I have found some expressions for matching something that would be in the quotes, but nothing quite for something outside of the quotes.
Easiest is matching both commas and quoted strings, and then filtering out the quoted strings.
/"[^"]*"|,/g
If you really can't have the quotes matching, you could do something like this:
/,(?=[^"]*(?:"[^"]*"[^"]*)*\Z)/g
This could become slow, because for each comma, it has to look at the remaining characters and count the number of quotes. \Z matches the end of the string. Similar to $, but will never match line ends.
If you don't mind an extra capture group, it could be done like this instead:
/\G((?:[^"]*"[^"]*")*?[^"]*?)(,)/g
This will only scan the string once. It counts the quotes from the beginning of the string instead. \G will match the position where last match ended.
The last pattern could need an example.
Input String: 'This is, some text, followed by "text, in quotes!" and more ,-as'
Matches:
1. ['This is', ',']
2. [' some text', ',']
3. [' and followed by "text, in quotes!" and more ', ',']
It matches the string leading up to the comma, as well as the comma.
This can be done with modern regexes due to the massive number of hacks to regex engines that exist, but let me be the one to post the "Don't Do This With Regular Expressions" answer.
This is not a job for regular expressions. This is a job for a full-blown parser. As an example of something you can't do with (classical) regular expressions, consider this:
()(())(()())
No (classical) regex can determine if those parenthesis are matched properly, but doing so without a regex is trivial:
/* C code */
char string[] = "()(())(()())";
int parens = 0;
for(char *tmp = string; tmp; tmp++)
{
if(*tmp == '(') parens++;
if(*tmp == ')') parens--;
}
if(parens > 0)
{
printf("%s too many open parenthesis.\n", parens);
}
else if(parens < 0)
{
printf("%s too many closing parenthesis.\n", -parens);
}
else
{
printf("Parenthesis match!\n");
}
# Perl code
my $string = "()(())(()())";
my $parens = 0;
for(split(//, $string)) {
$parens++ if $_ eq "(";
$parens-- if $_ eq ")";
}
die "Too many open parenthesis.\n" if $parens > 0;
die "Too many closing parenthesis.\n" if $parens < 0;
print "Parenthesis match!";
See how simple it was to write some non-regex code to do the job for you?
EDIT: Okay, back from seeing Adventureland. :) Try this (written in Perl, commented to help you understand what I'm doing if you don't know Perl):
# split $string into a list, split on the double quote character
my #temp = split(/"/, $string);
# iterate through a list of the number of elements in our list
for(0 .. $#temp) {
# skip odd-numbered elements - only process $list[0], $list[2], etc.
# the reason is that, if we split on "s, every other element is a string
next if $_ & 1;
if($temp[$_] =~ /regex/) {
# do stuff
}
}
Another way to do it:
my $bool = 0;
my $str;
my $match;
# loop through the characters of a string
for(split(//, $string)) {
if($_ eq '"') {
$bool = !$bool;
if($bool) {
# regex time!
$match += $str =~ /regex/;
$str = "";
}
}
if(!$bool) {
# add the current character to our test string
$str .= $_;
}
}
# get trailing string match
$match += $str =~ /regex/;
(I give two because, in another language, one solution may be easier to implement than the other, not just because There's More Than One Way To Do It™.)
Of course, as your problems grow in complexity, there will arise certain benefits of constructing a full-blown parser, but that's a different horse. For now, this will suffice.
As mentioned before, regexp cannot match any nested pattern, since it is not a Context-free language.
So if you have any nested quotes, you are not going to solve this with a regex.
(Except with the "balancing group" feature of a .Net regex engine - as mentioned by Daniel L in the comments - , but I am not making any assumption of the regex flavor here)
Except if you add further specification, like a quote within a quote must be escaped.
In that case, the following:
text before string "string with \escape quote \" still
within quote" text outside quote "within quote \" still inside" outside "
inside" final outside text
would be matched successfully with:
(?ms)((?:\\(?=")|[^"])+)(?:"((?:[^"]|(?<=\\)")+)(?<!\\)")?
group1: text preceding a quoted text
group2: text within double quotes, even if \" are present in it.
Here is an expression that gets the match, but it isn't perfect, as the first match it gets is the whole string, removing the final ".
[^"].*(,).*[^"]
I have been using my Free RegEx tester to see what works.
Test Results
Group Match Collection # 1
Match # 1
Value: This is some text, followed by "text, in quotes!
Captures: 1
Match # 2
Value: ,
Captures: 1
You should better build yourself a simple parser (pseudo-code):
quoted := False
FOR char IN string DO
IF char = '"'
quoted := !quoted
ELSE
IF char = "," AND !quoted
// not quoted comma found
ENDIF
ENDIF
ENDFOR
This really depends on if you allow nested quotes or not.
In theory, with nested quotes you cannot do this (regular languages can't count)
In practice, you might manage if you can constrain the depth. It will get increasingly ugly as you add complexity. This is often how people get into grief with regular expressions (trying to match something that isn't actually regular in general).
Note that some "regex" libraries/languages have added non-regular features.
If this sort of thing gets complicated enough, you'll really have to write/generate a parser for it.
You need more in your description. Do you want any set of possible quoted strings and non-quoted strings like this ...
Lorem ipsum "dolor sit" amet, "consectetur adipiscing" elit.
... or simply the pattern you asked for? This is pretty close I think ...
(?<outside>.*?)(?<inside>(?=\"))
It does capture the "'s however.
Maybe you could do it in two steps?
First you replace the quoted text:
("[^"]*")
and then you extract what you want from the remaining string
,(?=(?:[^"]*"[^"]*")*[^"]*\z)
Regexes may not be able to count, but they can determine whether there's an odd or even number of something. After finding a comma, the lookahead asserts that, if there are any quotation marks ahead, there's an even number of them, meaning the comma is not inside a set of quotes.
This can be tweaked to handle escaped quotes if needed, though the original question didn't mention that. Also, if your regex flavor supports them, I would add atomic groups or possessive quantifiers to keep backtracking in check.