In the documentation I've not found the description of how to use capture groups in Elixir. How can I do that? Say, I want to extract a substring from a string and replace it with something else:
~r"\[tag1\](.+?)\[\/tag1\]"
How can I access the string in between ] [/?
Use Regex.run/3 for 1 match, Regex.scan/3 for all matches, or check out other functions in the Regex module.
iex(1)> regex = ~r"\[tag1\](.+?)\[\/tag1\]"
~r/\[tag1\](.+?)\[\/tag1\]/
iex(2)> [_, inner] = Regex.run(regex, "[tag1]bar[/tag1]")
["[tag1]bar[/tag1]", "bar"]
iex(3)> inner
"bar"
iex(4) Regex.scan(regex, "[tag1]bar[/tag1] [tag1]baz[/tag1]")
[["[tag1]bar[/tag1]", "bar"], ["[tag1]baz[/tag1]", "baz"]]
The docs do a good job at hiding it, but it's there: https://hexdocs.pm/elixir/1.0.5/Regex.html#replace/4
The replacement can be either a string or a function. The string is used as a replacement for every match and it allows specific captures to be accessed via \N or \g{N}, where N is the capture. In case \0 is used, the whole match is inserted.
Note: the \ in \N needs to be escaped so it will be \\N
Use Regex.replace/4 (or String.replace/4 when piping because the string is the first argument) to do this with one command.
You do not actually need to capture what is in between] [\ in the first place. You only need to match and replace it. This solution uses a "lookaround" which you can find more information on here: http://www.regular-expressions.info/lookaround.html
iex(1)> String.replace("[tag1]foo[/tag1]", ~r"\w+(?=\[)", "bar")
"[tag1]bar[/tag1]"
Related
I'm trying to allow users to filter strings of text using a glob pattern whose only control character is *. Under the hood, I figured the easiest thing to filter the list strings would be to use Js.Re.test[https://rescript-lang.org/docs/manual/latest/api/js/re#test_], and it is (easy).
Ignoring the * on the user filter string for now, what I'm having difficulty with is escaping all the RegEx control characters. Specifically, I don't know how to replace the capture groups within the input text to create a new string.
So far, I've got this, but it's not quite right:
let input = "test^ing?123[foo";
let escapeRegExCtrl = searchStr => {
let re = [%re("/([\\^\\[\\]\\.\\|\\\\\\?\\{\\}\\+][^\\^\\[\\]\\.\\|\\\\\\?\\{\\}\\+]*)/g")];
let break = ref(false);
while (!break.contents) {
switch (Js.Re.exec_ (re, searchStr)) {
| Some(result) => {
let match = Js.Re.captures(result)[0];
Js.log2("Matching: ", match)
}
| None => {
break := true;
}
}
}
};
search -> escapeRegExCtrl
If I disregard the "test" portion of the string being skipped, the above output will produce:
Matching: ^ing
Matching: ?123
Matching: [foo
With the above example, at the end of the day, what I'm trying to produce is this (with leading and following .*:
.*test\^ing\?123\[foo.*
But I'm unsure how to achieve creating a contiguous string from the matched capture groups.
(echo "test^ing?123[foo" | sed -r 's_([\^\?\[])_\\\1_g' would get the work done on the command line)
EDIT
Based on Chris Maurer's answer, there is a method in the JS library that does what I was looking for. A little digging exposed the ReasonML proxy for that method:
https://rescript-lang.org/docs/manual/latest/api/js/string#replacebyre
Let me see if I have this right; you want to implement a character matcher where everything is literal except *. Presumably the * is supposed to work like that in Windows dir commands, matching zero or more characters.
Furthermore, you want to implement it by passing a user-entered character string directly to a Regexp match function after suitably sanitizing it to only deal with the *.
If I have this right, then it sounds like you need to do two things to get the string ready for js.re.test:
Quote all the special regex characters, and
Turn all instances of * into .* or maybe .*?
Let's keep this simple and process the string in two steps, each one using Js.re.replace. So the list of special characters in regex are [^$.|?*+(). Suitably quoting these for replace:
str.replace(/[\[\\\^\$\.\|\?\+\(\)]/g, '\$&')
This is just all those special characters quoted. The $& in the replacement specifications says to insert whatever matched.
Then pass that result to a second replace for the * to .*? transformation.
str.replace(/*+/g, '.*?')
How can I extract a substring from within a string in Ruby?
Example:
String1 = "<name> <substring>"
I want to extract substring from String1 (i.e. everything within the last occurrence of < and >).
"<name> <substring>"[/.*<([^>]*)/,1]
=> "substring"
No need to use scan, if we need only one result.
No need to use Python's match, when we have Ruby's String[regexp,#].
See: http://ruby-doc.org/core/String.html#method-i-5B-5D
Note: str[regexp, capture] → new_str or nil
String1.scan(/<([^>]*)>/).last.first
scan creates an array which, for each <item> in String1 contains the text between the < and the > in a one-element array (because when used with a regex containing capturing groups, scan creates an array containing the captures for each match). last gives you the last of those arrays and first then gives you the string in it.
You can use a regular expression for that pretty easily…
Allowing spaces around the word (but not keeping them):
str.match(/< ?([^>]+) ?>\Z/)[1]
Or without the spaces allowed:
str.match(/<([^>]+)>\Z/)[1]
Here's a slightly more flexible approach using the match method. With this, you can extract more than one string:
s = "<ants> <pants>"
matchdata = s.match(/<([^>]*)> <([^>]*)>/)
# Use 'captures' to get an array of the captures
matchdata.captures # ["ants","pants"]
# Or use raw indices
matchdata[0] # whole regex match: "<ants> <pants>"
matchdata[1] # first capture: "ants"
matchdata[2] # second capture: "pants"
A simpler scan would be:
String1.scan(/<(\S+)>/).last
Beginner RegExp question. I have lines of JSON in a textfile, each with slightly different Fields, but there are 3 fields I want to extract for each line if it has it, ignoring everything else. How would I use a regex (in editpad or anywhere else) to do this?
Example:
"url":"http://www.netcharles.com/orwell/essays.htm",
"domain":"netcharles.com",
"title":"Orwell Essays & Journalism Section - Charles' George Orwell Links",
"tags":["orwell","writing","literature","journalism","essays","politics","essay","reference","language","toread"],
"index":2931,
"time_created":1345419323,
"num_saves":24
I want to extract URL,TITLE,TAGS,
/"(url|title|tags)":"((\\"|[^"])*)"/i
I think this is what you're asking for. I'll provide an explanation momentarily. This regular expression (delimited by / - you probably won't have to put those in editpad) matches:
"
A literal ".
(url|title|tags)
Any of the three literal strings "url", "title" or "tags" - in Regular Expressions, by default Parentheses are used to create groups, and the pipe character is used to alternate - like a logical 'or'. To match these literal characters, you'd have to escape them.
":"
Another literal string.
(
The beginning of another group. (Group 2)
(
Another group (3)
\\"
The literal string \" - you have to escape the backslash because otherwise it will be interpreted as escaping the next character, and you never know what that'll do.
|
or...
[^"]
Any single character except a double quote The brackets denote a Character Class/Set, or a list of characters to match. Any given class matches exactly one character in the string. Using a carat (^) at the beginning of a class negates it, causing the matcher to match anything that's not contained in the class.
)
End of group 3...
*
The asterisk causes the previous regular expression (in this case, group 3), to be repeated zero or more times, In this case causing the matcher to match anything that could be inside the double quotes of a JSON string.
)"
The end of group 2, and a literal ".
I've done a few non-obvious things here, that may come in handy:
Group 2 - when dereferenced using Backreferences - will be the actual string assigned to the field. This is useful when getting the actual value.
The i at the end of the expression makes it case insensitive.
Group 1 contains the name of the captured field.
EDIT: So I see that the tags are an array. I'll update the regular expression here in a second when I've had a chance to think about it.
Your new Regex is:
/"(url|title|tags)":("(\\"|[^"])*"|\[("(\\"|[^"])*"(,"(\\"|[^"])*")*)?\])/i
All I've done here is alternate the string regular expression I had been using ("((\\"|[^"])*)"), with a regular expression for finding arrays (\[("(\\"|[^"])*"(,"(\\"|[^"])*")*)?\]). No so easy to Read, is it? Well, substituting our String Regex out for the letter S, we can rewrite it as:
\[(S(,S)*)?\]
Which matches a literal opening bracket (hence the backslashes), optionally followed by a comma separated list of strings, and a closing bracket. The only new concept I've introduced here is the question mark (?), which is itself a type of repetition. Commonly referred to as 'making the previous expression optional', it can also be thought of as exactly 0 or 1 matches.
With our same S Notation, here's the whole dirty Regular Expression:
/"(url|title|tags)":(S|\[(S(,S)*)?\])/i
If it helps to see it in action, here's a view of it in action.
This question is a bit older, but I have had browsed a bit on my PC and found that expression. I passed him as GIST, could be useful to others.
EDIT:
# Expression was tested with PHP and Ruby
# This regular expression finds a key-value pair in JSON formatted strings
# Match 1: Key
# Match 2: Value
# https://regex101.com/r/zR2vU9/4
# http://rubular.com/r/KpF3suIL10
(?:\"|\')(?<key>[^"]*)(?:\"|\')(?=:)(?:\:\s*)(?:\"|\')?(?<value>true|false|[0-9a-zA-Z\+\-\,\.\$]*)
# test document
[
{
"_id": "56af331efbeca6240c61b2ca",
"index": 120000,
"guid": "bedb2018-c017-429E-b520-696ea3666692",
"isActive": false,
"balance": "$2,202,350",
"object": {
"name": "am",
"lastname": "lang"
}
}
]
the json string you'd like to extract field value from
{"fid":"321","otherAttribute":"value"}
the following regex expression extract exactly the "fid" field value "321"
(?<=\"fid\":\")[^\"]*
Please try below expression:
/"(url|title|tags)":("([^""]+)"|\[[^[]+])/gm
Explanation:
1st Capturing Group (url|title|tags): This is alternatively capturing the characters 'url','title' and 'tags' literally (case sensitive).
2nd Capturing Group ("([^""]+)"|[[^[]+]):
1st Alternative "([^""]+)" is matches all words within " and " including " and "
2nd Alternative [[^[]+] is matches all words within [ and ] including [ and ]
I have tested here
I adapted regex to work with JSON in my own library. I've detailed algorithm behavior below.
First, stringify the JSON object. Then, you need to store the starts and lengths of the matched substrings. For example:
"matched".search("ch") // yields 3
For a JSON string, this works exactly the same (unless you are searching explicitly for commas and curly brackets in which case I'd recommend some prior transform of your JSON object before performing regex (i.e. think :, {, }).
Next, you need to reconstruct the JSON object. The algorithm I authored does this by detecting JSON syntax by recursively going backwards from the match index. For instance, the pseudo code might look as follows:
find the next key preceding the match index, call this theKey
then find the number of all occurrences of this key preceding theKey, call this theNumber
using the number of occurrences of all keys with same name as theKey up to position of theKey, traverse the object until keys named theKey has been discovered theNumber times
return this object called parentChain
With this information, it is possible to use regex to filter a JSON object to return the key, the value, and the parent object chain.
You can see the library and code I authored at http://json.spiritway.co/
if your json is
{"key1":"abc","key2":"xyz"}
then below regex will extract key1 or key2 based on a key that you pass in regex
"key2(.*?)(?=,|}|$)
you can verify it here - regex101.com
Why does it have to be a Regular Expression object?
Here we can just use a Hash object first and then go search it.
mh = {"url":"http://www.netcharles.com/orwell/essays.htm","domain":"netcharles.com","title":"Orwell Essays & Journalism Section - Charles' George Orwell Links","tags":["orwell","writing","literature","journalism","essays","politics","essay","reference","language","toread"],"index":2931,"time_created":1345419323,"num_saves":24}
The output of which would be
=> {:url=>"http://www.netcharles.com/orwell/essays.htm", :domain=>"netcharles.com", :title=>"Orwell Essays & Journalism Section - Charles' George Orwell Links", :tags=>["orwell", "writing", "literature", "journalism", "essays", "politics", "essay", "reference", "language", "toread"], :index=>2931, :time_created=>1345419323, :num_saves=>24}
Not that I want to avoid using Regexp but don't you think it would be easier to take it a step at a time until your getting the data you want to further search through? Just MHO.
mh.values_at(:url, :title, :tags)
The output:
["http://www.netcharles.com/orwell/essays.htm", "Orwell Essays & Journalism Section - Charles' George Orwell Links", ["orwell", "writing", "literature", "journalism", "essays", "politics", "essay", "reference", "language", "toread"]]
Taking the pattern that FrankieTheKneeman gave you:
pattern = /"(url|title|tags)":"((\\"|[^"])*)"/i
we can search the mh hash by converting it to a json object.
/#{pattern}/.match(mh.to_json)
The output:
=> #<MatchData "\"url\":\"http://www.netcharles.com/orwell/essays.htm\"" 1:"url" 2:"http://www.netcharles.com/orwell/essays.htm" 3:"m">
Of course this is all done in Ruby which is not a tag that you have but relates I hope.
But oops! Looks like we can't do all three at once with that pattern so I will do them one at a time just for sake.
pattern = /"(title)":"((\\"|[^"])*)"/i
/#{pattern}/.match(mh.to_json)
#<MatchData "\"title\":\"Orwell Essays & Journalism Section - Charles' George Orwell Links\"" 1:"title" 2:"Orwell Essays & Journalism Section - Charles' George Orwell Links" 3:"s">
pattern = /"(tags)":"((\\"|[^"])*)"/i
/#{pattern}/.match(mh.to_json)
=> nil
Sorry about that last one. It will have to be handled differently.
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!";
}
}
Sorry in advance that this might be a little challenging to read...
I'm trying to parse a line (actually a subject line from an IMAP server) that looks like this:
=?utf-8?Q?Here is som?= =?utf-8?Q?e text.?=
It's a little hard to see, but there are two =?/?= pairs in the above line. (There will always be one pair; there can theoretically be many.) In each of those =?/?= pairs, I want the third argument (as defined by a ? delimiter) extracted. (In the first pair, it's "Here is som", and in the second it's "e text.")
Here's the regex I'm using:
=\?(.+)\?.\?(.*?)\?=
I want it to return two matches, one for each =?/?= pair. Instead, it's returning the entire line as a single match. I would have thought that the ? in the (.*?), to make the * operator lazy, would have kept this from happening, but obviously it doesn't.
Any suggestions?
EDIT: Per suggestions below to replace ".?" with "[^(\?=)]?" I'm now trying to do:
=\?(.+)\?.\?([^(\?=)]*?)\?=
...but it's not working, either. (I'm unsure whether [^(\?=)]*? is the proper way to test for exclusion of a two-character sequence like "?=". Is it correct?)
Try this:
\=\?([^?]+)\?.\?(.*?)\?\=
I changed the .+ to [^?]+, which means "everything except ?"
A good practice in my experience is not to use .*? but instead do use the * without the ?, but refine the character class. In this case [^?]* to match a sequence of non-question mark characters.
You can also match more complex endmarkers this way, for instance, in this case your end-limiter is ?=, so you want to match nonquestionmarks, and questionmarks followed by non-equals:
([^?]*\?[^=])*[^?]*
At this point it becomes harder to choose though. I like that this solution is stricter, but readability decreases in this case.
One solution:
=\?(.*?)\?=\s*=\?(.*?)\?=
Explanation:
=\? # Literal characters '=?'
(.*?) # Match each character until find next one in the regular expression. A '?' in this case.
\?= # Literal characters '?='
\s* # Match spaces.
=\? # Literal characters '=?'
(.*?) # Match each character until find next one in the regular expression. A '?' in this case.
\?= # Literal characters '?='
Test in a 'perl' program:
use warnings;
use strict;
while ( <DATA> ) {
printf qq[Group 1 -> %s\nGroup 2 -> %s\n], $1, $2 if m/=\?(.*?)\?=\s*=\?(.*?)\?=/;
}
__DATA__
=?utf-8?Q?Here is som?= =?utf-8?Q?e text.?=
Running:
perl script.pl
Results:
Group 1 -> utf-8?Q?Here is som
Group 2 -> utf-8?Q?e text.
EDIT to comment:
I would use the global modifier /.../g. Regular expression would be:
/=\?(?:[^?]*\?){2}([^?]*)/g
Explanation:
=\? # Literal characters '=?'
(?:[^?]*\?){2} # Any number of characters except '?' with a '?' after them. This process twice to omit the string 'utf-8?Q?'
([^?]*) # Save in a group next characters until found a '?'
/g # Repeat this process multiple times until end of string.
Tested in a Perl script:
use warnings;
use strict;
while ( <DATA> ) {
printf qq[Group -> %s\n], $1 while m/=\?(?:[^?]*\?){2}([^?]*)/g;
}
__DATA__
=?utf-8?Q?Here is som?= =?utf-8?Q?e text.?= =?utf-8?Q?more text?=
Running and results:
Group -> Here is som
Group -> e text.
Group -> more text
Thanks for everyone's answers! The simplest expression that solved my issue was this:
=\?(.*?)\?.\?(.*?)\?=
The only difference between this and my originally-posted expression was the addition of a ? (non-greedy) operator on the first ".*". Critical, and I'd forgotten it.