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Reference - What does this regex mean?
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Basically I have a bunch of strings in a database and I need to split them into 3 parts.
First part should be the very first word, nothing else, so I can use explode for that.
The second and third parts are tricky, as the string and word length is not consistent, for example:
Michelin Alpin 3 185/70 R14 GRNX --> [Michelin] [Alpin 3] [185/70 R14 GRNX]
Continental VancoWinter 2 225/75 R16C C M+S --> [Continental] [VancoWinter 2] [225/75 R16C C M+S]
Kleber VIAXER 175/70 R13 82T --> [Kleber] [VIAXER] [175/70 R13 82T]
I tried quite a few regex patterns to get these 3 parts back, but no luck so far.
I would really appreciate any ideas!
Unfortunately I cannot see a clear and concise logic to follow. The second part is Alpin 3 and VancoWinter 2, but not VIAXER 175. So you first need to define your desired outcome.
However, just based on these examples, this might or might not work:
^(\S*) (.*) (\d+\/\d+.*)
Try it online: https://regex101.com/r/4rtbxS/3
It consists of 3 parts:
Anything until the first space
anything until the next match, which is
digits, followed by a slash, followed by more digits, followed by whatever remains
I have searched and searched but I cannot find anything quite exactly like what I need. I have a code:
$repeater = "pompom";
if (preg_match('/([a-zA-Z])\1{3}/', $repeater)) {
echo "Yes, $repeater does repeat 3 characters.<br>";
}
else {
echo "No, $repeater does not repeat 3 characters.<br>";
}
(I can barely understand regex as it is... so just ignore my current regex.. it's just a mixture of randomness I began to type.)
Anyhow, I need the regex code to return
true for words like
pompom
grugru
mopmop
cancan
etc...
and return false for words like
coocoo
daadaa
allall
giigii
etc.
The regex must detect and return true for any word that has 3 different characters that repeat more than once in that word.
This must work for words that have characters that are not necessarily in sequence with one another. I have found solutions to that. Words such as "cooo" or "pooool" is not what I need to apply this regex for. Note: This must return True only for words that have 3 or more different letters in the word and are repeated more than once. Such as, pompom..
This should return false for words like coocoo because there are only 2 different letters in the word.
Again, please ignore my current regex it was just what I had when I decided to ask for some help. I've tried probably 200 different methods, all wrong of course :].
Any help would be nice, maybe we can figure this out together I just need some ideas to bounce off of.
The following regex will perform as requested:
^((.)(?!\2)(.)(?!\2)(?!\3).)\1$
https://regex101.com/r/eHKzWB/3
Simple problem but i sux at regular expressions so i need here ur help.
What do i need to type to find a number between two first signs: •
Find out its codes but it doenst help me much: http://www.fileformat.info/info/unicode/char/2022/index.htm
Do you know what should i type in for example preg_match function to make it work?
Example:
• 12345 • TESTTESTTEST
Example Output:
12345
Thanks in advance!
To match a specific Unicode code point, use \x{FFFF} where FFFF is the hexadecimal number of the code point you want to match. You can omit leading zeros in the hexadecimal number between the curly braces. Since \x by itself is not a valid regex token, \x{1234} can never be confused to match \x 1234 times. It always matches the Unicode code point U+1234. \x{1234}{5678} will try to match code point U+1234 exactly 5678 times.
Anyway, what you're probably looking for is something like this:
\x{2022} (\d*) \x{2022}
As for the (\d*) part, it basically means match any digit infinite times, and assign this bit of the pattern as a match (braces stand for capture groups)
Actually i found out a way to do it a bit easier.
I used preg_match() with $pattern = "/[0-9]{1,}/";
Huh xD
I want to validate these phone number formats:
517123123
+48517123123
+48 517 123 123
(48)517123123
(48)517 123 123
517-123-123
48 517-123-123
48/517-123-123
48 517 123 123
I wrote this regex:
(\+?)+(((\(([0-9]+){2,2}\)))|(([0-9]+){2,2})?)+(\/?)+(\s?)+(([0-9]+){9,9}|([0-9]+){3,3}(\s|-){1,1}([0-9]+){3,3}(\s|-){1,1}([0-9]+){3,3})
The problem is that it's makes big numbers like 8978978979878978967 valid. Where is my mistake?
Looking at just the end of the regex, I see something that you seem to be doing in multiple places;
([0-9]+){3,3}
The + says at least one repeat of [0-9], which makes 1111111111111 a perfectly valid match. You then limit it to exactly 3 of those matches, which can still be a very long number.
If you want exactly 3 digits, remove the +.
may be you lost anchors.... however, use my regex ^(\+?(\(\d{2}\)|(\d{2})|(\d{2}[/ ])))?((\d{3} \d{3} \d{3})|(\d{3}-\d{3}-\d{3})|(\d{9}))$
At the moment I can't see what your regex is doing, there is too much superfluous stuff in it.
You have too many groups
You want to repeat optional characters!?
e.g.:
(\+?)+, you don't need a group around and you don't want to repeat that, so \+? is what you want here.
(\s?)+, do you want to say "0 or more whitespaces"? Then \s* is what you need.
When you write e.g. {9,9}, then you can remove one digit, {9} is the same.
You are nesting quantifiers, thats the place where you allow too many characters. You have multiple places, where you do ([0-9]+){9,9}, that means 1 or more digits and repeat that 9 times.
I'm just getting to know regular expressions, but after doing quite a bit of reading (and learning quite a lot), I still have not been able to figure out a good solution to this problem.
Let me be clear, I understand that this particular problem might be better solved not using regular expressions, but for the sake of brevity let me just say that I need to use regular expressions (trust me, I know there are better ways to solve this).
Here's the problem. I'm given a big file, each line of which is exactly 4 characters long.
This is a regex that defines "valid" lines:
"/^[AB][CD][EF][GH]$/m"
In english, each line has either A or B at position 0, either C or D at position 1, either E or F at position 2, and either G or H at position 3. I can assume that each line will be exactly 4 characters long.
What I'm trying to do is given one of those lines, match all other lines that contain 2 or more common characters.
The below example assumes the following:
$line is always a valid format
BigFileOfLines.txt contains only valid lines
Example:
// Matches all other lines in string that share 2 or more characters in common
// with "$line"
function findMatchingLines($line, $subject) {
$regex = "magic regex I'm looking for here";
$matchingLines = array();
preg_match_all($regex, $subject, $matchingLines);
return $matchingLines;
}
// Example Usage
$fileContents = file_get_contents("BigFileOfLines.txt");
$matchingLines = findMatchingLines("ACFG", $fileContents);
/*
* Desired return value (Note: this is an example set, there
* could be more or less than this)
*
* BCEG
* ADFG
* BCFG
* BDFG
*/
One way I know that will work is to have a regex like the following (the following regex would only work for "ACFG":
"/^(?:AC.{2}|.CF.|.{2}FG|A.F.|A.{2}G|.C.G)$/m"
This works alright, performance is acceptable. What bothers me about it though is that I have to generate this based off of $line, where I'd rather have it be ignorant of what the specific parameter is. Also, this solution doesn't scale terrible well if later the code is modified to match say, 3 or more characters, or if the size of each line grows from 4 to 16.
It just feels like there's something remarkably simple that I'm overlooking. Also seems like this could be a duplicate question, but none of the other questions I've looked at really seem to address this particular problem.
Thanks in advance!
Update:
It seems that the norm with Regex answers is for SO users to simply post a regular expression and say "This should work for you."
I think that's kind of a halfway answer. I really want to understand the regular expression, so if you can include in your answer a thorough (within reason) explanation of why that regular expression:
A. Works
B. Is the most efficient (I feel there are a sufficient number of assumptions that can be made about the subject string that a fair amount of optimization can be done).
Of course, if you give an answer that works, and nobody else posts the answer *with* a solution, I'll mark it as the answer :)
Update 2:
Thank you all for the great responses, a lot of helpful information, and a lot of you had valid solutions. I chose the answer I did because after running performance tests, it was the best solution, averaging equal runtimes with the other solutions.
The reasons I favor this answer:
The regular expression given provides excellent scalability for longer lines
The regular expression looks a lot cleaner, and is easier for mere mortals such as myself to interpret.
However, a lot of credit goes to the below answers as well for being very thorough in explaining why their solution is the best. If you've come across this question because it's something you're trying to figure out, please give them all a read, helped me tremendously.
Why don't you just use this regex $regex = "/.*[$line].*[$line].*/m";?
For your example, that translates to $regex = "/.*[ACFG].*[ACFG].*/m";
This is a regex that defines "valid" lines:
/^[A|B]{1}|[C|D]{1}|[E|F]{1}|[G|H]{1}$/m
In english, each line has either A or B at position 0, either C or D
at position 1, either E or F at position 2, and either G or H at
position 3. I can assume that each line will be exactly 4 characters
long.
That's not what that regex means. That regex means that each line has either A or B or a pipe at position 0, C or D or a pipe at position 1, etc; [A|B] means "either 'A' or '|' or 'B'". The '|' only means 'or' outside of character classes.
Also, {1} is a no-op; lacking any quantifier, everything has to appear exactly once. So a correct regex for the above English is this:
/^[AB][CD][EF][GH]$/
or, alternatively:
/^(A|B)(C|D)(E|F)(G|H)$/
That second one has the side effect of capturing the letter in each position, so that the first captured group will tell you whether the first character was A or B, and so on. If you don't want the capturing, you can use non-capture grouping:
/^(?:A|B)(?:C|D)(?:E|F)(?:G|H)$/
But the character-class version is by far the usual way of writing this.
As to your problem, it is ill-suited to regular expressions; by the time you deconstruct the string, stick it back together in the appropriate regex syntax, compile the regex, and do the test, you would probably have been much better off just doing a character-by-character comparison.
I would rewrite your "ACFG" regex thus: /^(?:AC|A.F|A..G|.CF|.C.G|..FG)$/, but that's just appearance; I can't think of a better solution using regex. (Although as Mike Ryan indicated, it would be better still as /^(?:A(?:C|.E|..G))|(?:.C(?:E|.G))|(?:..EG)$/ - but that's still the same solution, just in a more efficiently-processed form.)
You've already answered how to do it with a regex, and noted its shortcomings and inability to scale, so I don't think there's any need to flog the dead horse. Instead, here's a way that'll work without the need for a regex:
function findMatchingLines($line) {
static $file = null;
if( !$file) $file = file("BigFileOfLines.txt");
$search = str_split($line);
foreach($file as $l) {
$test = str_split($l);
$matches = count(array_intersect($search,$test));
if( $matches > 2) // define number of matches required here - optionally make it an argument
return true;
}
// no matches
return false;
}
There are 6 possibilities that at least two characters match out of 4: MM.., M.M., M..M, .MM., .M.M, and ..MM ("M" meaning a match and "." meaning a non-match).
So, you need only to convert your input into a regex that matches any of those possibilities. For an input of ACFG, you would use this:
"/^(AC..|A.F.|A..G|.CF.|.C.G|..FG)$/m"
This, of course, is the conclusion you're already at--so good so far.
The key issue is that Regex isn't a language for comparing two strings, it's a language for comparing a string to a pattern. Thus, either your comparison string must be part of the pattern (which you've already found), or it must be part of the input. The latter method would allow you to use a general-purpose match, but does require you to mangle your input.
function findMatchingLines($line, $subject) {
$regex = "/(?<=^([AB])([CD])([EF])([GH])[.\n]+)"
+ "(\1\2..|\1.\3.|\1..\4|.\2\3.|.\2.\4|..\3\4)/m";
$matchingLines = array();
preg_match_all($regex, $line + "\n" + $subject, $matchingLines);
return $matchingLines;
}
What this function does is pre-pend your input string with the line you want to match against, then uses a pattern that compares each line after the first line (that's the + after [.\n] working) back to the first line's 4 characters.
If you also want to validate those matching lines against the "rules", just replace the . in each pattern to the appropriate character class (\1\2[EF][GH], etc.).
People may be confused by your first regex. You give:
"/^[A|B]{1}|[C|D]{1}|[E|F]{1}|[G|H]{1}$/m"
And then say:
In english, each line has either A or B at position 0, either C or D at position 1, either E or F at position 2, and either G or H at position 3. I can assume that each line will be exactly 4 characters long.
But that's not what that regex means at all.
This is because the | operator has the highest precedence here. So, what that regex really says, in English, is: Either A or | or B in the first position, OR C or | or D in the first position, OR E or | or F in the first position, OR G or '|orH` in the first position.
This is because [A|B] means a character class with one of the three given characters (including the |. And because {1} means one character (it is also completely superfluous and could be dropped), and because the outer | alternate between everything around it. In my English expression above each capitalized OR stands for one of your alternating |'s. (And I started counting positions at 1, not 0 -- I didn't feel like typing the 0th position.)
To get your English description as a regex, you would want:
/^[AB][CD][EF][GH]$/
The regex will go through and check the first position for A or B (in the character class), then check C or D in the next position, etc.
--
EDIT:
You want to test for only two of these four characters matching.
Very Strictly speaking, and picking up from #Mark Reed's answer, the fastest regex (after it's been parsed) is likely to be:
/^(A(C|.E|..G))|(.C(E)|(.G))|(..EG)$/
as compared to:
/^(AC|A.E|A..G|.CE|.C.G|..EG)$/
This is because of how the regex implementation steps through text. You first test if A is in the first position. If that succeeds, then you test the sub-cases. If that fails, then you're done with all those possible cases (or which there are 3). If you don't yet have a match, you then test if C is in the 2nd position. If that succeeds, then you test for the two subcases. And if none of those succeed, you test, `EG in the 3rd and 4th positions.
This regex is specifically created to fail as fast as possible. Listing each case out separately, means to fail, you would have test 6 different cases (each of the six alternatives), instead of 3 cases (at a minimum). And in cases of A not being the first position, you would immediately go to test the 2nd position, without hitting it two more times. Etc.
(Note that I don't know exactly how PHP compiles regex's -- it's possible that they compile to the same internal representation, though I suspect not.)
--
EDIT: On additional point. Fastest regex is a somewhat ambiguous term. Fastest to fail? Fastest to succeed? And given what possible range of sample data of succeeding and failing rows? All of these would have to be clarified to really determine what criteria you mean by fastest.
Here's something that uses Levenshtein distance instead of regex and should be extensible enough for your requirements:
$lines = array_map('rtrim', file('file.txt')); // load file into array removing \n
$common = 2; // number of common characters required
$match = 'ACFG'; // string to match
$matchingLines = array_filter($lines, function ($line) use ($common, $match) {
// error checking here if necessary - $line and $match must be same length
return (levenshtein($line, $match) <= (strlen($line) - $common));
});
var_dump($matchingLines);
I bookmarked the question yesterday in the evening to post an answer today, but seems that I'm a little late ^^ Here is my solution anyways:
/^[^ACFG]*+(?:[ACFG][^ACFG]*+){2}$/m
It looks for two occurrences of one of the ACFG characters surrounded by any other characters. The loop is unrolled and uses possessive quantifiers, to improve performance a bit.
Can be generated using:
function getRegexMatchingNCharactersOfLine($line, $num) {
return "/^[^$line]*+(?:[$line][^$line]*+){$num}$/m";
}