I'm trying to validate a telephone number which should contain only digits with some special characters like () , - . I've tried the following /^[0-9,()-]+$/ but it is showing an error. The special characters are optional, other than those special characters and digits are not allowed.
I'd suggest you take a look at Perl's RegEx tutorial and www.regular-expressions.info for a better understanding of RegEx's.
The pattern you have provided (even if syntactically corrected) is not appropriate for your case (phone numbers), as it matches strings like 78,(-34.
The first step to write a correct RegEx is understanding the pattern you need. For your case, you have to think about the different strings that will match as a phone number. Some examples:
Match:
(500)-8764531
500-8764531
(+9821)-76787600
76787600,01
No match
(500)-876453187645318764531
500,8764531
(+9821-76787600
76787600,01)
The next step is to build a RegEx that matches those patterns. After that you have to test your pattern with different boundary cases and if required do the previous steps again.
Related
As the title says, I'm trying to build up a regular expression that can recognize strings with this format:
word!!cat!!DOG!! ... Phone!!home!!
where !! is used as a delimiter. Each word must have a length between 1 and 5 characters. Empty words are not allowed, i.e. no strings like !!,!!!! etc.
A word can only contain alphabetical characters between a and z (case insensitive). After each word I expect to find the special delimiter !!.
I came up with the solution below but since I need to add other controls (e.g. words can contain spaces) I would like to know if I'm on the right way.
(([a-zA-Z]{1,5})([!]{2}))+
Also note that empty strings are not allowed, hence the use of +
Help and advices are very welcome since I just started learning how to build regular expressions. I run some tests using http://regexr.com/ and it seems to be okay but I want to be sure. Thank you!
Examples that shouldn't match:
a!!b!!aaaaaa!!
a123!!b!!c!!
aAaa!!bbb
aAaa!!bbb!
Splitting the string and using the values between the !!
It depends on what you want to do with the regular expression. If you want to match the values between the !!, here are two ways:
Matching with groups
([^!]+)!!
[^!]+ requires at least 1 character other than !
!! instead of [!]{2} because it is the same but much more readable
Matching with lookahead
If you only want to match the actual word (and not the two !), you can do this by using a positive lookahead:
[^!]+(?=!!)
(?=) is a positive lookahead. It requires everything inside, i.e. here !!, to be directly after the previous match. It however won't be in the resulting match.
Here is a live example.
Validating the string
If you however want to check the validity of the whole string, then you need something like this:
^([^!]+!!)+$
^ start of the string
$ end of the string
It requires the whole string to contain only ([^!]+!!) one or more than one times.
If [^!] does not fit your requirements, you can of course replace it with [a-zA-Z] or similar.
I am trying to find the appropriate regex pattern that allows me to pick out whole words either starting with or ending with a comma, but leave out numbers. I've come up with ([\w]+,) which matches the first word followed by a comma, so in something like:
red,1,yellow,4
red, will match, but I am trying to find a solution that will match like like the following:
red, 1 ,yellow, 4
I haven't been able to find anything that can break strings up like this, but hopefully you'll be able to help!
This regex
,?[a-zA-Z][a-zA-Z0-9]*,?
Matches 'words' optionally enclose with commas. No spaces between commas and the 'word' are permitted and the word must start with an alphanumeric.
See here for a demo.
To ascertain that at least one comma is matched, use the alternation syntax:
(,[a-zA-Z][a-zA-Z0-9]*|[a-zA-Z][a-zA-Z0-9]*,)
Unfortunately no regex engine that i am aware of supports cascaded matching. However, since you usually operate with regexen in the context of programming environments, you could repeatedly match against a regex and take the matched substring for further matches. This can be achieved by chaining or iterated function calls using speical delimiter chars (which must be guaranteed not to occur in the test strings).
Example (Javascript):
"red, 1 ,yellow, 4, red1, 1yellow yellow"
.replace(/(,?[a-zA-Z][a-zA-Z0-9]*,?)/g, "<$1>")
.replace(/<[^,>]+>/g, "")
.replace(/>[^>]+(<|$)/g, "> $1")
.replace(/^[^<]+</g, "<")
In this example, the (simple) regex is tested for first. The call returns a sequence of preliminary matches delimted by angle brackets. Matches that do not contain the required substring (, in this case) are eliminated, as is all intervening material.
This technique might produce code that is easier to maintain than a complicated regex.
However, as a rule of thumb, if your regex gets too complicated to be easily maintained, a good guess is that it hasn't been the right tool in the first place (Many engines provide the x matching modifier that allows you to intersperse whitespace - namely line breaks and spaces - and comments at will).
The issue with your expression is that:
- \w resolves to this: [a-zA-Z0-9_]. This includes numeric data which you do not want.
- You have the comma at the end, this will match foo, but not ,foo.
To fix this, you can do something like so: (,\s*[a-z]+)|([a-z]+\s*,). An example is available here.
Recently I'm writing/testing regexps on https://regex101.com/.
My question is: Is it possible to do a positive look-ahead AND a replacement in the same "replacement"? Or just limited kind of replacement is possible.
Input is several lines with phone numbers. Let's say the correct phone number where the number of "numbers" are 11. No matter how the numbers are divided/group together with - / characters, no matter if starts with + 00 or it is omitted.
Some example lines:
+48301234567
+48/30/1234567
+48-30-12-345-67
+483011223344556677
0048301234567
+(48)30/1234567
Positive look-ahead able to check if from the beginning until the end of line there are only 11 digits, regardless how many other, above specified character separating them. This works perfectly.
Where the positive look-ahead check is fine, I would like to delete every character but numbers. The replacement works fine until I'm not involving look-ahead.
Checking the regexp itself working perfectly ("gm" modes):
^(?:\+|00)?(?:[\-\/\(\)]?\d){11}$
Checking the replace part works perfectly (replace to nothing):
[^\d\n]
Put this into look-ahead, after the deletion of non new-line and non-digit characters from the matching lines:
(?=^(?:\+|00)?(?:[\-\/\(\)]?\d){11}$)[^\d\n]
Even I put the ^ $ into look-ahead, seems the replacement working only from beginning of the lines until the very first digit.
I know in real life the replacement and the check should/would go separate ways, however I'm curious if I could mix look-ahead/look-behind with string operations like replace, delete, take the string apart and put together as I like.
UPDATE: This is what would do the trick, however I feel this one "ugly" a bit. Is there any prettier solution?
https://regex101.com/r/yT5dA4/2
Or the version which I asked originally, where only digits remains: regex101.com/r/yT5dA4/3
You cannot replace/delete text with regex. Regex is just a tool for matching certain strings and then taking certain action depending on the matching text, eg. perform a substitution, retrieve the second capture group.
However it is possible to perform certain decisions within a regex engine, by using conditionals. The common syntax for this, with a lookahead assertion, is (?(?=regex)then|else).
With conditionals you can change the behaviour depending on how the text matches the regex. For your example you could do something like:
^(\+)?(?(1)\(|\d)
If the phone number starts with a plus it must be followed by a bracket, else it should start with a digit. Although in your situation, this is not very useful.
If you want to read up more on conditionals in regex you can do so here.
I've got this RegEx example: http://regexr.com?34hihsvn
I'm wondering if there's a more elegant way of writing it, or perhaps a more optimised way?
Here are the rules:
Digits and dashes only.
Must not contain more than 10 digits.
Must have two hyphens.
Must have at least one digit between each hyphen.
Last number must only be one digit.
I'm new to this so would appreciate any hints or tips.
In case the link expires, the text to search is
----------
22-22-1
22-22-22
333-333-1
333-4444-1
4444-4444-1
4444-55555-1
55555-4444-1
666666-7777777-1
88888888-88888888-1
1-1-1
88888888-88888888-22
22-333-
333-22
----------
My regex is: \b((\d{1,4}-\d{1,5})|(\d{1,5}-\d{1,4}))-\d{1}\b
I'm using this site for testing: http://gskinner.com/RegExr/
Thanks for any help,
Nick
Here is a regex I came up with:
(?=\b[\d-]{3,10}-\d\b)\b\d+-\d+-\d\b
This uses a look-ahead to validate the information before attempting the match. So it looks for between 3-10 characters in the class of [\d-] followed by a dash and a digit. And then after that you have the actual match to confirm that the format of your string is actually digit(dash)digit(dash)digit.
From your sample strings this regex matches:
22-22-1
333-333-1
333-4444-1
4444-4444-1
4444-55555-1
55555-4444-1
1-1-1
It also matches the following strings:
22-7777777-1
1-88888888-1
Your regexp only allows a first and second group of digits with a maximum length of 5. Therefore, valid strings like 1-12345678-1 or 123456-1-1 won't be matched.
This regexp works for the given requirements:
\b(?:\d\-\d{1,8}|\d{2}\-\d{1,7}|\d{3}\-\d{1,6}|\d{4}\-\d{1,5}|\d{5}\-\d{1,4}|\d{6}\-\d{1,3}|\d{7}\-\d{1,2}|\d{8}\-\d)\-\d\b
(RegExr)
You can use this with the m modifier (switch the multiline mode on):
^\d(?!.{12})\d*-\d+-\d$
or this one without the m modifier:
\b\d(?!.{12})\d*-\d+-\d\b
By design these two patterns match at least three digits separated by hyphens (so no need to put a {5,n} quantifier somewhere, it's useless).
Patterns are also build to fail faster:
I have chosen to start them with a digit \d, this way each beginning of a line or word-boundary not followed by a digit is immediately discarded. Other thing, using only one digit, I know the remaining string length.
Then I test the upper limit of the string length with a negative lookahead that test if there is one more character than the maximum length (if there are 12 characters at this position, there are 13 characters at least in the string). No need to use more descriptive that the dot meta-character here, the goal is to quickly test the length.
finally, I describe the end of string without doing something particular. That is probably the slower part of the pattern, but it doesn't matter since the overwhelming majority of unnecessary positions have already been discarded.
I am trying to form a regular expression that will match strings that do NOT end a with a DOT FOLLOWED BY NUMBER.
eg.
abcd1
abcdf12
abcdf124
abcd1.0
abcd1.134
abcdf12.13
abcdf124.2
abcdf124.21
I want to match first three.
I tried modifying this post but it didn't work for me as the number may have variable length.
Can someone help?
You can use something like this:
^((?!\.[\d]+)[\w.])+$
It anchors at the start and end of a line. It basically says:
Anchor at the start of the line
DO NOT match the pattern .NUMBERS
Take every letter, digit, etc, unless we hit the pattern above
Anchor at the end of the line
So, this pattern matches this (no dot then number):
This.Is.Your.Pattern or This.Is.Your.Pattern2012
However it won't match this (dot before the number):
This.Is.Your.Pattern.2012
EDIT: In response to Wiseguy's comment, you can use this:
^((?!\.[\d]+$)[\w.])+$ - which provides an anchor after the number. Therefore, it must be a dot, then only a number at the end... not that you specified that in your question..
If you can relax your restrictions a bit, you may try using this (extended) regular expression:
^[^.]*.?[^0-9]*$
You may omit anchoring metasymbols ^ and $ if you're using function/tool that matches against whole string.
Explanation: This regex allows any symbols except dot until (optional) dot is found, after which all non-numerical symbols are allowed. It won't work for numbers in improper format, like in string: abcd1...3 or abcd1.fdfd2. It also won't work correctly for some string with multiple dots, like abcd.ab123cd.a (the problem description is a bit ambigous).
Philosophical explanation: When using regular expressions, often you don't need to do exactly what your task seems to be, etc. So even simple regex will do the job. An abstract example: you have a file with lines are either numbers, or some complicated names(without digits), and say, you want to filter out all numbers, then simple filtering by [^0-9] - grep '^[0-9]' will do the job.
But if your task is more complex and requires validation of format and doing other fancy stuff on data, why not use a simple script(say, in awk, python, perl or other language)? Or a short "hand-written" function, if you're implementing stand-alone application. Regexes are cool, but they are often not the right tool to use.
I would just use a simple negative look-behind anchored at the end:
.*(?<!\\.\\d+)$