How to Match an Entire String With a Regex

Match exact string

Use the start and end delimiters: ^abc$

How to match the whole string in RegEx?

For second task(number_number) you can use [^a-zA-Z]\d.*_\d.*, in you example asdf894343_84939, you get 894343_84939, or if you want to get only one digit - remove .* after \d.

In your first task, you also may use \d.*/\d[^\s], for example, if you have 34/45 sss - you get 34/45. If you want to get result from whole string you must use in you pattern: ^your pattern$

How do I match an entire string with a regex?

Try the following regular expression:

^Red October$

By default, regular expressions are case sensitive. The ^ marks the start of the matching text and $ the end.

Regex matching the entire string and nothing else

You probably forgot to put ^ at the start of the pattern and $ at the end of it..

..but if you're searching for an exact string, just use == or .Equals - regex is an unnecessary performance hit.

If you mean that you have a document full of words and you want "whole word" style searching, use \b before and after the pattern:

var input = "This is a test that is testing latest regex attempts";
var r = new Regex(@"\btest\b");
r.IsMatch(input); //true

input = "Now I attest we're testing non whole word tests";
r.IsMatch(input); //false

The \b means "word boundary" and is conceptually things like "start of input", "whitespace", "punctuation" etc so putting at the start and end of "test" means that if the document contains "test" it matches but it doesn't match "attest" or "testing"

How to regex match entire string instead of a single character

You need to add ^ and $ anchors to the regular expression, as well as a + to allow multiple characters.

Try this:

/^[\u0600-\u06FF]+$/

I'm not sure if "Arabic spaces" that you mentioned are included in the character range there, but if you want to allow white space in the string then just add a \s inside the [] brackets.

How to check if regex matches whole string in javascript?

You can either compare the length of the source to the match or compare the matched string to the source, if they are the same, you matched the entire string, and not just a part of it:

let source1 = "foo bar 12345";let source2 = "foo bar 12345 foo";
let match1 = source1.match(/foo bar \d+/);let match2 = source2.match(/foo bar \d+/);
console.log(match1[0] === source1);console.log(match1[0].length === source1.length);
console.log(match2[0] === source2);console.log(match2[0].length === source2.length);

Match entire string with regex

Your regex has this shape: ^A|B$.
It seems you didn't expect that this will match Agibberish and gibberishB, and you're actually looking for ^(A|B)$.
Written this way,
it will only match A or B,
it will not match Agibberish and gibberishB.

Btw this part of the regex looks like a bug: [AZa-z].
You probably meant [A-Za-z].

And in fact all alphabetic letters in the regex appear in both upper- and lowercase forms. So you could simplify by quite bit if you add the i flag and eliminate one of the cases:

const postcodeRegex = /^((gir 0a{2})|((([a-z][0-9]{1,2})|(([a-z][a-hj-y][0-9]{1,2})|(([a-z][0-9][a-z])|([a-z][a-hj-y][0-9]?[a-z]))))[0-9][a-z]{2}))$/gi;

Regex match for whole string (not substring) in bash

You need to anchor your regex:

#!/bin/bash

re="^(a|b)$"
if [[ "$1" =~ $re ]]; then
    echo "match!"
else
    echo "no!"
fi

btw this doesn't require regex. You can just use equality using glob pattern as:

if [[ "$1" == [ab] ]]; then
    echo "match!"
else
    echo "no!"
fi

Python regex match whole string only

You can use \Z:

\Z

Matches only at the end of the string.

In [5]: re.match(r'\w+\Z', 'foo\n')

In [6]: re.match(r'\w+\Z', 'foo')
Out[6]: <_sre.SRE_Match object; span=(0, 3), match='foo'>

Regular expression matching for entire string

You can create your character class by using square brackets. So [abc] would match any of the characters inside the class (the brackets).

To get a series of them, you need a quantifier. You already used the + that means one or more. If you also want to allow the empty string, you can use the * meaning zero or more.

To ensure that you are checking the complete string you need anchors. ^ would match the start of the string and $ the end of the string.

^[abc]+$

This regex would match if the complete string consists only of abc and has at least one character.

You can test regexes online e.g. on Regexr. You can see this regex here and of course modify it.