How to check if a RegEx matches all the target string?

Question

I need to check if a regex pattern matches with all the target string.

For example, if the pattern is '[0-9]+':

Target string '123' should result True
Target string '123' + sLineBreak should result False

The code should looks like the following:

uses
  System.RegularExpressions;

begin
  if(TRegEx.IsFullMatch('123' + sLineBreak, '[0-9]+'))
  then ShowMessage('Match all')
  else ShowMessage('Not match all');
end;

I've tried TRegEx.Match(...).Success and TRegEx.IsMatch without success and I'm wondering if there is an easy way for checking if a pattern matches the whole target string.

I've also tried using ^ - start of line and $ - end of line but without any success.

uses
  System.RegularExpressions;

begin
  if(TRegEx.IsMatch('123' + sLineBreak, '^[0-9]+$'))
  then ShowMessage('Match all')
  else ShowMessage('Not match all');
end;

Here you can find an online test demonstrating that if the target string ends with a new line, the regex still matches even using start/end of line.

@Thefourthbird: Yes but it doesn't always work, I've updated the example in the question — Fabrizio, Oct 21 '20 at 12:21
[Strings Ending with a Line Break](https://www.regular-expressions.info/anchors.html) part explains why you should use `\z` instead of `$` to avoid getting match in the last example. — BrakNicku, Oct 21 '20 at 14:44

Ryszard Czech · Accepted Answer · 2020-10-21T21:48:35.250

1

Make sure the whole string matches:

\A[0-9]+\z

Explanation

--------------------------------------------------------------------------------
  \A                       the beginning of the string
--------------------------------------------------------------------------------
  [0-9]+                   any character of: '0' to '9' (1 or more
                           times (matching the most amount possible))
--------------------------------------------------------------------------------
  \z                       the end of the string

Also, see Whats the difference between \z and \Z in a regular expression and when and how do I use it?

edited Oct 21 '20 at 21:48

answered Oct 21 '20 at 21:42

Ryszard Czech

18,032
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Which is the difference between `\A` and `^` ? – Fabrizio Oct 22 '20 at 12:28
1

I found the answer [here](https://stackoverflow.com/a/4250094/4528159). +1 and thanks for your answer – Fabrizio Oct 22 '20 at 12:34

Shekhar Khairnar · Answer 2 · 2020-10-21T13:23:06.707

-5

var str = '123';
var sLineBreak = '\n';

console.log(str.match(/^\d+$/)); //123
console.log((str + 'b').match(/^\d+$/)); //123b
console.log((str + sLineBreak).match(/^\d+$/)); //123\n

You can use : ^\d+$

^ start of string

\d+ at lease one or more number of digits

$ end of string

edited Oct 21 '20 at 13:23

answered Oct 21 '20 at 11:05

Shekhar Khairnar

2,643
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When at least one must occur (as per `+`) you can't say "any". – AmigoJack Oct 21 '20 at 11:37
Unfortunately, the regex still matches if the target string ends with a new line, I've updated the question by also adding an online test – Fabrizio Oct 21 '20 at 12:34
5

That's not Delphi. – Andreas Rejbrand Oct 21 '20 at 12:59

How to check if a RegEx matches all the target string?

2 Answers2