Regular expression to check specific substring inside a string

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Hi All,
I have one textbox in an angular application. We want to restrict some set of string from that textbox value. A regular expression check to restrict '&&', '||', '--'. '/*' to be inserted inside that string. I have tried many regular expression but not working.

What I have tried:

I tried many regex like below example
(&&)(--)(__)
(&&)|(--)|(__)
etc..

Posted 13-Jul-21 3:57am

Sunil Kumar Pandab

Updated 13-Jul-21 7:33am

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2 solutions

Solution 2

You can also try this way:

&&|\|\||--|__|/\*

groups are not necessary.

Just a few interesting links to help building and debugging RegEx.
Here is a link to RegEx documentation:
perlre - perldoc.perl.org[^]
Here is links to tools to help build RegEx and debug them:
.NET Regex Tester - Regex Storm[^]
Expresso Regular Expression Tool[^]
RegExr: Learn, Build, & Test RegEx[^]
Online regex tester and debugger: PHP, PCRE, Python, Golang and JavaScript[^]
This one show you the RegEx as a nice graph which is really helpful to understand what is doing a RegEx: Debuggex: Online visual regex tester. JavaScript, Python, and PCRE.[^]
This site also show the Regex in a nice graph but can't test what match the RegEx: Regexper[^]

Posted 13-Jul-21 7:33am

Patrice T

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OriginalGriff · Accepted Answer · 2021-07-13T04:14:00

Solution 1

This worked for me:

(&&)|(\|\|)|(--)|(__)|(/\*)

Bear in mind that that Regex will find those strings - so if you get a match you need to reverse the decision!
To get a match when none of the sequences are there, you'd need to use a negative lookahead:

^(?!.*(&&)|(\|\|)|(--)|(__)|(/\*)).*$

Which ./.. looks pretty impenetrable!

Posted 13-Jul-21 4:14am

OriginalGriff

Updated 13-Jul-21 4:15am

v2

Comments

Maciej Los 13-Jul-21 15:53pm

5ed!

Sunil Kumar Pandab 14-Jul-21 9:18am

Yes your solution is working as expected but ^(?!.*(&&)|(\|\|)|(--)|(__)|(/\*)).*$ all together it's not working. I divided regex to multiple validation like ^(?!.*(&&)).*$ and ^(?!.*(\|\|)).*$ and so on.