Regex: ignore case sensitivity

Question

How can I make the following regex ignore case sensitivity? It should match all the correct characters but ignore whether they are lower or uppercase.

G[a-b]         


        

Answer 1

Depends on implementation but I would use

(?i)G[a-b].

VARIATIONS:

(?i) case-insensitive mode ON    
(?-i) case-insensitive mode OFF

Modern regex flavors allow you to apply modifiers to only part of the regular expression. If you insert the modifier (?im) in the middle of the regex then the modifier only applies to the part of the regex to the right of the modifier. With these flavors, you can turn off modes by preceding them with a minus sign (?-i).

Description is from the page: https://www.regular-expressions.info/modifiers.html

Answer 2

You also can lead your initial string, which you are going to check for pattern matching, to lower case. And using in your pattern lower case symbols respectively .

Answer 3

Addition to the already-accepted answers:

Grep usage:

Note that for greping it is simply the addition of the -i modifier. Ex: grep -rni regular_expression to search for this 'regular_expression' 'r'ecursively, case 'i'nsensitive, showing line 'n'umbers in the result.

Also, here's a great tool for verifying regular expressions: https://regex101.com/

Ex: See the expression and Explanation in this image.

References:

• man pages (man grep)
• http://droptips.com/using-grep-and-ignoring-case-case-insensitive-grep

Answer 4

[gG][aAbB].* probably simples solution if the pattern is not too complicated or long.

Answer 5

C#

using System.Text.RegularExpressions;
...    
Regex.Match(
    input: "Check This String",
    pattern: "Regex Pattern",
    options: RegexOptions.IgnoreCase)

specifically: options: RegexOptions.IgnoreCase

Answer 6

The i flag is normally used for case insensitivity. You don't give a language here, but it'll probably be something like /G[ab].*/i or /(?i)G[ab].*/.