Replace All Chars With #, Except for Last 4

var input = "123456789";var output = input.replace(/.(?=.{4})/g, '*');console.log(output);

Replacing last 4 characters with a "*"

A quick and easy method...

public static String replaceLastFour(String s) {
    int length = s.length();
    //Check whether or not the string contains at least four characters; if not, this method is useless
    if (length < 4) return "Error: The provided string is not greater than four characters long.";
    return s.substring(0, length - 4) + "****";
}

Now all you have to do is call replaceLastFour(String s) with a string as the argument, like so:

public class Test {
    public static void main(String[] args) {
        replaceLastFour("hi");
        //"Error: The provided string is not greater than four characters long."
        replaceLastFour("Welcome to StackOverflow!");
        //"Welcome to StackOverf****"
    }

    public static String replaceLastFour(String s) {
        int length = s.length();
        if (length < 4) return "Error: The provided string is not greater than four characters long.";
        return s.substring(0, length - 4) + "****";
    }
}

How to replace all characters but for the first and last two with gsub Ruby

**If you want to mask with a fixed number of * symbols, you may yse

'lorem.ipsum@gmail.com'.sub(/\A(..).*@.*(..)\z/, '\1****@****\2')
# => lo****@****om

See the Ruby demo.

Here,

• \A - start of string anchor
• (..) - Group 1: first 2 chars
• .*@.* - any 0+ chars other than line break chars as many as possible up to the last @ followed with another set of 0+ chars other than line break ones
• (..) - Group 2: last 2 chars
• \z - end of string.

The \1 in the replacment string refers to the value kept in Group 1, and \2 references the value in Group 2.

If you want to mask existing chars while keeping their number, you might consider an approach to capture the parts of the string you need to keep or process, and manipulate the captures inside a sub block:

'lorem.ipsum@gmail.com'.sub(/\A(..)(.*)@(.*)(..)\z/) { 
    $1 + "*"*$2.length + "@" + "*"*$3.length + $4
}
# => lo*********@*******om

See the Ruby demo

Details

• \A - start of string
• (..) - Group 1 capturing any 2 chars
• (.*) - Group 2 capturing any 0+ chars as many as possible up to the last....
• @ - @ char
• (.*) - Group 3 capturing any 0+ chars as many as possible up to the
• (..) - Group 4: last two chars
• \z - end of string.

Note that inside the block, $1 contains Group 1 value, $2 holds Group 2 value, and so on.

PHP remove all characters before, except last number

preg_match('/(\d+)\.ts$/', $test, $matches);
echo $matches[1];

How to substitute all characters in a string except for some (in Ruby)

Here's a different approach. First, do the reverse of what you ultimately want: redact what you want to keep. Then compare this redacted string to your original character by character, and if the characters are the same, redact, and if they are not, keep the original.

class String
  # Returns a string with all words except those passed in as keepers
  # redacted.
  #
  #      "Part of this string needs to be substituted".gsub_except(["this string", "substituted"], '*')
  #      # => "**** ** this string ***** ** ** substituted"
  def gsub_except keep, mark
    reverse_keep = self.dup
    keep.each_with_object(Hash.new(0)) { |e, a| a[e] = mark * e.length }
             .each { |word, redacted| reverse_keep.gsub! word, redacted }
    reverse_keep.chars.zip(self.chars).map do |redacted, original|
      redacted == original && original != ' ' ?  mark : original
    end.join
  end
end

Replace all the _ except one before last one

Use this (corrected now!)

<?php
$subject = 'http://distilleryimage3_s3_amazonaws_com/8af11cdcf11e286b022000ae90285_7_jpg';
$pattern = '/(_)(?!\d_jpg)/';


var_dump(preg_replace($pattern, '.', $subject));

This outputs

http://distilleryimage3.s3.amazonaws.com/8af11cdcf11e286b022000ae90285_7.jpg

How to replace some characters with asterisks except first four characters

Using substr() you do this.

PHP

<?php        
    function hide_mail($email) {
        $new_mail = "";
        $mail_part1 = explode("@", $email);
        $mail_part2 = substr($mail_part1[0],4); // Sub string after fourth character.
        $new_mail = substr($mail_part1[0],0,4); // Add first four character part.
        $new_mail .= str_repeat("*", strlen($mail_part2))."@"; // Replace *. And add @
        $new_mail .= $mail_part1[1]; // Add last part.
        return $new_mail;
    }

    echo hide_mail("example@gmail.com");
?>

Output

exam***@gmail.com

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