regex - Replace all dots,special characters except for the file extension

Question

I want a regex in such a way that to replace the filename which contains special characters and dots(.) etc. with underscore(_) except the extension of the filename.

Help me with an regex

Answer 1

try this:

([!@#$%^&*()]|(?:[.](?![a-z0-9]+$)))

with the insensitive flag "i". Replace with '_'

The first lot of characters can be customised, or maybe use \W (any non-word)

so this reads as:

replace with '_' where I match and of this set, or a period that is not followed by some characters or numbers and the end of line

Sample c# code:

var newstr = new Regex("([!@#$%^&*()]|(?:[.](?![a-z0-9]+$)))", RegexOptions.IgnoreCase)
    .Replace(myPath, "_");

Answer 2

Since you only care about the extension, forget about the rest of the filename. Write a regex to scrape off the extension, discarding the original filename, and then glue that extension onto the new filename.

This regular expression will match the extension, including the dot.: \.[^.]*$