Regex for finding valid filename

The regex would be something like (for a three letter extension):

^[^/?*:;{}\\]+\.[^/?*:;{}\\]{3}$

PHP needs backslashes escaped, and preg_match() needs forward slashes escaped, so:

$pattern = "/^[^\\/?*:;{}\\\\]+\\.[^\\/?*:;{}\\\\]{3}$/";

To match filenames like "hosts" or ".htaccess", use this slightly modified expression:

^[^/?*:;{}\\]*\.?[^/?*:;{}\\]+$

Here you go:

"[^/?*:;{}\\]+\\.[^/?*:;{}\\]+"

"One or more characters that aren't any of these ones, then a dot, then some more characters that aren't these ones."

(As long as you're sure that the dot is really required - if not, it's simply: "[^/?*:;{}\\]+"

$a = preg_match('=^[^/?*;:{}\\\\]+\.[^/?*;:{}\\\\]+$=', 'file.abc');

^ ... $ - begin and end of the string
[^ ... ] - matches NOT the listed chars.

Related