Regular Expressions 101

^start of line

Negative Lookahead(?!.*?-\d+[xX]\d+)

.*?any character (except for line terminators), repeated any number of times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\d+a digit, repeated at least once

Character Class[xX]

xthe literal x (120₁₀ / 170₈ / 78₁₆) (case sensitive)

Xthe literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive)

\d+a digit, repeated at least once

Group 1(.*)

.*any character (except for line terminators), repeated any number of times

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^(?!.*?-\d+[xX]\d+)(.*)$

New

somefile.txt
another-67x22.img
-667x92.jpg
goodfile.pdf