I use regex101 every time I want write a new regex.
Small tip, regex101 has night mode.
.* = will select all occurrences
A regex is useful for validating simple patterns and for finding patterns in text. For anything beyond that it’s almost certainly a terrible choice.
Learn regex - Great reference.
RegexOne - Learn Regular Expressions with simple, interactive exercises.
Regular Expression in Python HOWTO - Good intro.
Hyperscan - High-performance regular expression matching library.
Oniguruma - Modern and flexible regular expressions library.
RegExr - Learn, Build & Test RegEx.
Regex Tester - Visual regex tester.
grex - Command-line tool and library for generating regular expressions from user-provided test cases.
regHEX - Magical sticky regex-based parser generator.
tiny-regex-c - Small portable regex in C.
libfsm - DFA regular expression library & friends.