For bioinformatics, it is critical to know how to use at least the basics of regular expressions (regex). There are regex that you use all the time, but most of us will look them up more often than not. Following are some links to online tutorials and cheatsheets to guide you the next time you need to use them (it will probably be sooner than you think!
RegexOne: an interactive tutorial
Regular-Expressions.info. The name says it all! Also has links for grep and other languages (see below).
the command line program grep, which stands for global regular expression print, can search files and folders for patterns, which includes regular expressions.
Using regular expressions in grep
Ryans Tutorial on grep and regex
A fairly comprehensive regex primer for the R language
RStudio.com regex cheatsheet (pdf)
For R tidyverse users, here is a link to R for Data Science chapter section on regex, and here is the stringr package regex page.