# Regex Injection

[Regular expressions ( **regex**) are often used in web-development to describe which characters appear in a string, and how they are ordered.](/content/lessons/regex-injection/the-uses-of-regex/index.html)

| ab **c*** | matches a string that has ab followed by zero or more c's |
| ab **c+** | matches a string that has ab followed by one or more c's |
| ab **c?** | matches a string that has ab followed by zero or one c's |
| ab **c2** | matches a string that has ab followed by cc |
| ab **c{2,}** | matches a string that has ab followed by 2 or more c's |
| ab **c{2,5}** | matches a string that has ab followed by 2 up to 5 c's |
| a **(bc)*** | matches a string that has a followed by zero or more copies of the sequence bc's |
| a **(bc){2,5}** | matches a string that has a followed by 2 up to 5 copies of the sequence bc's |