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Build your own grep

Learn about regex syntax: character classes, quantifiers and more

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Build your own grep

Build your own grep is free this October.

The core challenge experience is completely free this month. If you'd like to enjoy advanced features such as running turbo tests, dark mode, or unlimited code examples, you'll need a membership.

Start free challenge → View Membership Plans →

Regular expressions (or Regexes) are patterns used to match character combinations in strings. In this challenge, you'll build a Regex engine from scratch by recreating grep, a CLI tool for regex-based searching.

Along the way you'll learn about Regex syntax, character classes, quantifiers and more.

Stages

Match a literal character

Match word characters

Positive Character Groups

Negative Character Groups

Combining Character Classes

Start of string anchor

End of string anchor

Match one or more times

Match zero or one times

Backreferences

Single Backreference

Multiple Backreferences

Nested Backreferences

File Search

Search a single-line file

Search a multi-line file

Search multiple files

Recursive search

Quantifiers

Match zero or more times

Match exactly n times

Match at least n times

Match between n and m times

RECENT ATTEMPTS 0

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