noun

regex

REJ-eks

Regex (noun) means a short line of symbols that describes a pattern of text, used to find, check or replace pieces of writing that match that pattern; short for regular expression. Example: “He wrote a regex to pull every date out of the log file.”

noun

A short line of symbols that describes a pattern of text, used to find, check or replace pieces of writing that match that pattern; short for regular expression.

"He wrote a regex to pull every date out of the log file."

"A simple regex will tell you whether the field contains only digits."

computing The notation itself, taken as a whole: the set of rules by which such patterns are written.

"Regex differs slightly between programming languages, so a pattern that works in one may need adjusting in another."

How to Use Regex

Learner’s notes

In plain EnglishA pattern that describes what text should look like so a computer can find or check it.

When to use it

Technical and informal; regular expression is the formal term used in documentation.

Memory tip

The plural is usually regexes; regexen appears as a jokey form among programmers.

Trace the full origin ↓

Easily confused with

wildcard glob → regular expression string →

Common pairings

write a regex regex pattern match a regex regex replace

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Fill the Gap

Can you complete this real example?

He wrote a _____ to pull every date out of the log file.

Etymology

A shortening of regular expression.

Origin: English

Synonyms

View more →

regular expression pattern search pattern regexp regular expression syntax pattern syntax

Related Words

order design model figure practice cycle convention pattern

Frequently Asked Questions

What is the difference between a regex and an ordinary search?

An ordinary search looks for the exact characters you typed. A regex describes a shape of text instead, so one pattern can match anything that fits the description, such as any five-digit number or any word ending in ing.

Is regex a programming language?

No. It is a notation for describing text patterns, used inside programming languages, editors and command-line tools. On its own it cannot store values or perform general computation the way a programming language can.

How is regex pronounced?

Most commonly REJ-eks, with a soft g, although REG-eks with a hard g is also heard. Both are widely understood, and the full form regular expression is unambiguous.

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