CODEWITHSUNDEEP
regex
Ahmet Altun
Ahmet Altun

Reputation: 4049

Regex - Pattern Matching & Replace

Text is: "R1 AND R24 OR R456'

I want to write a pattern that can find R and the numbers (only numbers) following it. So the matches will be: R1, R24, R456.

How can I write appropriate regex?

Upvotes: 0

Views: 201

Answers (4)

Flinsch
Flinsch

Reputation: 4339

The topic of your question says "Replace" but I can't find any points concerning possible replacement in your question.

The regex pattern /R[0-9]+/ should work to find "R1", "R24", and "R456" in "R1 AND R24 OR R456".

To extract the numbers following the respective "R" you can add a group to the regex pattern: /R([0-9]+)/. Then you can just "match" the test string against the regex pattern and extract group 1 for each match:

Target String: R1 AND R24 OR R456
Regex Pattern: R([0-9]+)
"find next"; group(0): R1; group(1): 1
"find next"; group(0): R24; group(1): 24
"find next"; group(0): R456; group(1): 456
"find next"; null

Which programming language are you using? We could then provide an even concreter example.

Upvotes: 0

Jack V.
Jack V.

Reputation: 1381

/R\d+/

  • /.../ represents a regex (you don't type them in all languages)
  • R represents a literal character R
  • \d represents a digit

  • \d+ represents "one or more" of whatever \d represents

  • As other people pointed out, you can use \b to represent a "beginning of word" if you want to avoid matching the end of words like "thumb2"

  • You can replace by doing something like s/R(\d+)/rev_\1/g to turn R132 into rev_132 all through the text

  • The exact syntax of how to apply a regex varies from language to language: in Perl, you type something very like the /.../ syntax above. In other languages, you may use a string "R\d+" passed to a function. In some you need the slashes inside a string.

  • You can test it online, eg: http://www.fileformat.info/tool/regex.htm

  • There are many online introductions, eg: http://www.regular-expressions.info/reference.html

Upvotes: 1

stema
stema

Reputation: 93046

Something like

\bR\d+

See it here on Regexr

\b is a anchor for a word boundary, that means here there can be no word character (letter, number and _) before the R

\d is a digit

+ one or more

If you want to replace the numbers you can do so (if your language supports lookbehinds)

(?<=\bR)\d+

See here on Regexr

For the correct syntax you need to tell us your language.

Upvotes: 2

Qtax
Qtax

Reputation: 33928

The regex would be \bR\d+. To also capture the number you can use \bR(\d+).

Upvotes: 1

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