User Input + Ruby + Regex?

Question

I want to give users a text area where they can enter text. Later I will match that input against a different input and extract it if matched.

Flow:

User enters text with returns into a text area
Text is saved in the db in a text field

Then I use the following to extract:

text_reply = text_reply.sub(/#{user.text_to_extract}/m, '').strip

Problem is that it appears that characters like new lines or pipes | are breaking it. As input that we want to match against can look like this:

XXXXXX

XXXXXX
XXXX & XXXXX
asdasd: 123312321 | dasasddsadasads

http://yahoo.com

Suggestions? Thansk

A simple string replace won't do?

Dogbert
– Dogbert

2011-03-22 19:08:52 +00:00
Commented Mar 22, 2011 at 19:08 — Dogbert
– Dogbert, Commented Mar 22, 2011 at 19:08

Andrew · Accepted Answer · 2014-02-05 00:38:59Z

15

You need to escape the input: http://www.ruby-doc.org/core/classes/Regexp.html

See the method escape.

 Regexp.escape(your_input)

edited Feb 5, 2014 at 0:38

Andrew

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answered Mar 22, 2011 at 19:07

Michael Papile

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5 Comments

AnApprentice Over a year ago

Thanks but how do I escape when I do inputtext.split(regex_to_use).first ?

Michael Papile Over a year ago

You do the same thing to that regex if you are taking in user/string input for the regex. Use Regex.escape for any string that may have regex special characters that you do not want to be interpreted as so by the regex engine.

AnApprentice Over a year ago

I don't think this is the issue. It appears to be a | pipe in the input that break s it.

Michael Papile Over a year ago

Yes which is exactly what escaping it avoids. A pipe is a special character in regexes

user1228 Over a year ago

@AnApprentice: Since you discovered the error here, you can select this as the correct answer and close out this question.

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