How can I replace every instance of a pattern in ruby?

Question

string.sub looks like it only replaces the first instance. Is there an option for that or another method that can replace all patterns? Can you do it inside a regex like perl?

(I think something like r/blah/blah/)

... and +1 to anyone who can tell me WHY ON EARTH does string.sub replace just the FIRST match?

For the same reason that Perl needs a g modifier to make substitutions global. Replace all is often what you want, but not always. — Telemachus
– Telemachus, Commented Dec 13, 2009 at 1:39

Łukasz Rogalski · Accepted Answer · 2016-01-07 19:53:48Z

84

String.gsub should do the trick.

Quoting docs:

gsub(pattern, replacement) → new_str

Returns a copy of str with the all occurrences of pattern substituted for the second argument. The pattern is typically a Regexp; if given as a String, any regular expression metacharacters it contains will be interpreted literally, e.g. \\d will match a backlash followed by d, instead of a digit.

edited Jan 7, 2016 at 19:53

Łukasz Rogalski

23.3k10 gold badges63 silver badges93 bronze badges

answered Dec 13, 2009 at 1:31

Brian Young

1,78813 silver badges11 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

aarona Over a year ago

w00t. Thanks. You would think that sub would do that as a default and then have an int param for replace the first N occurrences!

Robert K Over a year ago

DJ: no you wouldn't. If you want to replace the first match, then SUBstitute is your choice, if not Global SUBstitute is your choice.

Aurélien Bénel Over a year ago

For further reference, here is the manual page.

Gareth · Accepted Answer · 2009-12-13 01:53:42Z

8

I could explain why sub just replaces the first match of a pattern, but I think the documentation does it so much better (from ri String#sub on the command line):

str.sub(pattern, replacement)         => new_str
str.sub(pattern) {|match| block }     => new_str

Returns a copy of _str_ with the _first_ occurrence of _pattern_
replaced with either _replacement_ or the value of the block.

answered Dec 13, 2009 at 1:53

Gareth

139k36 gold badges152 silver badges158 bronze badges

1 Comment

Andrew Arrow Over a year ago

wow, i've been using ruby and rails for years. Today was the 1st time I typed ri something#method because of your post. I had no idea that feature was there! Been just googling the terms and find the docs that way.

Collectives™ on Stack Overflow

How can I replace every instance of a pattern in ruby?

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related