Fetching the substring contained between two specific words

Question

I wanted to know how to proceed when I am interested in the text contained between particular words using ruby. eg.

@var = "Hi, I want to extract container_start ONLY THIS DYNAMIC CONTENT container_end from the message contained between the container_start and container_end "

Now I want to extract the CAPITALIZED content from the string i.e. dynamic but always contained within the two containers (container_start and container_end)

if you look into html tag matcher regex, you will probably know how to grab it. — HungryCoder, Nov 02 '12 at 10:29
http://stackoverflow.com/questions/4115115/extract-substring-from-string-ruby (modify it to suit your needs) — Anand Shah, Nov 02 '12 at 10:38

score 17 · Accepted Answer · answered Nov 02 '12 at 10:37

17

Simple regular expression would do:

@var = "Hi, I want to extract container_start **ONLY THIS DYNAMIC CONTENT** container_end from the message contained between the container_start and container_end "
@var[/container_start(.*?)container_end/, 1] # => " **ONLY THIS DYNAMIC CONTENT** "

answered Nov 02 '12 at 10:37

Victor Deryagin

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Thanks for the answer, it was a BANG ON. – Nishutosh Sharma Nov 02 '12 at 10:43
If I hadn't found this post (or a similar post), how would I have found this answer? This strikes me as a solution which isn't very intuitive. Just curious. – Tass Jun 23 '15 at 13:25
@victor-deryagin .. I am new to these, so a very basic question ,why is that 1 used in regexp, – Hridya Jul 21 '15 at 08:58

score 4 · Answer 2 · answered Jan 23 '15 at 15:35

4

Using the same regex given by Victor, you can also do

var.split(/container_start(.*?)container_end/)[1]

answered Jan 23 '15 at 15:35

Dennis

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score 2 · Answer 3 · answered Feb 01 '16 at 03:33

Just to provide a non-regex answer, you can also use two .splits with selection of array entries.

=> @var = "Hi, I want to extract container_start ONLY THIS DYNAMIC CONTENT container_end from the message contained between the container_start and container_end "
=> @var.split("container_start ")[1].split(" container_end")[0]
=> "ONLY THIS DYNAMIC CONTENT"

.split splits the string at the text in the quotes. The [1] selects the portion AFTER that text. For the second cut, you want the portion BEFORE the "container_end" so you select [0].

You need to leave the spaces in the two .split substrings to remove leading and trailing spaces. Alternately, use .lstrip and .rstrip.

If there were more "container_start" and "container_end" strings you would need to adjust the array selectors to pick the correct portion of @var between those two substrings.

score 0 · Answer 4 · answered Feb 22 '20 at 17:22

I just wanted to add something important that I got from here

@var = "Hi, I want to extract container_start \n\nONLY \nTHIS\n DYNAMIC\n CONTENT\n\n container_end from the message contained between the container_start and container_end "
@var[/container_start(.*?)container_end/m, 1]

Took the except:

/./ - Any character except a newline.
/./m - Any character (the m modifier enables multiline mode)

Fetching the substring contained between two specific words

4 Answers4