From 4dac3f3fc948dcc1aa661bd4e61c8034bd1bf1ad Mon Sep 17 00:00:00 2001 From: Aakash Panchal <51417248+Aakash-Panchal27@users.noreply.github.com> Date: Sun, 8 Mar 2020 13:02:25 +0530 Subject: [PATCH] Create Practial_applications.html --- .../RegEx/Practial_applications.html | 129 ++++++++++++++++++ 1 file changed, 129 insertions(+) create mode 100644 Akash Articles/RegEx/Practial_applications.html diff --git a/Akash Articles/RegEx/Practial_applications.html b/Akash Articles/RegEx/Practial_applications.html new file mode 100644 index 0000000..c3fdf5e --- /dev/null +++ b/Akash Articles/RegEx/Practial_applications.html @@ -0,0 +1,129 @@ + + + + + + + + + + + + +

Practical Applications of RegEx

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  1. Syntax highlighting systems
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  2. Data scraping and wrangling
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  3. In find and replace facility of text editors
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Let's look at some classical examples of RegEx.

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Number Ranges

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Can you find a regex matching all integers from 0 to 255?

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First, Let's look at how can we match all integers from 0 to 59:

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As you can see, we have used ? quantifier to make the first digit(0-5) optional. Now, can you solve it for 0-255?

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Hint : Use OR operator.

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We can divide the range 0-255 into three ranges: 0-199, 200-249 & 250-255. Now, creating an expression, for each of them independently, is easy.

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|   Range| RegEx |
+		|   :--:    |   :--:    |
+		| 0-199 | `[01][0-9][0-9]` |
+		| 200-249| `2[0-4][0-9]`|
+		| 250-255| `25[0-5]`|
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Now, by using OR operator, we can match the whole 0-255 range.

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As you can see, the above regex is not going to match 0, but 000. So, how can you modify the regex which matches 0 as well, rather than matching 001 only?

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We have just used ? quantifier.

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Validate an IP address

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IP address consists of digits from 0-255 and 3 points(.). Valid IP address format is (0-255).(0-255).(0-255).(0-255).

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For example, 10.10.11.4, 255.255.255.255, 234.9.64.43, 1.2.3.4 are Valid IP addresses.

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Can you find a regex to match an IP-address?

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We have already seen, how to match number ranges and to match a point, we use escaped-dot(\.). But in IP address, we don't allow leading zeroes in numbers like 001.

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So, We have to divide the range in four sub-ranges: 0-99, 100-199, 200-249, 250-255. And finally we use OR-operator.

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So, Regex to match IP Address is as below: + enter image description here

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Note: The whole expression is contiguous, for the shake of easy understanding it is shown the way it is.

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