Create README.md

Author: vinayakphegde

README.md

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+# regex-engine
+## Introduction
+A regular expression (shortened as regex or regexp) is a sequence of characters that specifies a search pattern. Regular expressions are extremely useful in 
+extracting information from any text by searching for one or more matches of a specific search pattern 
+(i.e. a specific sequence of ASCII or unicode characters).Usually such patterns are used by string-searching algorithms for
+"find" or "find and replace" operations on strings, or for input validation.
+
+It is a technique developed in theoretical computer science and formal language theory.
+Fields of application range from validation to parsing/replacing strings, passing through translating data to other formats and web scraping.
+
+## Operations supported
+* greedy and non-greedy
+* Support the following macros
+  * []
+	*	a-z
+	*	A-Z
+	*	0-9
+	*	Individual characters and numbers
+  * ^
+  * $
+  * .
+  * ?
+  * \+
+  * \*
+  * \d
+  * \w
+  * \s
+  * escape characters
+
+## Function/Interface supported
+match is the only function supported for the client as an interface. all other functions are not available to the client, they are implementation functions
+(internal static functions)
+### match
+```c
+node_t *match(char *pat, char *text);
+```
+it returns starting and ending position of the string if the substring of text matches with the pattern else returns null.
+
+## Usage
+```
+$ make
+$ ./output 
+```