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.
- greedy and non-greedy
- Support the following macros
- []
- a-z
- A-Z
- 0-9
- Individual characters and numbers
- ^
- $
- .
- ?
- +
- *
- \d
- \w
- \s
- escape characters
- []
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)
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.
$ make
$ ./output