| Regular expression is an expression by which searching of codes is made simpler it is defined by American mathematician Stephen Kleene |
Regular expression has this below 4 parts in it |
| Literal | Character we use in search |
| Metacharacter | Special character that we use in regular expression eg: $ ^ |
| Escape string | A way of indicating the user of metacharacter |
| Search expression | Search string that we use to search target string |
Symbols in meta characters |
| Brackets [] | Matching of single characters or multiple characters in the stiring |
| - | Range Operators ex : a-z (lower case from a to z) |
| ^ | Expect or not operator ex : [^aA] any character not a and A |
| $ | Will look only at the end of string |
| . | Will replace any character on . ex .in matches windows, linux |
| ? | Matches preceding characters only once. |
| * | Matches preceding characters multiple times |
| | | also called alternation matches left or right side characters ex : gr(a|e)y matches grey and gray |
Examples: |
| [^0-9] | Any character other than a number |
| [0-9]] | Any number followed by a "]" |
| [0-9\-a\]] | Any number, or a "-", a "a", or a "]" |
| ^AA* | Any line if it starts with one "A" |
No comments:
Post a Comment