· regex

Regular-Expression (RegEx)

Meta-characters:

Basic RegExs

1. Alphanumeric (a-z, A-Z, 0-9, _) - literal characters

Meta-characters

1. “*” - matches zero or more times the preceding token

i.e. [Ll]inux[0-9]* - matches ‘linux’, ‘Linux’, ‘Linux1’, ‘Linux[n]’

2. “?” - marks preceding token as optional - zero OR one time

i.e. favou?r - matches ‘favor’, ‘favour’

3. “+” - matches the preceding token one or more times

i.e. Linu+x - matches ‘Linux’, ‘Linuux’

4. “[ ]” - brackets -are used to define character classes. The match ONE charter and NOT a group of characters

i.e Linux[Xx0-9] - matches ‘Linuxx’, ‘LinuxX’, ‘Linux0-9’

5. “( )” - parentheses - are used to group characters and to constrain alternation

NOTE: Parentheses permit the grouping of several characters (words) for matches

i.e (Linux)+

6. “^” - anchors text at the beginning, including at the beginning of a line

7. “$” - anchors text at the end, including at the end of a line

8. “|” - matches alternate character

9. “.” - matches any characters except line breaks

10. “\” - used to escape the following character

11. “{max}” - quantifier for preceding token

12. “{min,max}” - {3,5} - matches at least 3 times and up to 5 times

i.e Linu[x]{2,3} - matches ‘Linuxx’, ‘Linuxxx’

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