Some special characters are used to specify how many times a character will be repeated in the text. These special characters are:
- the plus +
- a plus sign after a character indicates that it can occur at least one or more times
- the asterisk *
- Asterisk after a character means that it may either not match at all or can match many times.
- the question mark ?
- A question mark after a character indicates that a character is optional
br ber beer /be*r/g br ber beer
br ber beer /be+r/g ber
dp dep deep /de*p/g dp dep deep
color, colour /colou?r/g color colour
a, an /an?/g a an
- To express a certain number of occurrences of a character, at the end we write curly braces {n} along with how many times we want it to occur.
- To express the occurrence of a character in a certain number range, we write curly braces {x,y} with the interval we want to go to the end.
- To express at least a certain number of occurrences of a character, we write the end of the character at least how many times we want it to occur, with a comma , at the end, and inside curly braces {n, }.
ber beer beeer beeeer /be{2}r/g beer
ber beer beeer beeeer /be{3}r/g beeer
ber beer beeer beeeer /be{2,}r/g beer beeer beeeer
ber beer beeer beeeer /be{1,4}r/g ber beer beeer beeeer
ber beer beeer beeeer /be{2,3}r/g beer beeer
ber beer beeer beeeer /be{3,}r/g beeer beeeer
Release 10/9/2021 /[0-9]{4}/g 2021
Release 10/9/2021 /[0-9]{2,}/g 10 2021
Release 10/9/2021 /[0-9]{1,4}/g 10 9 2021