Humdrum lab 7
Basic Regular Expressions
The dot, or period, character is used to indicate any single character. In the following example, the regular expressin "c.t" will match to any three characters which start with "c", end with "t", and have any single character between these two characters.
The star, or asterisk, character is used to indicate the the previous character (or parentheses group) will be matched if it occurs 0 or more times in the search string.
In the following example, the regular expression "c*t" will match to strings that contain zero or more "c" characters followed by the letter "t":
Note that "*" must be preceded by a character. If the "*" comes at the start of a line, that is an error because there is nothing to the left of the star for it to operate on.