Humdrum lab 7

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Regular Expressions

Basic Regular Expressions

"Basic" regular expressions are the initial implementation of grep, that came with unix in 1973. Here are the "metacharacters" in the basic implementation of regular expressions:

Basic-regular-expressions.png

Dot metacharacter

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.

Basic-regular-expression-dot.png


Star metacharacter

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.

Basic-regular-expression-star.png