Searching with the Asterisk Character

The asterisk character is used to match a sequence of zero or more characters in a character sequence. Returning to our constants example:

#define threshold_low  2400

#define threshold_high 4800

#define threshold_mid  3600

In our previous case we used the + character to match a sequence of one or more characters. Our search string was:

threshold_[A-Za-z]+

Alternatively, we could have used the asterisk character * to match our character sequence zero or more times. Our new expression becomes:

threshold_[A-Za-z]*

This will now match the following strings:

#define threshold_low  2400

#define threshold_high 4800

#define threshold_mid  3600

It will stop at the first character that is not in the given set. However, if we had an expression:

#define threshold_

it would match this expression as well and we would get the following:

#define threshold_low  2400

#define threshold_high 4800

#define threshold_mid  3600

#define threshold_

This is because the * character matches 0 or more occurrences of the character specified in our group. In the last example, threshold_ has 0 or more characters in our set [A-Za-z] so it matches as well.

In the next example we'll look at matching a sequence of characters starting at the beginning of the line.