programming-for-dummies

170
Finding Strings with Regular Expressions
This finds buz and buzzzz but not bu because the (+) wildcard needs to find
at least a z character.
Pattern matching with ranges
Wildcards can match zero or more characters, but sometimes you may want
to know whether a particular character falls within a range or characters. To
do this, you can use ranges. For example, if you want to know whether a
character is any letter, you could use the pattern [a-z] as follows:
bu[a-z]
This finds strings, such as but, bug, or bus, but not bu (not a three-character
string). Of course, you don’t need to search for letters from a to z. You can
just as well search for the following:
bu[d-s]
This regular expression finds bud and bus but not but (because the t lies outside
the range of letters from d to s).
You can also use ranges to check whether a character falls within a numeric
range, such as
21[0-9]
This finds the strings 212 and 210. If you only wanted to find strings with
numbers between 4 and 7, you’d use this regular expression:
21[4-7]
This finds the strings 215 but not the strings 210 or 218 because both 0 and 8
lie outside the defined range of 4–7. Table 3-6 shows examples of different
regular expressions and the strings that they find.
This section shows a handful of regular expression symbols you can use to
search for string patterns. A lot more regular expressions can perform all
sorts of weird and wonderful pattern searching, so you can always find out
more about these other options by browsing www.regular-expressions.
info.
By stringing multiple regular expression wildcards together, you can search
for a variety of different string patterns, as shown in Table 3-6.