XQuery

Representing Any Character

The period (.) has special significance in regular expressions; it matches any character except the line feed character (#xA). The period character represents only one matching character, but a quantifier (such as *) can be applied to it to represent multiple characters. Table 18-6 shows some examples of the wildcard escape character in use.

Table 18-6. The wildcard escape character

Regular expression	Strings that match	Strings that do not match
[a]
f.o	fao, fbo, f2o	fo, fbbo
f..o	faao, fbco, f12o	fo, fao
f.*o	fo, fao, fbcde23o	f [a]
f\.o	f.o	fao
[a] Assume a line feed character between f and o. This string does not match unless you are in dot-all mode.

It is important to note that the period loses its wildcard power when placed in a character class expression (within square brackets).

Some XQuery functions (namely matches, replace, and tokenize) allow you to indicate that the processor should operate in dot-all mode. This is specified using the letter s in the $flags argument. In dot-all mode, the period matches any character whatsoever, including the line feed character (#xA). See "Using Flags," later in this chapter, for more information.