Pattern Matching Features
This discussion of pattern matching is from Microsoft’s Visual Basic Help File (VB5.HLP).
Built-in pattern matching provides a versatile tool for making string
comparisons. The following table shows the wildcard characters you can use with the
Like operator and the number of digits or strings they match.
Character(s) in pattern Matches in expression
? Any single character
* Zero or more characters
# Any single digit (09)
[charlist] Any single character in charlist
[!charlist] Any single character not in charlist
A group of one or more characters (charlist) enclosed in brackets ([ ]) can be
used to match any single character in expression and can include almost any
characters in the ANSI character set, including digits. In fact, the special
characters opening bracket ([ ), question mark (?), number sign (#), and asterisk
(*) can be used to match themselves directly only if enclosed in brackets. The
closing bracket ( ]) can't be used within a group to match itself, but it can
be used outside a group as an individual character.
In addition to a simple list of characters enclosed in brackets, charlist can
specify a range of characters by using a hyphen (-) to separate the upper and
lower bounds of the range. For example, using [A-Z] in pattern results in a
match if the corresponding character position in expression contains any of the
uppercase letters in the range A through Z. Multiple ranges can be included within
the brackets without any delimiting. For example, [a-zA-Z0-9] matches any
alphanumeric character.
Other important rules for pattern matching include the following:
· An exclamation mark (!) at the beginning of charlist means that a match is
made if any character except those in charlist are found in expression. When used
outside brackets, the exclamation mark matches itself.
· The hyphen (-) can be used either at the beginning (after an exclamation mark
if one is used) or at the end of charlist to match itself. In any other
location, the hyphen is used to identify a range of ANSI characters.
· When a range of characters is specified, they must appear in ascending sort
order (A-Z or 0-100). [A-Z] is a valid pattern, but [Z-A] isn't.
· The character sequence [ ] is ignored; it's considered to be a zero-length
string ("").