Codebox Software

RegEx.DLL provides some much needed regular-expression handling for VB programmers. The 'clsRegEx' class implements all the common UNIX wildcard characters allowing sophisticated string comparisons and search-and-replace operations to be performed.

• The '*' character represents zero or more occurrences of the previous character in the expression:
  ab*c matches ac, abc, abbc, abbbbbbbc ...
• The '+' character represents one or more occurrences of the previous character in the expression:
  ab+c matches abc, abbc, abbbbbbbc but not ac
• Numbers within curly brackets represent a specific number of occurrences of the previous character:
  a{3} matches aaa a{3,5} matches aaa, aaaa and aaaaa
• The '?' character represents zero or one occurrences of the previous character:
  a?c matches ac and aac
• The '.' character represents any single character:
  a.c matches abc, aXc but not ac or abbc

Round brackets can be used to apply multipliers, such as '*' or '+', to groups of characters:

• (abc)* matches an empty string, abc, abcabc, abcabcabc ...
• (abc)+ matches abc, abcabc, abcabcabc ...
• (a.c)* matches an empty string, abc, abcaXc, aXcaYcaZc ...

Square brackets can be used to specify possible values for a single character. A hyphen can be used in this context to represent a range of characters. If the first character within the brackets is a '^' then the range is exclusive rather than inclusive (ie. the expression matches any single character not shown):

• a[bB]c matches abc and aBc
• a[0-9]c matches a0c, a1c, a2c ... a9c
• a[^0-9]c matches abc and aXc but not a0c ... a9c

A '\' symbol negates the special meaning of the following character. Only valid if it precedes one of *+?\{([])}.

• a\*c matches a*c
• a[\[\]]c matches a]c and a[c
• a\\c matches a\c
• >ab\c is not a valid expression

The download includes VB code samples demonstrating how to use the library.