REGEX: Matching a String to a Regular Expression

How to:

The REGEX function matches a string to a regular expression and returns true (1) if it matches and false (0) if it does not match.

A regular expression is a sequence of special characters and literal characters that you can combine to form a search pattern.

Many references for regular expressions exist on the web.

Syntax: How to Match a String to a Regular Expression 

REGEX(string, regular_expression)

where:

string

Alphanumeric

Is the character string to match.

regular_expression

Alphanumeric

Is a regular expression, enclosed in single quotation marks, constructed using literals and meta-characters. The following meta-characters are supported

  • . represents any single character
  • * represents zero or more occurrences
  • + represents one or more occurrences
  • ? represents zero or one occurrence
  • ^ represents beginning of line
  • $ represents end of line
  • [] represents any one character in the set listed within the brackets
  • [^] represents any one character not in the set listed within the brackets
  • | represents the Or operator
  • \ is the Escape Special Character
  • () contains a character sequence

For example, the regular expression '^Ste(v|ph)en$' matches values starting with Ste followed by either ph or v, and ending with en.

Note: The output value is numeric.

Example: Matching a String Against a Regular Expression

The following request matches the FIRSTNAME field against the regular expression 'PATRIC[(I?)K]', which matches PATRICIA or PATRICK: 

DEFINE FILE VIDEOTRK   
PNAME/I5=REGEX(FIRSTNAME,'PATRIC[(I?)K]');                   
END                                                                   
TABLE FILE VIDEOTRK  
PRINT FIRSTNAME PNAME
BY LASTNAME
WHERE LASTNAME GE 'M'
ON TABLE SET PAGE NOLEAD
ON TABLE SET STYLE *
GRID=OFF,$
ENDSTYLE
END

The output is shown in the following image.

The following version of the request runs on z/OS. The variable &REG1 contains the regular expression string with the circumflex character (^) inserted as CHAR(95), the left bracket character ([) inserted as CHAR(173), and the right bracket character (]) inserted as CHAR(189). The other meta-characters are interpreted correctly. 

-SET &REG1 = CHAR(95) || 'PATRIC' || CHAR(173) || 
- '(I?)K' || CHAR(189);                                 
DEFINE FILE VIDEOTRK                                    
PNAME/I5 = REGEX(FIRSTNAME,'&REG1') ;                   
END                                         
TABLE FILE VIDEOTRK                                 
PRINT FIRSTNAME PNAME    
BY LASTNAME                  
WHERE LASTNAME GE 'M' 
ON TABLE SET PAGE NOLEAD
 END

The output follows.

  LASTNAME         FIRSTNAME   PNAME 
  --------         ---------   ----- 
  MCMAHON          JOHN            0 
  MONROE           CATHERINE       0 
                   PATRICK         1 
  NON-MEMBER                       0 
  O'BRIEN          DONALD          0 
  PARKER           GLENDA          0 
                   RICHARD         0 
  RATHER           MICHAEL         0 
  RIESLER          LESLIE          0 
  SPIVEY           TOM             0 
  STANDLER         MICHAEL         0 
  STEWART          MAUDE           0 
  WHITE            PATRICIA        1 
  WILLIAMS         KENNETH         0 
  WILSON           KELLY           0 
  WU               MARTHA          0