PRXMATCH Function

Searches for a pattern match and returns the position at which the pattern is found.

Category:

Character String Matching

Syntax

PRXMATCH (regular-expression-id | perl-regular-expression, source)

Required Arguments

regular-expression-id

specifies a numeric variable with a value that is a pattern identifier that is returned from the PRXPARSE function.

Restriction

If you use this argument, you must also use the PRXPARSE function.

perl-regular-expression

specifies a character constant, variable, or expression with a value that is a Perl regular expression.

source

specifies a character constant, variable, or expression that you want to search.

Details

The Basics

If you use regular-expression-id, then the PRXMATCH function searches source with the regular-expression-id that is returned by PRXPARSE, and returns the position at which the string begins. If there is no match, PRXMATCH returns a zero.

If you use perl-regular-expression, PRXMATCH searches source with the perl-regular-expression, and you do not need to call PRXPARSE.

You can use PRXMATCH with a Perl regular expression in a WHERE clause and in PROC SQL. For more information about pattern matching, see Pattern Matching Using Perl Regular Expressions (PRX) .

Compiling a Perl Regular Expression

If perl-regular-expression is a constant or if it uses the /o option, then the Perl regular expression is compiled once and each use of PRXMATCH reuses the compiled expression. If perl-regular-expression is not a constant and if it does not use the /o option, then the Perl regular expression is recompiled for each call to PRXMATCH.

Note: The compile-once behavior occurs when you use PRXMATCH in a DATA step, in a WHERE clause, or in PROC SQL. For all other uses, the perl-regular-expression is recompiled for each call to PRXMATCH.

Comparisons

The Perl regular expression (PRX) functions and CALL routines work together to manipulate strings that match patterns. To see a list and short description of these functions and CALL routines, see the Character String Matching category in SAS Functions and CALL Routines by Category.

Examples

Example 1: Finding the Position of a Substring by Using PRXPARSE

The following example searches a string for a substring, and returns its position in the string.

/* For 9.0: the following example makes a call to PRXPARSE. */
  /* For 9.1, no call is required. */

  data _null_;
      /* Use PRXPARSE to compile the Perl regular expression.    */
   patternID = prxparse('/world/');
      /* Use PRXMATCH to find the position of the pattern match. */
   position=prxmatch(patternID, 'Hello world!');
   put position=;
run;

SAS writes the following line to the log:

   position=7

Example 2: Finding the Position of a Substring by Using a Perl Regular Expression

The following example uses a Perl regular expression to search a string (Hello world) for a substring (world) and to return the position of the substring in the string.

data _null_;
      /* Use PRXMATCH to find the position of the pattern match. */
   position=prxmatch('/world/', 'Hello world!');
   put position=;
run;

SAS writes the following line to the log:

   position=7

Example 3: Finding the Position of a Substring in a String: A Complex Example

The following example uses several Perl regular expression functions and a CALL routine to find the position of a substring in a string.

data _null_;
   if _N_ = 1 then
   do;
      retain PerlExpression;
      pattern = "/(\d+):(\d\d)(?:\.(\d+))?/";
      PerlExpression = prxparse(pattern);
   end;
  
   array match[3] $ 8;
   input minsec $80.;
   position = prxmatch(PerlExpression, minsec);
   if position ^= 0 then
   do;
      do i = 1 to prxparen(PerlExpression);
         call prxposn(PerlExpression, i, start, length);
         if start ^= 0 then
            match[i] = substr(minsec, start, length);
      end;
      put match[1] "minutes, " match[2] "seconds" @;
      if ^missing(match[3]) then
         put ", " match[3] "milliseconds";
   end;
   datalines;
14:56.456
45:32
;
run;

The following lines are written to the SAS log:

   14 minutes, 56 seconds, 456 milliseconds
   45 minutes, 32 seconds

Example 4: Extracting a ZIP Code by Using the DATA Step

The following example uses a DATA step to search each observation in a data set for a nine-digit ZIP code, and writes those observations to the data set ZipPlus4.

data ZipCodes;
   input name: $16. zip:$10.;
   datalines;
Johnathan 32523-2343
Seth 85030
Kim 39204
Samuel 93849-3843
;
   /* Extract ZIP+4 ZIP codes with the DATA step. */
data ZipPlus4;
   set ZipCodes;
   where prxmatch('/\d{5}-\d{4}/', zip);
run;
proc print data=ZipPlus4;
run;

ZIP Code Output from the DATA Step

Example 5: Extracting a ZIP Code by Using PROC SQL

The following example searches each observation in a data set for a nine-digit ZIP code, and writes those observations to the data set ZipPlus4.

data ZipCodes;
   input name: $16. zip:$10.;
   datalines;
Johnathan 32523-2343
Seth 85030
Kim 39204
Samuel 93849-3843
;
   /* Extract ZIP+4 ZIP codes with PROC SQL. */
proc sql;
   create table ZipPlus4 as
   select * from ZipCodes 
   where prxmatch('/\d{5}-\d{4}/', zip);
run;
proc print data=ZipPlus4;
run;

ZIP Code Output from PROC SQL