Functions and CALL Routines

Pattern Matching Using Perl Regular Expressions (PRX)

Pattern matching enables you to search for and extract multiple matching patterns from a character string in one step. Pattern matching also enables you to make several substitutions in a string in one step. You do this by using the PRX functions and CALL routines in the DATA step.

For example, you can search for multiple occurrences of a string and replace those strings with another string. You can search for a string in your source file and return the position of the match. You can find words in your file that are doubled.

Definition of Perl Regular Expression (PRX) Functions and CALL Routines

Perl regular expression (PRX) functions and CALL routines refers to a group of functions and CALL routines that use a modified version of Perl as a pattern-matching language to parse character strings. You can do the following:

search for a pattern of characters within a string
extract a substring from a string
search and replace text with other text
parse large amounts of text, such as Web logs or other text data

Perl regular expressions comprise the character string matching category for functions and CALL routines. For a short description of these functions and CALL routines, see the Functions and CALL Routines by Category.

Benefits of Using Perl Regular Expressions in the DATA Step

Using Perl regular expressions in the DATA step enhances search-and-replace options in text. You can use Perl regular expressions to perform the following tasks:

validate data
replace text
extract a substring from a string

You can write SAS programs that do not use regular expressions to produce the same results as you do when you use Perl regular expressions. However, the code without the regular expressions requires more function calls to handle character positions in a string and to manipulate parts of the string.

Perl regular expressions combine most, if not all, of these steps into one expression. The resulting code is less prone to error, easier to maintain, and clearer to read.

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