Introduction to Regular Expressions in SAS

120 Pages·2014·3.171 MB·English

by  Matthew Windham

Introduction to
Regular Expressions
in SAS®
K. Matthew Windham
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The correct bibliographic citation for this manual is as follows: Windham, K. Matthew. 2014. Introduction to
Regular Expressions in SAS®. Cary, NC: SAS Institute Inc.
Introduction to Regular Expressions in SAS®
Copyright © 2014, SAS Institute Inc., Cary, NC, USA
ISBN 978-1-61290-904-2 (Hardcopy)
ISBN 978-1-62959-498-9 (EPUB)
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Contents

About This Book ........................................................................................ vii
About The Author ...................................................................................... xi
Acknowledgments .................................................................................... xiii
Chapter 1: Introduction .............................................................................. 1
1.1 Purpose of This Book .............................................................................................................. 1
1.2 Layout of This Book ................................................................................................................. 1
1.3 Defining Regular Expressions ................................................................................................. 2
1.4 Motivational Examples ............................................................................................................ 3
1.4.1 Extract, Transform, and Load (ETL) .............................................................................. 3
1.4.2 Data Manipulation .......................................................................................................... 4
1.4.3 Data Enrichment ............................................................................................................. 5
Chapter 2: Getting Started with Regular Expressions ................................. 9
2.1 Introduction ............................................................................................................................ 10
2.1.1 RegEx Test Code .......................................................................................................... 11
2.2 Special Characters ................................................................................................................. 13
2.3 Basic Metacharacters ............................................................................................................ 15
2.3.1 Wildcard ......................................................................................................................... 15
2.3.2 Word ............................................................................................................................... 15
2.3.3 Non-word ....................................................................................................................... 16
2.3.4 Tab.................................................................................................................................. 16
2.3.5 Whitespace .................................................................................................................... 17
2.3.6 Non-whitespace ............................................................................................................ 17
2.3.7 Digit ................................................................................................................................ 17
2.3.8 Non-digit ........................................................................................................................ 18
2.3.9 Newline .......................................................................................................................... 18
2.3.10 Bell ............................................................................................................................... 19
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2.3.11 Control Character ....................................................................................................... 20
2.3.12 Octal ............................................................................................................................. 20
2.3.13 Hexadecimal ................................................................................................................ 21
2.4 Character Classes .................................................................................................................. 21
2.4.1 List .................................................................................................................................. 21
2.4.2 Not List........................................................................................................................... 22
2.4.3 Range ............................................................................................................................. 22
2.5 Modifiers ................................................................................................................................. 23
2.5.1 Case Modifiers .............................................................................................................. 23
2.5.2 Repetition Modifiers ..................................................................................................... 25
2.6 Options .................................................................................................................................... 32
2.6.1 Ignore Case ................................................................................................................... 32
2.6.2 Single Line ..................................................................................................................... 32
2.6.3 Multiline ......................................................................................................................... 33
2.6.4 Compile Once ................................................................................................................ 33
2.6.5 Substitution Operator ................................................................................................... 34
2.7 Zero-width Metacharacters .................................................................................................. 34
2.7.1 Start of Line ................................................................................................................... 35
2.7.2 End of Line ..................................................................................................................... 35
2.7.3 Word Boundary ............................................................................................................. 35
2.7.4 Non-word Boundary ..................................................................................................... 36
2.7.5 String Start .................................................................................................................... 36
2.8 Summary ................................................................................................................................. 37
Chapter 3: Using Regular Expressions in SAS ........................................... 39
3.1 Introduction ............................................................................................................................ 39
3.1.1 Capture Buffer............................................................................................................... 39
3.2 Built-in SAS Functions ........................................................................................................... 40
3.2.1 PRXPARSE .................................................................................................................... 40
3.2.2 PRXMATCH ................................................................................................................... 42
3.2.3 PRXCHANGE ................................................................................................................. 43
3.2.4 PRXPOSN ...................................................................................................................... 46
3.2.5 PRXPAREN .................................................................................................................... 47
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3.3 Built-in SAS Call Routines ..................................................................................................... 49
3.3.1 CALL PRXCHANGE ...................................................................................................... 50
3.3.2 CALL PRXPOSN ............................................................................................................ 54
3.3.3 CALL PRXSUBSTR ....................................................................................................... 56
3.3.4 CALL PRXNEXT ............................................................................................................ 57
3.3.5 CALL PRXDEBUG ......................................................................................................... 59
3.3.6 CALL PRXFREE ............................................................................................................. 62
3.4 Summary ................................................................................................................................. 63
Chapter 4: Applications of Regular Expressions in SAS ............................ 65
4.1 Introduction ............................................................................................................................ 65
4.1.1 Random PII Generator ................................................................................................. 66
4.2 Data Cleansing and Standardization .................................................................................... 72
4.3 Information Extraction ........................................................................................................... 77
4.4 Search and Replacement ...................................................................................................... 80
4.5 Summary ................................................................................................................................. 83
4.5.1 Start Small ..................................................................................................................... 83
4.5.2 Think Big ........................................................................................................................ 83
Appendix A: Perl Version Notes ................................................................ 85
Appendix B: ASCII Code Lookup Tables .................................................... 87
Non-Printing Characters ............................................................................................................. 87
Printing Characters ...................................................................................................................... 89
Appendix C: POSIX Metacharacters .......................................................... 97
Index ...................................................................................................... 101
vi
About This Book
Purpose
This book is intended for a wide audience of SAS users, from novice programmer to the very
advanced. As not much has previously been published on this topic, many different skill levels can
benefit from the content herein. However, the book has been written to ensure that novice
programmers can immediately implement every element discussed.
Is This Book for You?
Of course, it is! Do you wish you could process unstructured data sources? Would you like to more
effectively process semi-structured data sources? Do you want to one day leverage advanced text
mining concepts within your Base SAS code? Of course, you do! This book lays the foundation for all
of this and more, making it the ideal text for anyone wanting to enhance their programming prowess.
Prerequisites
Readers should be comfortable using and applying the SAS DATA step, basic PROCs (e.g., PROC
PRINT), DO loops, and conditional processing concepts. Readers should be familiar with SAS arrays
and the RETAIN statement.
Scope of This Book
This book covers all PRX functions and call routines.
This book does NOT cover advanced concepts requiring MACRO programming, PROC SQL, or
system automation.
About the Examples
Software Used to Develop the Book's Content
Base SAS (Microsoft Windows)
viii

Example Code and Data
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Output and Graphics Used in This Book
All output used in this book was generated via the SAS log and PROC PRINT.
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ix

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