Table of Contents for
sed & awk, 2nd Edition

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition sed & awk, 2nd Edition by Arnold Robbins Published by O'Reilly Media, Inc., 1997
  1. sed & awk, 2nd Edition
  2. Cover
  3. sed & awk, 2nd Edition
  4. A Note Regarding Supplemental Files
  5. Dedication
  6. Preface
  7. Scope of This Handbook
  8. Availability of sed and awk
  9. Obtaining Example Source Code
  10. Conventions Used in This Handbook
  11. About the Second Edition
  12. Acknowledgments from the First Edition
  13. Comments and Questions
  14. 1. Power Tools for Editing
  15. 1.1. May You Solve Interesting Problems
  16. 1.2. A Stream Editor
  17. 1.3. A Pattern-Matching Programming Language
  18. 1.4. Four Hurdles to Mastering sed and awk
  19. 2. Understanding Basic Operations
  20. 2.1. Awk, by Sed and Grep, out of Ed
  21. 2.2. Command-Line Syntax
  22. 2.3. Using sed
  23. 2.4. Using awk
  24. 2.5. Using sed and awk Together
  25. 3. Understanding Regular Expression Syntax
  26. 3.1. That’s an Expression
  27. 3.2. A Line-Up of Characters
  28. 3.3. I Never Metacharacter I Didn’t Like
  29. 4. Writing sed Scripts
  30. 4.1. Applying Commands in a Script
  31. 4.2. A Global Perspective on Addressing
  32. 4.3. Testing and Saving Output
  33. 4.4. Four Types of sed Scripts
  34. 4.5. Getting to the PromiSed Land
  35. 5. Basic sed Commands
  36. 5.1. About the Syntax of sed Commands
  37. 5.2. Comment
  38. 5.3. Substitution
  39. 5.4. Delete
  40. 5.5. Append, Insert, and Change
  41. 5.6. List
  42. 5.7. Transform
  43. 5.8. Print
  44. 5.9. Print Line Number
  45. 5.10. Next
  46. 5.11. Reading and Writing Files
  47. 5.12. Quit
  48. 6. Advanced sed Commands
  49. 6.1. Multiline Pattern Space
  50. 6.2. A Case for Study
  51. 6.3. Hold That Line
  52. 6.4. Advanced Flow Control Commands
  53. 6.5. To Join a Phrase
  54. 7. Writing Scripts for awk
  55. 7.1. Playing the Game
  56. 7.2. Hello, World
  57. 7.3. Awk’s Programming Model
  58. 7.4. Pattern Matching
  59. 7.5. Records and Fields
  60. 7.6. Expressions
  61. 7.7. System Variables
  62. 7.8. Relational and Boolean Operators
  63. 7.9. Formatted Printing
  64. 7.10. Passing Parameters Into a Script
  65. 7.11. Information Retrieval
  66. 8. Conditionals, Loops, and Arrays
  67. 8.1. Conditional Statements
  68. 8.2. Looping
  69. 8.3. Other Statements That Affect Flow Control
  70. 8.4. Arrays
  71. 8.5. An Acronym Processor
  72. 8.6. System Variables That Are Arrays
  73. 9. Functions
  74. 9.1. Arithmetic Functions
  75. 9.2. String Functions
  76. 9.3. Writing Your Own Functions
  77. 10. The Bottom Drawer
  78. 10.1. The getline Function
  79. 10.2. The close( ) Function
  80. 10.3. The system( ) Function
  81. 10.4. A Menu-Based Command Generator
  82. 10.5. Directing Output to Files and Pipes
  83. 10.6. Generating Columnar Reports
  84. 10.7. Debugging
  85. 10.8. Limitations
  86. 10.9. Invoking awk Using the #! Syntax
  87. 11. A Flock of awks
  88. 11.1. Original awk
  89. 11.2. Freely Available awks
  90. 11.3. Commercial awks
  91. 11.4. Epilogue
  92. 12. Full-Featured Applications
  93. 12.1. An Interactive Spelling Checker
  94. 12.2. Generating a Formatted Index
  95. 12.3. Spare Details of the masterindex Program
  96. 13. A Miscellany of Scripts
  97. 13.1. uutot.awk—Report UUCP Statistics
  98. 13.2. phonebill—Track Phone Usage
  99. 13.3. combine—Extract Multipart uuencoded Binaries
  100. 13.4. mailavg—Check Size of Mailboxes
  101. 13.5. adj—Adjust Lines for Text Files
  102. 13.6. readsource—Format Program Source Files for troff
  103. 13.7. gent—Get a termcap Entry
  104. 13.8. plpr—lpr Preprocessor
  105. 13.9. transpose—Perform a Matrix Transposition
  106. 13.10. m1—Simple Macro Processor
  107. A. Quick Reference for sed
  108. A.1. Command-Line Syntax
  109. A.2. Syntax of sed Commands
  110. A.3. Command Summary for sed
  111. B. Quick Reference for awk
  112. B.1. Command-Line Syntax
  113. B.2. Language Summary for awk
  114. B.3. Command Summary for awk
  115. C. Supplement for Chapter 12
  116. C.1. Full Listing of spellcheck.awk
  117. C.2. Listing of masterindex Shell Script
  118. C.3. Documentation for masterindex
  119. masterindex
  120. C.3.1. Background Details
  121. C.3.2. Coding Index Entries
  122. C.3.3. Output Format
  123. C.3.4. Compiling a Master Index
  124. Index
  125. About the Authors
  126. Colophon
  127. Copyright

Command-Line Syntax

The syntax for invoking awk has two basic forms: 

awk [-v var=value] [-Fre] [--] 'pattern { action }' var=value datafile(s)
awk [-v var=value] [-Fre] -f scriptfile [--] var=value datafile(s)

An awk command line consists of the command, the script and the input filename. Input is read from the file specified on the command line. If there is no input file or “-” is specified, then standard input is read. The -F option sets the field separator (FS) to re.

The -v option sets the variable var to value before the script is executed. This happens even before the BEGIN procedure is run. (See the discussion below on command-line parameters.)

Following POSIX argument parsing conventions, the "--" option marks the end of command-line options. Using this option, for instance, you could specify a datafile that begins with “-”, which would otherwise be confused with a command-line option.

You can specify a script consisting of pattern and action on the command line, surrounded by single quotes. Alternatively, you can place the script in a separate file and specify the name of the scriptfile on the command line with the -f option.

Parameters can be passed into awk by specifying them on the command line after the script. This includes setting system variables such as FS, OFS, and RS. The value can be a literal, a shell variable ($var) or the result of a command (`cmd`); it must be quoted if it contains spaces or tabs. Any number of parameters can be specified.

Command-line parameters are not available until the first line of input is read, and thus cannot be accessed in the BEGIN procedure. (Older implementations of awk and nawk would process leading command-line assignments before running the BEGIN procedure. This was contrary to how things were documented in The AWK Programming Language, which says that they are processed when awk would go to open them as filenames, i.e., after the BEGIN procedure. The Bell Labs awk was changed to correct this, and the -v option was added at the same time, in early 1989. It is now part of POSIX awk.) Parameters are evaluated in the order in which they appear on the command line up until a filename is recognized. Parameters appearing after that filename will be available when the next filename is recognized.

Shell Wrapper for Invoking awk

Typing a script at the system prompt is only practical for simple, one-line scripts. Any script that you might invoke as a command and reuse can be put inside a shell script. Using a shell script to invoke awk makes the script easy for others to use.

You can put the command line that invokes awk in a file, giving it a name that identifies what the script does. Make that file executable (using the chmod command) and put it in a directory where local commands are kept. The name of the shell script can be typed on the command line to execute the awk script. This is preferred for easily used and reused scripts.

On modern UNIX systems, including Linux, you can use the #! syntax to create self-contained awk scripts:

#! /usr/bin/awk -f
script

Awk parameters and the input filename can be specified on the command line that invokes the shell script. Note that the pathname to use is system-dependent.