The GAWK Manual

Edition 0.15, April 1993

• Preface
  • History of awk and gawk
• GNU GENERAL PUBLIC LICENSE
  • Preamble
  • TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
  • How to Apply These Terms to Your New Programs
• Using this Manual
  • Data Files for the Examples
• Getting Started with awk
  • A Very Simple Example
  • An Example with Two Rules
  • A More Complex Example
  • How to Run awk Programs
    • One-shot Throw-away awk Programs
    • Running awk without Input Files
    • Running Long Programs
    • Executable awk Programs
  • Comments in awk Programs
  • awk Statements versus Lines
  • When to Use awk
• Reading Input Files
  • How Input is Split into Records
  • Examining Fields
  • Non-constant Field Numbers
  • Changing the Contents of a Field
  • Specifying how Fields are Separated
  • Reading Fixed-width Data
  • Multiple-Line Records
  • Explicit Input with getline
  • Closing Input Files and Pipes
• Printing Output
  • The print Statement
  • Examples of print Statements
  • Output Separators
  • Controlling Numeric Output with print
  • Using printf Statements for Fancier Printing
    • Introduction to the printf Statement
    • Format-Control Letters
    • Modifiers for printf Formats
    • Examples of Using printf
  • Redirecting Output of print and printf
    • Redirecting Output to Files and Pipes
    • Closing Output Files and Pipes
  • Standard I/O Streams
• Useful "One-liners"
• Patterns
  • Kinds of Patterns
  • Regular Expressions as Patterns
    • How to Use Regular Expressions
    • Regular Expression Operators
    • Case-sensitivity in Matching
  • Comparison Expressions as Patterns
  • Boolean Operators and Patterns
  • Expressions as Patterns
  • Specifying Record Ranges with Patterns
  • BEGIN and END Special Patterns
  • The Empty Pattern
• Overview of Actions
• Expressions as Action Statements
  • Constant Expressions
  • Variables
    • Assigning Variables on the Command Line
  • Arithmetic Operators
  • String Concatenation
  • Comparison Expressions
  • Boolean Expressions
  • Assignment Expressions
  • Increment Operators
  • Conversion of Strings and Numbers
  • Numeric and String Values
  • Conditional Expressions
  • Function Calls
  • Operator Precedence (How Operators Nest)
• Control Statements in Actions
  • The if Statement
  • The while Statement
  • The do-while Statement
  • The for Statement
  • The break Statement
  • The continue Statement
  • The next Statement
  • The next file Statement
  • The exit Statement
• Arrays in awk
  • Introduction to Arrays
  • Referring to an Array Element
  • Assigning Array Elements
  • Basic Example of an Array
  • Scanning all Elements of an Array
  • The delete Statement
  • Using Numbers to Subscript Arrays
  • Multi-dimensional Arrays
  • Scanning Multi-dimensional Arrays
• Built-in Functions
  • Calling Built-in Functions
  • Numeric Built-in Functions
  • Built-in Functions for String Manipulation
  • Built-in Functions for Input/Output
  • Functions for Dealing with Time Stamps
• User-defined Functions
  • Syntax of Function Definitions
  • Function Definition Example
  • Calling User-defined Functions
  • The return Statement
• Built-in Variables
  • Built-in Variables that Control awk
  • Built-in Variables that Convey Information
• Invoking awk
  • Command Line Options
  • Other Command Line Arguments
  • The AWKPATH Environment Variable
  • Obsolete Options and/or Features
  • Undocumented Options and Features
• The Evolution of the awk Language
  • Major Changes between V7 and S5R3.1
  • Changes between S5R3.1 and S5R4
  • Changes between S5R4 and POSIX awk
  • Extensions in gawk not in POSIX awk
• Installing gawk
  • The gawk Distribution
    • Getting the gawk Distribution
    • Contents of the gawk Distribution
  • Compiling and Installing gawk on Unix
    • Compiling gawk for a Supported Unix Version
    • The Configuration Process
    • Configuring gawk for a New System
  • Compiling, Installing, and Running gawk on VMS
    • Compiling gawk under VMS
    • Installing gawk on VMS
    • Running gawk on VMS
    • Building and using gawk under VMS POSIX
  • Installing gawk on MS-DOS
  • Installing gawk on the Atari ST
• gawk Summary
  • Command Line Options Summary
  • Language Summary
  • Variables and Fields
    • Fields
    • Built-in Variables
    • Arrays
    • Data Types
  • Patterns and Actions
    • Patterns
    • Regular Expressions
    • Actions
      • Operators
      • Control Statements
      • I/O Statements
      • printf Summary
      • Special File Names
      • Numeric Functions
      • String Functions
      • Built-in time functions
      • String Constants
  • Functions
  • Historical Features
• Sample Program
• Reporting Problems and Bugs
• Implementation Notes
  • Downward Compatibility and Debugging
  • Probable Future Extensions
  • Suggestions for Improvements
• Glossary
• Index