10.1. The Importance of Functions

Functions are fundamental building blocks for creating modular, reusable, and maintainable code. A large program can be broken down into smaller, self-contained functions that perform specific tasks. AWK provides a rich library of built-in functions for common operations and also allows programmers to define their own.

10.2. Built-in Functions

AWK comes with a large set of pre-defined functions that are always available. They are generally grouped into the following categories:

• Arithmetic Functions
• String Functions
• Time Functions
• Bit Manipulation Functions
• Miscellaneous Functions

10.3. User-Defined Functions

Creating custom functions is key to managing complexity and promoting code reuse.

• General Syntax:
  • The function keyword is required.
  • function_name must begin with a letter and can contain letters, numbers, or underscores.
  • The parameter list is a comma-separated list of variable names; it can be empty.
  • The function body contains the AWK statements that execute when the function is called.

The following example, stored in a file named functions.awk, defines functions to find the minimum and maximum of two numbers and calls them from a main function.

# functions.awk

# Returns minimum number

function find_min(num1, num2){

if (num1 < num2)

return num1

return num2

}

# Returns maximum number

function find_max(num1, num2){

if (num1 > num2)

return num1

return num2

}

# Main function

function main(num1, num2){

# Find minimum number

result = find_min(10, 20)

print “Minimum =”, result

# Find maximum number

result = find_max(10, 20)

print “Maximum =”, result

}

# Script execution starts here

BEGIN {

main(10, 20)

}

Output:

Minimum = 10

Maximum = 20

After processing data internally with functions, it is often necessary to send the results to external files or commands, which we can accomplish with I/O redirection.