www.delorie.com/gnu/docs/gawk/gawk_106.html   search  
 
Buy the book!


The GNU Awk User's Guide

[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ]

7.4.1 The if-else Statement

The if-else statement is awk's decision-making statement. It looks like this:

 
if (condition) then-body [else else-body]

The condition is an expression that controls what the rest of the statement does. If the condition is true, then-body is executed; otherwise, else-body is executed. The else part of the statement is optional. The condition is considered false if its value is zero or the null string; otherwise, the condition is true. Refer to the following:

 
if (x % 2 == 0)
    print "x is even"
else
    print "x is odd"

In this example, if the expression `x % 2 == 0' is true (that is, if the value of x is evenly divisible by two), then the first print statement is executed; otherwise, the second print statement is executed. If the else keyword appears on the same line as then-body and then-body is not a compound statement (i.e., not surrounded by curly braces), then a semicolon must separate then-body from the else. To illustrate this, the previous example can be rewritten as:

 
if (x % 2 == 0) print "x is even"; else
        print "x is odd"

If the `;' is left out, awk can't interpret the statement and it produces a syntax error. Don't actually write programs this way, because a human reader might fail to see the else if it is not the first thing on its line.


  webmaster   donations   bookstore     delorie software   privacy  
  Copyright 2003   by The Free Software Foundation     Updated Jun 2003