FreeBSD6 Unleashed

Loops

Sometimes you might want an operation to repeat until a certain condition becomes true (or until a certain condition is no longer true). This is where looping statements come into play. The Bourne shell supports three different looping constructs for these situations. These are the while loop, the until loop, and the for loop. You will look at each one separately.

The while Loop

The while loop takes a test condition as an argument, and repeats the statements inside the loop as long as the condition that is being tested is true. In other words, whatever is enclosed in the loop keeps being executed over and over until it causes a change in the program’s variables such that the test condition becomes false. If the condition is already false ...