Linux Shells by Example

9.6. Looping Commands

Looping commands are used to execute a command or group of commands a set number of times or until a certain condition is met. The Bourne shell has three types of loops: the for loop, the while loop, and the until loop.

9.6.1. The for Command

The for looping command is used to execute commands a finite number of times on a list of items. For example, you might use this loop to execute the same commands on a list of files or usernames. The for command is followed by a user-defined variable, the keyword in, and a list of words. The first time in the loop, the first word from the wordlist is assigned to the variable, and then shifted off the list. Once the word is assigned to the variable, the body of the loop is entered, and ...