1. The Linux Command Line Chapter 29
Flow Control: Looping With while / until
Prepared by Dr. Reyes, New York City College of Technology

2. while Loop
while – a command that evaluates the exit status of a list of commands, and executes the commands inside the loop as long as the exit status is zero. Stops otherwise.
Syntax:
while commands; do
commands
done

3. while Loop Example

4. Breaking Out Of A Loop
break – A command that immediately terminates a loop, and makes a program control resume with the next statement following the loop.
continue – A command that causes the remainder of the loop to be skipped, and program control resumes with the next iteration of the loop.
These commands should seldom be used.

5. The until Command
until - A command similar to the while, except that instead of exiting a loop when a nonzero exit status is encountered, it does the opposite.
An until loop continues until it receives a zero exit status
Syntax:
until commands; do
commands
done

6. until Command Example