How does the while command work in Linux with examples

The while command in Linux is used to execute a loop repeatedly as long as a specified condition evaluates to true. It is commonly used in shell script

• The condition is evaluated before each iteration.
• If the condition is true, the loop executes the commands inside do and done.
• The loop stops when the condition becomes false.

Examples

1. Basic While Loop

Print numbers from 1 to 5:

Output:

2. Infinite While Loop

To create an infinite loop:

• The condition true always evaluates to true.
• Use Ctrl+C to terminate the loop.

3. Using While with Read (Reading a File Line by Line)

• This reads file.txt line by line and prints each line.

4. Using While Loop with a Command Output

Printing system processes:

• The loop reads each line of the ps -e command output and prints it.

5. While Loop with User Input

• The loop keeps asking for user input until 0 is entered.

Conclusion

• while loops are useful for running commands repeatedly based on a condition.
• They are widely used in automation, file processing, and interactive scripts