- 01Setting up (what you'll need)
- 02Your first shell script (echo)
- 03Using variables
- 04Command-line arguments ($1, $2 ...)
- 05Branching (the if statement)
- 06Repeating (the for loop)
- 07Repeating (the while loop)
- 08Writing your own function
- 09Working with arrays
- 10Command substitution ($())
- 11Working with strings (parameter expansion)
- 12Reading from standard input (read)
- 13Exit status and && / ||
- 14Pipes and redirection
- 15The case statement
- 16Arithmetic ($(( )))
- 17The basics of grep, sed and awk
- 18Argument checks and error handling
- 19Function return values and exit codes
- 20[Project] Build a small log-tallying script
Repeating (the while loop)
This lesson covers the while statement, which repeats only while a condition holds.
Writing while [ condition ]; do ... done repeats the block for as long as the condition is true.
The sample code prints a number and increases it by one while count is 3 or less. The increment uses arithmetic expansion: count=$((count + 1)).
A common early stumble is forgetting to update the counter inside the loop and ending up in an infinite loop. Whenever you use a while statement, make sure something in the body eventually makes the condition false.
In professional work, while loops are the usual choice for retrying until a condition is met — waiting for a server to come up, for instance.
๐งช This site can't compile or run Shell Script directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser โ nothing is sent anywhere).