•Arnošt Havelka
Premium: Bash Script Automation
Combine loops and conditionals to build scripts that run tasks automatically and respond to system state.
Start Interactive Lesson
Loops and conditionals are the backbone of automation. Master them and you'll write scripts that handle complex workflows effortlessly.
Step 1: Loop Over a List
Command Prompt
web
app
db
C:\Users\User>echo web
echo app
echo db
The for loop iterates over a list. One line replaces three.
Step 2: Loop Over Files
Command Prompt
app.log
system.log
C:\Users\User>ls *.log
Process files in batch. No need to run commands individually.
Step 3: Conditional Execution
Command Prompt
Proceed
C:\Users\User>retries=4
echo 'Proceed'
Conditionals let your script make decisions. Check file existence, compare numbers, test conditions.
Checklist You Can Reuse
- Loop with
for var in list; do commands; done. - Use
for file in *.extto process files in batch. - Test with
if [ condition ]; then commands; fi. - Comparisons:
-eq(equal),-gt(greater),-lt(less),-f(file exists).
Knowledge Check
1 / 2Which loop structure processes every .sh file in the current directory?
References
These documentation links provide authoritative details for the commands used in this article.