03-functions

03 · Functions

Maps to Shell Scripting → Section 4: Functions (defining functions, parameters, local variables, reusable logic)

Functions turn a long script into named, reusable building blocks - deploy, rollback, notify. Same idea as functions anywhere: define once, call many times, pass in parameters.

How to use this set

make start  S=03-functions
#   ...work in the container; when done, type 'exit' (or Ctrl+D) to leave, then:
make verify S=03-functions
make reset  S=03-functions

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Tier 1 - Define & call (hint: name() { ... }, then call it by name)

1.1 (graded) Write ~/sandbox/hello-fn.sh that defines a function which prints Hello from a function, then calls it.

Tier 2 - Functions with parameters (think: inside a function, $1 is its first arg)

2.1 (graded) Write ~/sandbox/square.sh with a function that takes a number and prints its square. The script passes its own first parameter to the function - so ./square.sh 6 prints 36.

2.2 (graded) Write ~/sandbox/greet-fn.sh with a function that takes a name and prints Hi, <name>; the script passes $1 to it - ./greet-fn.sh Sam → Hi, Sam.

Tier 3 - A function with its own logic (goal only)

3.1 (graded) Write ~/sandbox/maxof.sh with a max function that takes two numbers and prints the larger one (decide inside the function). The script passes $1 and $2 - ./maxof.sh 3 8 → 8.

Self-check questions

1. What are the two ways to define a function in bash, and how do you call it?
2. Inside a function, how do you read the arguments it was called with?
3. Why use local for a variable inside a function?