Functions in Bash

Functions group commands and accept positional parameters $1, $2, …—similar spirit to Python functions but without typed signatures.

Define and call

greet() {
  echo "Hello, $1"
}
greet "Ada"
greet "Lin"

$1 is the first argument; $@ is all arguments as separate words.

Return exit status

is_even() {
  local n=$1
  (( n % 2 == 0 ))
}
if is_even 4; then echo "even"; else echo "odd"; fi

Functions return the exit status of the last command—use return N explicitly when needed.

local variables

counter=0
bump() {
  local counter=1
  counter=$((counter + 1))
  echo "inside: $counter"
}
bump
echo "outside: $counter"

local avoids clobbering outer variables—good habit in larger scripts.

Important interview questions and answers

1. Q: How do functions receive args?
   A: Positional parameters $1, $2, … and $@ for all.
2. Q: What does local do?
   A: Creates a variable scoped to the function body.

Self-check

1. What variable holds the first argument?
2. How does a function signal success/failure without print?

Tip: Use local for temporaries—compare with Python local scope habits from Python.