Bash Functions & Local Scoping

Function declaration, the local keyword, and return exit codes vs stdout

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Functions modularize shell scripts. By default, all variables in Bash are global unless explicitly declared with the local keyword.

Writing Clean Shell Functions

Declare functions using function_name() { ... }.

Parameters: Inside functions, $1, $2 refer to the arguments passed to the function (NOT the script arguments).

The local keyword: Always declare internal variables with local var="value" to prevent contaminating the global shell environment.

return: Returns an integer exit status (0-255). To "return" data strings, use echo and capture output via $(func).

Function with Local Variables and Return Values

Try It Yourself »

#!/usr/bin/env bash

log_message() {
    local level="$1"
    local message="$2"
    local timestamp=$(date "+%Y-%m-%d %H:%M:%S")

    echo "[$timestamp] [$level] $message"
}

log_message "INFO" "Deploying microservice cluster..."
log_message "SUCCESS" "Cluster is online and healthy."

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Set your Publisher ID in src/config/ads.ts to display live ads.

Test Yourself With Exercise

+15 XP

What happens if you do NOT use the `local` keyword when declaring a variable inside a Bash function?

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