Bash Functions Shell Script | Arguments & local

Long scripts become maintainable when each step is a function with a clear name and exit code. This template shows argument passing, local variables, and a pattern you can lift into backup or deploy automation.

What this script does

Defines small functions with explicit responsibilities
Uses local to avoid clobbering global variables
Propagates failures with return and set -e
Accepts --env style flags via simple parsing (see getopts post for full CLI)
Logs each stage with timestamps

Prerequisites

Bash 4+ on Linux
Git or app directory paths adjusted to your server
Run as deploy user with required permissions

Step 1: Save the script

sudo nano /usr/local/bin/deploy-app.sh
sudo chmod +x /usr/local/bin/deploy-app.sh

Step 2: Full script (scroll to read)

deploy-app.sh

#!/usr/bin/env bash
set -euo pipefail

APP_DIR="/var/www/app"
ENV_NAME="prod"

log(){ echo "[$(date '+%F %T')] $*"; }

usage(){ echo "usage: $0 [--env prod|staging]"; exit 1; }

pull_repo(){
  log "pull_repo: fetching origin/main"
  git -C "$APP_DIR" fetch --prune origin
  git -C "$APP_DIR" checkout main
  git -C "$APP_DIR" pull --ff-only origin main
}

run_migrations(){
  log "run_migrations: running"
  # php artisan migrate --force  OR  ./manage.py migrate --noinput
  log "run_migrations: OK"
}

main(){
  pull_repo
  run_migrations
  log "deploy completed ($ENV_NAME)"
}

while [[ $# -gt 0 ]]; do
  case "$1" in
    --env) ENV_NAME="${2:?}"; shift 2 ;;
    -h|--help) usage ;;
    *) usage ;;
  esac
done

main

Scroll inside the box to read the full script.

Step 3: Configure settings

Replace APP_DIR and git pull with your stack
Pair with shell scripting guide
For strict CLI flags use our getopts wrapper post in this series

Bash functions shell script with reusable deploy steps

Step 4: Test manually

./deploy-app.sh --env staging

echo exit=$?

Bash Functions Shell Script: Reusable Blocks, Arguments and local Variables