Practical Shell Scripting Basics

#!/bin/bash
set -euo pipefail

main() {
 echo " when"
}

main "$@"

NAME="SecuThive"
echo ", $NAME"
echo ': $NAME' # Single quotes preserve the literal string

readonly VERSION="1.0.0"
PORT="${PORT:-8080}"       # Default value

SERVERS=("web1" "web2" "web3")
echo "${SERVERS[0]}"       # web1
echo "${#SERVERS[@]}"      # Number of elements

FILE="/etc/nginx/nginx.conf"

if [[ -f "$FILE" ]]; then
 echo "file "
elif [[ -d "$FILE" ]]; then
 echo ""
else
 echo ""
fi

if [[ "$ENV" == "production" ]]; then
 echo " "
fi

if [[ $COUNT -gt 10 ]]; then
 echo "10 "
fi

for server in "${SERVERS[@]}"; do
 echo ": $server"
  ssh "$server" "sudo systemctl restart myapp"
done

for i in {1..5}; do
 echo "when $i"
done

COUNT=0
while [[ $COUNT -lt 3 ]]; do
 echo " ..."
  sleep 1
  ((COUNT++))
done

log() {
  local level="$1"
  local msg="$2"
  echo "[$(date '+%Y-%m-%d %H:%M:%S')] [$level] $msg"
}

check_service() {
  local service="$1"
  if systemctl is-active --quiet "$service"; then
 log "INFO" "$service run "
    return 0
  else
 log "ERROR" "$service "
    return 1
  fi
}

check_service nginx || exit 1

if ! rsync -av /src/ user@host:/dest/; then
 log "ERROR" "rsync failed"
 exit 1
fi

TMPFILE=$(mktemp)
trap 'rm -f "$TMPFILE"; echo " "' EXIT
trap 'echo " : $LINENO"' ERR