Check if a package is installed or not in Arch

check_package_installed.sh

#!/usr/bin/env bash

packageName="libssl"

pacman -Qi "$packageName" &> /dev/null

if [ $? -eq 0 ]; then
  echo "Package '$packageName' is installed"
fi

if [ ! $? -eq 0 ]; then
  echo "Package '$packageName' is not installed"
fi

check_package_installed_example.sh

#!/usr/bin/env bash

isPackageInstalled() {
  pacman -Qi "$packageName" &> /dev/null
  echo $?
}

if [ isPackageInstalled('stow') ]; then
  echo 'Package is installed'
fi