Also auto-install nmap if it's missing.

Author: postmodern

scripts/setup

@@ -45,6 +45,109 @@ function fail()
 	exit -1
 }
 
+#
+# Sets os_platform and os_arch.
+#
+function detect_os()
+{
+	os_platform="$(uname -s)"
+	os_arch="$(uname -m)"
+}
+
+#
+# Auto-detect the package manager.
+#
+function detect_package_manager()
+{
+	case "$os_platform" in
+		Linux)
+			if [[ -f /etc/redhat-release ]]; then
+				if   command -v dnf >/dev/null; then
+					package_manager="dnf"
+				elif command -v yum >/dev/null; then
+					package_manager="yum"
+				fi
+			elif [[ -f /etc/debian_version ]]; then
+				if command -v apt-get >/dev/null; then
+					package_manager="apt"
+				fi
+			elif [[ -f /etc/SuSE-release ]]; then
+				if command -v zypper >/dev/null; then
+					package_manager="zypper"
+				fi
+			elif [[ -f /etc/arch-release ]]; then
+				if command -v pacman >/dev/null; then
+					package_manager="pacman"
+				fi
+			elif [[ -f /etc/os-release ]]; then
+				if command -v pacman >/dev/null; then
+					package_manager="pacman"
+				elif command -v zypper >/dev/null; then
+					package_manager="zypper"
+				fi
+			elif [[ "$HOME" == *"com.termux"* ]]; then
+				package_manager="termux"
+			fi
+			;;
+		Darwin)
+			if   command -v brew >/dev/null; then
+				package_manager="brew"
+			elif command -v port >/dev/null; then
+				package_manager="port"
+			fi
+			;;
+		*BSD)
+			if command -v pkg >/dev/null; then
+				package_manager="pkg"
+			fi
+			;;
+	esac
+}
+
+#
+# Detects the system.
+#
+function detect_system()
+{
+	detect_os
+	detect_package_manager
+}
+
+#
+# Installs a list of package names using the detected package manager.
+#
+function install_packages()
+{
+	case "$package_manager" in
+		apt)	$sudo apt-get install -y "$@" || return $? ;;
+		dnf|yum)$sudo $package_manager install -y "$@" || return $?     ;;
+		port)   $sudo port install "$@" || return $?       ;;
+		pkg)	$sudo pkg install -y "$@" || return $?     ;;
+		brew)
+			local brew_owner="$(/usr/bin/stat -f %Su "$(command -v brew)")"
+			sudo -u "$brew_owner" brew install "$@" ||
+			sudo -u "$brew_owner" brew upgrade "$@" || return $?
+			;;
+		pacman)
+			local missing_pkgs=($(pacman -T "$@"))
+
+			if (( ${#missing_pkgs[@]} > 0 )); then
+				$sudo pacman -Sy --noconfirm "${missing_pkgs[@]}" || return $?
+			fi
+			;;
+		zypper) $sudo zypper -n in -l $* || return $? ;;
+		termux)	pkg install -y "$@" || return $? ;;
+		"")	warn "Could not determine Package Manager. Proceeding anyway." ;;
+	esac
+}
+
+if ! command -v nmap >/dev/null; then
+	detect_system
+
+	log "Installing nmap ..."
+	install_packages nmap || warn "Could not install nmap. Proceeding anyways ..."
+fi
+
 # default to installing gems into vendor/bundle
 if [[ ! -f .bundle/config ]]; then
 	bundle config set --local path vendor/bundle >/dev/null || \