Document installation and validate shell scripts

install.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)
+SOURCE_SCRIPT="${SCRIPT_DIR}/iptables-forward.sh"
+TARGET_BIN=${INSTALL_TARGET:-/usr/local/bin/iptables-forward}
+
+usage() {
+  cat <<USAGE
+用法:
+  sudo ./install.sh
+  sudo ./install.sh --uninstall
+
+说明:
+  - 仅创建符号链接，不复制源码。
+  - 默认链接到 /usr/local/bin/iptables-forward。
+  - 可通过 INSTALL_TARGET 自定义目标路径。
+USAGE
+}
+
+require_root() {
+  if (( EUID != 0 )); then
+    printf '请使用 root 或 sudo 执行安装脚本。\n' >&2
+    exit 2
+  fi
+}
+
+install_link() {
+  [[ -f ${SOURCE_SCRIPT} ]] || {
+    printf '未找到入口脚本: %s\n' "${SOURCE_SCRIPT}" >&2
+    exit 1
+  }
+  mkdir -p "$(dirname -- "${TARGET_BIN}")"
+  ln -sfn "${SOURCE_SCRIPT}" "${TARGET_BIN}"
+  chmod 755 "${SOURCE_SCRIPT}"
+  printf '已创建链接: %s -> %s\n' "${TARGET_BIN}" "${SOURCE_SCRIPT}"
+}
+
+uninstall_link() {
+  if [[ -L ${TARGET_BIN} || -e ${TARGET_BIN} ]]; then
+    rm -f "${TARGET_BIN}"
+    printf '已删除链接: %s\n' "${TARGET_BIN}"
+  else
+    printf '未发现已安装链接: %s\n' "${TARGET_BIN}"
+  fi
+}
+
+main() {
+  case ${1:-install} in
+    --help|-h)
+      usage
+      ;;
+    install)
+      require_root
+      install_link
+      ;;
+    --uninstall|uninstall)
+      require_root
+      uninstall_link
+      ;;
+    *)
+      usage >&2
+      exit 1
+      ;;
+  esac
+}
+
+main "$@"