参数解析与错误处理

#!/usr/bin/env bash
# usage: ./deploy.sh <env> <app>
echo "脚本名: $0"
echo "环境:   $1"
echo "应用:   $2"
echo "参数个数: $#"

# 遍历所有参数，逐个打印（正确写法）
for arg in "$@"; do
  echo "arg=$arg"
done

# 两位数参数必须花括号
echo "${10}"
# 空参数也要保留：用 "$@" 而不是 $*
print_args() { for a in "$@"; do printf '[%s] ' "$a"; done; echo; }
print_args "a b" c "" d     # [a b] [c] [] [d]

# 参数缺省：没有就给默认
env="${1:-prod}"
app="${2:-web}"

# 参数切片：从第 2 个参数开始取全部
rest=("${@:2}")
echo "剩余参数: ${rest[*]}"

# 参数必须存在：缺失直接报错退出
: "${1:?请指定环境，用法: $0 <env>}"

# 分离"选项参数"与"普通参数"
flag="${1}"
shift
rest=("$@")           # shift 之后 $@ 只剩普通参数

# 取最后一个参数
echo "${!#}"

#!/usr/bin/env bash
# usage: ./app.sh [-a] [-b value] [-h]
verbose=0
batch=""
while getopts "ab:h" opt; do
  case "$opt" in
    a) verbose=1 ;;
    b) batch="$OPTARG" ;;
    h) echo "用法: $0 [-a] [-b value] [-h]"; exit 0 ;;
    \?) echo "非法选项"; exit 2 ;;
  esac
done
shift $((OPTIND - 1))   # 跳过已解析的选项，$@ 剩普通参数

echo "verbose=$verbose batch=$batch"
echo "剩余参数: $@"

# 选项参数缺省：用 ${OPTARG:-默认}
while getopts "p:" opt; do
  case "$opt" in
    p) port="${OPTARG:-8080}" ;;
  esac
done

# shift 基础
set -- a b c
shift
echo "$1"            # b
shift 2
echo "$1"            # 空（已全部消费完）

# 用 shift 手动解析"子命令"
command="$1"
shift
case "$command" in
  start) start_service "$@" ;;   # 剩余参数交给子命令
  stop)  stop_service "$@" ;;
  *)     echo "未知命令: $command"; exit 1 ;;
esac

# 边消费边处理
while (( $# > 0 )); do
  echo "处理: $1"
  shift
done

# read 按逗号拆分 CSV
IFS=, read -r name age city <<< "张三,25,杭州"
echo "name=$name age=$age city=$city"

# 自定义拼接：把数组拼成逗号串
arr=(a b c)
joined=$(IFS=,; echo "${arr[*]}")
echo "$joined"          # a,b,c

# 解析 /etc/passwd 冒号字段
while IFS=: read -r user pass uid gid rest; do
  echo "$user -> uid=$uid"
done < /etc/passwd

# 保留行首空格的读取
printf '  hello  \n' | { IFS= read -r line; echo "[$line]"; }

# 判空
[[ -z "$1" ]] && { echo "缺少参数"; exit 1; }

# 数字校验
[[ "$1" =~ ^[0-9]+$ ]] || { echo "必须是数字: $1"; exit 1; }

# 枚举校验
case "$1" in dev|test|prod) ;; *) echo "非法环境"; exit 1;; esac

# 文件路径校验
[[ -f "$2" ]] || { echo "文件不存在: $2"; exit 1; }

require_env() {
  local env="$1"
  case "$env" in
    dev|test|prod) return 0 ;;
    *) echo "非法环境: $env（可选 dev/test/prod）" >&2; return 1 ;;
  esac
}

require_env "${1:-}" || exit 1

# 校验后设置强类型变量（全大写全局）
readonly ENV="${1:?}"
readonly APP="${2:-web}"

# 错误处理函数
error() {
  echo "[ERROR] $(date +%F\ %T) $*" >&2
  exit "${2:-1}"
}
die() { error "$@"; }

# 使用
[[ -f "$config" ]] || die "配置文件不存在: $config"

# 保留上一条命令的退出码再退出
cmd_fail; rc=$?
[ "$rc" -ne 0 ] && { echo "失败 rc=$rc" >&2; exit $rc; }

# 检查命令是否存在
if ! command -v jq >/dev/null 2>&1; then
  echo "缺少依赖 jq" >&2
  exit 1
fi

# 忽略特定失败：临时目录清理
rm -rf "$tmp" || true