Docker运行Shell脚本报错：unexpected "(" (expecting "}")排查

尝试使用Docker运行Shell脚本，Dockerfile内容如下：

FROM alpine
COPY . .
RUN chmod +x ./scripts/sanity-checks.sh
ENTRYPOINT ["./scripts/sanity-checks.sh"]

运行时出现错误：

./scripts/sanity-checks.sh: scripts/util.sh: line 225: syntax error: unexpected "(" (expecting "}")

util.sh中对应代码片段为：

...  
# delete the lines between and including 2 comment lines, or the comment lines themselves only
    delete_lines_for_file() {
      file_name=$1
      delete_string_start=$2
      delete_string_end=$3
      delete_comments_only=$4
      # find the start and end lines where we want to delete blocks of code
      line_num_start=$(grep -n "$delete_string_start" $file_name | awk -F  ":" '{print $1}')
      line_num_end=$(grep -n "$delete_string_end" $file_name | awk -F  ":" '{print $1}')
      line_start_arr=($line_num_start) ### LINE 225 ###
...

该脚本在本地直接运行正常，请问报错原因是什么？

• 核心原因：Alpine Linux默认使用ash shell，而你本地运行脚本用的是bash。ash不支持line_start_arr=($line_num_start)这种bash风格的数组初始化语法，因此触发语法错误。
• 解决办法：
  1. 切换到带bash的基础镜像：
     • 方案一：使用debian镜像（自带bash）

       FROM debian:stable-slim
       COPY . .
       RUN chmod +x ./scripts/sanity-checks.sh
       ENTRYPOINT ["./scripts/sanity-checks.sh"]
       

     • 方案二：在Alpine中安装bash

       FROM alpine
       RUN apk add --no-cache bash
       COPY . .
       RUN chmod +x ./scripts/sanity-checks.sh
       ENTRYPOINT ["bash", "./scripts/sanity-checks.sh"]
       

  2. 修改脚本适配ash：如果坚持使用ash，需要调整数组相关语法，比如用set命令实现变量拆分：

     # 替换原数组初始化行
     set -- $line_num_start
     line_start_arr=("$@")
     

内容的提问来源于stack exchange，提问作者snack-overthrow