BASH嵌套循环中exit 1无法终止程序，求问题排查方案

问题场景 #

以下Bash代码在调用error_exit执行exit 1时，无法在首次触发错误时终止整个程序，反而会继续执行后续循环：

#!/bin/bash

THIS_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
JINJANG_DIR="$(cd "$THIS_DIR/../.." && pwd)"
DATAS_DIR="$THIS_DIR/datas"

error_exit() {
    echo ""
    echo "ERROR - Following command opens the file that has raised an error."
    echo ""
    echo "  > open \"$1\""
    exit 1
}


cd "$DATAS_DIR"

find . -name 'datas.*'  -type f | sort  | while read -r datafile
do
    localdir="$(dirname $datafile)"
    
    echo "    * Testing ''$localdir''."
    
    filename=$(basename "$datafile")
    ext=${filename##*.}
    
    if [ "$ext" == "py" ]
    then
        unsafe="-u"
    else
        unsafe=""
    fi
    
    datas="$DATAS_DIR/$datafile"

    find . -name 'template.*'  -type f | sort  | while read -r template
    do
        filename=$(basename "$template")
        ext=${filename##*.}

        template="$DATAS_DIR/$template"
        outputfound="$DATAS_DIR/$localdir/output_found.$ext"
        
        cd "$JINJANG_DIR"
        python -m src $UNSAFE "$DATA" "$TEMPLATE" "$OUTPUTFOUND"  || error_exit "$localdir"
    done

    cd "$DATAS_DIR"
done

执行后输出示例：

ERROR - Following command opens the file that has raised an error.

  > open "./html/no-param-1"
    * Testing ''./html/no-param-2''.

ERROR - Following command opens the file that has raised an error.

  > open "./html/no-param-2"
    * Testing ''./latex/no-param-1''.

ERROR - Following command opens the file that has raised an error.

  > open "./latex/no-param-1"
    * Testing ''./latex/no-param-2''.

ERROR - Following command opens the file that has raised an error.

核心原因 #

管道（|）会创建子进程，while循环在子shell中执行。当你在循环里调用exit 1时，只会终止当前的子shell进程，而外层的父shell进程（执行外层循环的进程）不受影响，会继续执行下一次循环迭代。

比如代码中这两段结构：

find . -name 'datas.*'  -type f | sort  | while read -r datafile
# ...
find . -name 'template.*'  -type f | sort  | while read -r template

管道右侧的while循环都在独立的子shell里运行，exit只能退出这个子shell，无法终止整个脚本。

解决方法 #

方法1：用进程替换替代管道 #

将管道结构改成进程替换，让while循环在当前shell中执行，这样exit就能终止整个脚本。修改后的循环结构如下：

外层循环修改：

while read -r datafile
do
    # 原循环内代码不变
done < <(find . -name 'datas.*' -type f | sort)

内层循环修改：

while read -r template
do
    # 原循环内代码不变
done < <(find . -name 'template.*' -type f | sort)

额外注意：变量大小写错误 #

代码中存在变量大小写不匹配的问题，会导致python命令接收空值，需要修正：

• 定义的小写unsafe，调用时写成了$UNSAFE
• 定义的datas，调用时写成了$DATA
• 定义的template，调用时写成了$TEMPLATE
• 定义的outputfound，调用时写成了$OUTPUTFOUND

修正后的python命令：

python -m src $unsafe "$datas" "$template" "$outputfound"  || error_exit "$localdir"

内容的提问来源于stack exchange，提问作者projetmbc