#!/bin/bash
echo "outside subshell=$BASH_SUBSHELL"
var1=a
(
echo "inside subshell=$BASH_SUBSHELL"
var2=b
echo "from subshell \"var2\" = $var2"
echo "from subshell \"var1\" = $var1"
)
if [ -z "$var2" ]
then
echo "var2 undefined in main body of shell"
else
echo "var2 defined in main body of shell "
fi
echo "from main body 0f shell \"var2\" = $var2"
exit 0
执行输出
outside subshell=0
inside subshell=1
from subshell "var2" = b
from subshell "var1" = a
var2 undefined in main body of shell
from main body 0f shell "var2" =
小括号开启了子shell，子shell里定义的变量无法被该子shell所在的父shell(脚本运行时开启的shell)识别，可以当作局部变量