#!/bin/bash
i=0
(
        while (( i < 3 ))
        do
                echo hello
                i=`expr $i + 1`
                sleep 1
        done
        echo "i=$i"
)
echo "i=$i"

文件名：test1.sh
dangming@dangming-desktop:~/user/review/shell$ sh test1.sh
test1.sh: 12: cannot open 3: No such file
test1.sh: 12: i: not found
i=0
i=0
不知道错在哪里，我的ubuntu是这个结果，别人的redhat、ubu可以执行