脚本 first (测试示例1) 
first
#!/bin/bash
echo 'your are in first file'

方法一:使用source

#!/bin/bash
echo 'your are in second file'
source first

方法二:使用.

#!/bin/bash
echo 'your are in second file'
. first

方法三:使用sh
#!/bin/bash
echo 'your are in second file'
sh  first