导出变量时,要注意Shell环境。如果在子Shell中导出变量,那么该变量只对该子Shell及其子进程有效。而如果想要在父Shell中调用该变量,则需要在父Shell中重新定义。下面是示例代码,父Shell已导出变量,但在子Shell中不能调用:
#!/bin/bash
my_var=hello
export my_var
echo "Parent Shell: Variable my_var is $my_var"
./child_script.sh
#child_script.sh
#!/bin/bash
echo "Child Shell: Variable my_var is $my_var" # my_var is not defined in this shell
要在子Shell中调用已导出的变量,可以使用“source”或“.”操作符,使子Shell能够获取父Shell环境中的变量。修改后的代码示例如下:
#!/bin/bash
my_var=hello
export my_var
echo "Parent Shell: Variable my_var is $my_var"
source child_script.sh
#child_script.sh
#!/bin/bash
echo "Child Shell: Variable my_var is $my_var"
输出结果:
Parent Shell: Variable my_var is hello
Child Shell: Variable my_var is hello