【shell】if语句

if语句

if 语句通过关系运算符判断表达式的真假来决定执行哪个分支。Shell 有三种 if ... else 语句：

 if ... fi 语句；
 if ... else ... fi 语句；
 if ... elif ... else ... fi 语句。

 

if ... else ... fi 语句的语法：

if [ expression ]
then
   Statement(s) to be executed if expression is true
else
   Statement(s) to be executed if expression is not true
fi

 

 if ... elif ... fi 语句可以对多个条件进行判断，语法：

if [ expression 1 ]
then
   Statement(s) to be executed if expression 1 is true
elif [ expression 2 ]
then
   Statement(s) to be executed if expression 2 is true
elif [ expression 3 ]
then
   Statement(s) to be executed if expression 3 is true
else
   Statement(s) to be executed if no expression is true
fi

参考资料

• shell条件判断if语句