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  • Shell脚本之:if-else

    Shell 有三种 if ... else 语句:

    1.if ... fi 语句;

    2.if ... else ... fi 语句;

    3.if ... elif ... else ... fi 语句。

    if ... fi 语句

    if ... else 语句的语法:

    if [ expression ]
    then
       Statement(s) to be executed if expression is true
    fi

    注意:expression 和方括号([ ])之间必须有空格,否则会有语法错误。

    if ... 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 ... else ... fi 语句

    if ... elif ... else ... fi 语句的语法

    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

    配合test的if-else语句

    if ... else 语句也经常与 test 命令结合使用,如下所示:

    num1=1
    num2=2
    if test ${num1} -eq ${num2}
    then
        echo 'The two numbers are equal!'
    else
        echo 'The two numbers are not equal!'
    fi
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  • 原文地址:https://www.cnblogs.com/runnyu/p/4676660.html
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