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如何正确地对$@进行赋值

 3 years ago
source link: https://www.lujun9972.win/blog/2017/01/01/%E5%A6%82%E4%BD%95%E6%AD%A3%E7%A1%AE%E5%9C%B0%E5%AF%B9$@%E8%BF%9B%E8%A1%8C%E8%B5%8B%E5%80%BC/index.html
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如何正确地对$@进行赋值

$@ 比较特殊,跟一般的 $VAR 都不一样. 当进行赋值时通常需要把 $@ 赋值给数组变量,否则在处理由引号括起来的带空格的参数时就可能会有问题了.

下面是举几个例子作为演示:

  1. 遍历 "$@" 的效果: 

    function test
{
    for var in "$@";do
        echo $var
    done
}

test 1 "2 3" 4

  2. 用一般变量commands保存 "$@",并遍历 "$commands" 

    function test
{
    commands="$@"
    for var in "$commands";do
        echo $var
    done
}

test 1 "2 3" 4

    发现所有参数都合并成一行 1 2 3 4

  3. 用一般变量commands保存 "$@",并遍历 $commands 

    function test
{
    commands="$@"
    for var in $commands;do
        echo $var
    done
}

test 1 "2 3" 4

    发现只输出中把参数 2 3 e拆分开了.

  4. 用数组变量commands保存 "$@",并遍历 "$commands" 

    function test
{
    commands=("$@")
    for var in "${commands[@]}";do
        echo $var
    done
}

test 1 "2 3" 4

    这次的结果总算是正确的了.

总结起来,要正确地对 $@ 进行赋值要注意以下几点:

  1. 使用数组变量保存 $@ 的值: 

    commands=("$@")

  2. 便利数组变量时,需要使用带引号的@进行遍历 

    for var in "${commands[@]}";do
done

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