Question

我编写了一个函数来将是或否的答案转换为true或false（0或1）。但是我找不到命令＆＃39;每次运行脚本时都会出错。请帮我解决问题

get_boolean(){
    #==============================================================================================
    # Returns false if the first argument is NO and returns true if it is YES.
    # If the first argument is not a valid YES or NO,
    # then the return value depends on the default specified by argument 2 (Default value)
    #==============================================================================================

    if [ "$1" == 'NO' ] || [ "$1" == 'no' ] || [ "$1" == 'No' ] || [ "$1" == 'N' ] || [ "$1" == 'n' ]; then
            return 1;
    elif [ "$1" == 'YES' ] || [ "$1" == 'yes' ] || [ "$1" == 'Yes' ] || [ "$1" == 'Y' ] || [ "$1" == 'y' ]; then
            return 0;
    elif [ "$2" == 'NO' ] || [ "$2" == 'no' ] || [ "$2" == 'No' ] || [ "$2" == 'N' ] || [ "$2" == 'n' ]; then
            return 1;
    elif [ "$2" == 'YES' ] || [ "$2" == 'yes' ] || [ "$2" == 'Yes' ] || [ "$2" == 'Y' ] || [ "$2" == 'y' ]; then
            return 0;
    fi
}

read -p 'Do you want to drop the table of invalids? [n]:' DROP_TABLE_OF_INVALIDS
echo "After read: $DROP_TABLE_OF_INVALIDS"
DROP_TABLE_OF_INVALIDS=get_boolean "$DROP_TABLE_OF_INVALIDS" 'n'
echo "After assignment: $DROP_TABLE_OF_INVALIDS"
if $DROP_TABLE_OF_INVALIDS; then
        echo "Hello. I will drop the table"
fi

当我运行脚本时，我收到了这些错误：

bash-3.2$ sh test.sh
Do you want to drop the table of invalids? [n]:y
After read: y
test.sh: line 24: y: command not found
After assignment: y
test.sh: line 26: y: command not found
bash-3.2$ sh test.sh
Do you want to drop the table of invalids? [n]:n
After read: n
test.sh: line 24: n: command not found
After assignment: n
test.sh: line 26: n: command not found

更新：以下代码有效（感谢Barmar！）

get_boolean(){
        #==============================================================================================
        # Outputs false if the first argument is NO and outputs true if it is YES.
        # If the first argument is not a valid YES or NO,
        # then the output value depends on the default specified by argument 2 (Default value)
        #==============================================================================================

        if [ "$1" == 'NO' ] || [ "$1" == 'no' ] || [ "$1" == 'No' ] || [ "$1" == 'N' ] || [ "$1" == 'n' ]; then
                        echo false;
        elif [ "$1" == 'YES' ] || [ "$1" == 'yes' ] || [ "$1" == 'Yes' ] || [ "$1" == 'Y' ] || [ "$1" == 'y' ]; then
                        echo true;
        elif [ "$2" == 'NO' ] || [ "$2" == 'no' ] || [ "$2" == 'No' ] || [ "$2" == 'N' ] || [ "$2" == 'n' ]; then
                        echo false;
        elif [ "$2" == 'YES' ] || [ "$2" == 'yes' ] || [ "$2" == 'Yes' ] || [ "$2" == 'Y' ] || [ "$2" == 'y' ]; then
                        echo true;
        fi
}

read -p 'Do you want to drop the table of invalids? [n]:' DROP_TABLE_OF_INVALIDS
echo "After read: $DROP_TABLE_OF_INVALIDS"
DROP_TABLE_OF_INVALIDS=$(get_boolean "$DROP_TABLE_OF_INVALIDS" 'n')
echo "After assignment: $DROP_TABLE_OF_INVALIDS"
if $DROP_TABLE_OF_INVALIDS; then
                echo "Hello. I will drop the table"
fi

以下是使其有效的编辑内容：

功能＆＃39; echo而不是返回。
输出值为bash true或false（用于测试if，否则获取0：命令未找到或1：命令未找到）
函数调用包含在＆＃39; $（＆＃39;和＆＃39;）＆＃39;

Answer 1

语法：

DROP_TABLE_OF_INVALIDS=get_boolean "$DROP_TABLE_OF_INVALIDS" 'n'

表示在执行命令“$ DROP_TABLE_OF_INVALIDS”'n'“时将环境变量DROP_TABLE_OF_INVALIDS设置为字符串"get_boolean"。

使用函数输出分配变量的方法是：

DROP_TABLE_OF_INVALIDS=$(get_boolean "$DROP_TABLE_OF_INVALIDS" 'n')

此外，您需要将功能更改为使用echo而不是return。 return设置退出状态，而不是函数的输出。

Answer 2

有几个问题。这条线

DROP_TABLE_OF_INVALIDS=get_boolean "$DROP_TABLE_OF_INVALIDS" 'n'

不会致电get_boolean。它尝试使用已修改的环境运行DROP_TABLE_OF_INVALIDS命名的命令。你会想要：

DROP_TABLE_OF_INVALIDS=$(get_boolean "$DROP_TABLE_OF_INVALIDS" 'n')

这导致了第二个问题，即DROP_TABLE_OF_INVALIDS包含get_boolean的标准输出，但您使用的是返回值。试着这样称呼：

if get_boolean "$DROP_TABLE_OF_INVALIDS" 'n'; then
    ...
fi

其中返回值是测试目录，而不是捕获要测试的字符串。

第三个问题是你尝试返回一个空字符串。 return语句只能返回一个数值;它不像其他语言中的函数，它返回任意值。如果第一个参数为空，则需要确定它是真还是假; false似乎是一个很好的默认值，所以返回0.或者，你可以忽略它将它视为使用$2的值的情况。

更简单的版本是

get_boolean(){
    #==================================================================================
    # Returns false if the first argument is NO and returns true if it is YES.
    # If the first argument is not a valid YES or NO,
    # then the return value depends on the default specified by argument 2 (Default value)
    #==================================================================================
    case $1 in
        NO|No|no|N|n|"" ) return 1 ;;
        YES|yes|Yes|Y|y) return 0;;
        * ) case $2 in
            YES|yes|Yes|Y|y) return 0;;
            * ) return 1 ;;
            esac ;;
    esac
}

测试返回值：找不到命令

2 个答案: