将参数中命名的变量更改为bash函数 [英] Change variable named in argument to bash function

问题描述

在我的bash脚本中，我经常提示用户输入y/n答案.由于我经常在单个脚本中多次使用此命令，因此我希望有一个函数来检查用户输入是否为Yes/No的某种变体，然后将此答案清除为"y"或"n".像这样:

In my bash scripts, I often prompt users for y/n answers. Since I often use this several times in a single script, I'd like to have a function that checks if the user input is some variant of Yes / No, and then cleans this answer to "y" or "n". Something like this:

yesno(){
    temp=""
    if [[ "$1" =~ ^([Yy](es|ES)?|[Nn][Oo]?)$ ]] ; then
        temp=$(echo "$1" | tr '[:upper:]' '[:lower:]' | sed 's/es//g' | sed 's/no//g')
        break
    else
        echo "$1 is not a valid answer."
    fi
}

然后我想按如下方式使用该函数:

I then would like to use the function as follows:

while read -p "Do you want to do this? " confirm; do # Here the user types "YES"
    yesno $confirm
done
if [[ $confirm == "y" ]]; then
    [do something]
fi

基本上，我想将第一个参数的值更改为 $ confirm 的值，以便当我退出 yesno 函数时， $ confirm是"y"或"n".

Basically, I want to change the value of the first argument to the value of $confirm, so that when I exit the yesno function, $confirm is either "y" or "n".

我尝试在 yesno 函数中使用 set-"$ temp" ，但无法正常工作.

I tried using set -- "$temp" within the yesnofunction, but I can't get it to work.

推荐答案

您可以通过输出新值并覆盖调用方中的变量来做到这一点.

You could do it by outputting the new value and overwriting the variable in the caller.

yesno() {
    if [[ "$1" =~ ^([Yy](es|ES)?|[Nn][Oo]?)$ ]] ; then
        local answer=${1,,}
        echo "${answer::1}"
    else
        echo "$1 is not a valid answer." >&2
        echo "$1"  # output the original value
        return 1   # indicate failure in case the caller cares
    fi
}

confirm=$(yesno "$confirm")

但是，我建议一种更直接的方法:让该函数执行提示和循环.将所有重复的逻辑移到内部.那么呼叫站点非常简单.

However, I'd recommend a more direct approach: have the function do the prompting and looping. Move all of that repeated logic inside. Then the call site is super simple.

confirm() {
    local prompt=$1
    local reply

    while true; do
        read -p "$prompt" reply

        case ${reply,,} in
            y*) return 0;;
            n*) return 1;;
            *)  echo "$reply is not a valid answer." >&2;;
        esac
    done
}

if confirm "Do you want to do this? "; then
    # Do it.
else
    # Don't do it.
fi

(( $ {reply，} 是一种bash行为，将 $ reply 转换为小写.)

(${reply,,} is a bash-ism that converts $reply to lowercase.)

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