zsh - 用默认值读取用户输入 - 空输入不为空？

Question

我写了询问类似这样的用户输入的功能：

function is_confirmed { 

    read -rs -k 1 ans 

    if [[ "${ans}" == "n" || "${ans}" == "N" ]]; then 
     printf "No\n" 
     return 1 
    fi 

    if [[ "${ans}" == "y" || "${ans}" == "Y" ]]; then 
     printf "Yes\n" 
     return 0 
    fi 

    # here is my actual problem!!! this doesnt work when user input is blank! 
    if [[ "${ans}" == "" ]]; then 
     printf "Yes!\n" 
     return 1 
    fi 

    # Output is Damn! 
    printf "Damn" 
    return 1 
} 

的伟大工程，到目前为止，不过，我想设置成“yes”作为默认answear，所以当用户输入什么，只是按下回车，它应该回落到“是”，所以我尝试了|| "$ans" == ""但仍然回落到“该死”

怎么回事？当我在echo $ans它是空的函数的结尾......

编辑1：

这是发生了什么：

e_ask "Are you sure you want to install?\nWarning: This may override some files in your home directory." 

if is_confirmed; then 
    echo "Great!" 
else 
    e_error "Aborting..." 
fi 

这里的功能是：

function e_ask { 
    printf "\n$1\n" 
    printf "(Y/n): " 
} 

function e_warn { 
    printf "Warning: $1\n" 
} 

function e_error { 
    printf "Error: $1\n" 
    exit 1 
} 

Answer 1

A case比较好，当你想考虑许多不同的值和默认值时

function is_confirmed { 

    read -rs -k 1 ans 

    case "${ans}" in 
    y|Y|$'\n') 
     printf "Yes\n" 
      return 0 
     ;; 

    *) # This is the default 
     printf "No\n" 
      return 1 

    esac 

}

Answer 2

问题在于如何使用内建的[[编写条件。

您需要更改条件：

function is_confirmed { 

    read -rs -k 1 ans 

    if [[ "${ans}" == "n" ]] || [[ "${ans}" == "N" ]]; then 
     printf "No\n" 
     return 1 
    else if [[ "${ans}" == "y" ]] || [[ "${ans}" == "Y" ]]; then 
     printf "Yes\n" 
     return 0 
    else if [[ -z "${ans}" ]]; then 
     printf "Empty\n" 
    else 
     printf "Damn\n" 
    fi 

    return 1 
} 

为了解释，该[[内置的测试只是一个条件，但你可以&&和||的[[链的多个实例。相反，您的代码试图在[[内测试2个条件，并使用||，因为它是C/C++的用法。在help [[或man bash

Answer 3

可用

更多细节只添加的功能开始默认变量：

function is_confirmed { 

    ans="y" 

    echo "Put your choice:" 
    read $ans 


} 

如果没有被键入，默认值将保持不变。