无法让 if 语句正确运行

Question

我想检查文件是否存在，如果不存在，我想询问用户是否要创建它。无论用户输入Y还是N，屏幕上都只会出现“Whatever you say”。

#!/bin/bash

#This is testing if a file (myFile) exists

if [ -f ~/myFile  ]
then 
        echo "The file exists!"
else
        echo "The file does not exist. Would you like to create it? (Y/N)"
        read ANSWER
fi

if [ "$ANSWER"="N" ]
then
        echo "Whatever you say!"
else
        touch myFile
        echo "The file has been created!"
fi

Answer 1

=使用比较运算符时应使用空格。[ ]是一个 shell 内置函数。因此，你必须用空格传递每个参数。所以你应该这样做：

if [ "$ANSWER" = "N" ]

来源：http://www.tldp.org/LDP/abs/html/comparison-ops.html

Answer 2

您需要在=运算符周围留有空格。

if [ "$ANSWER" = "N" ]

当我需要文本匹配时，我更喜欢使用caseovertest或[ ... ]，因为它更加灵活和高效。

FILE=~/myFile
if [ -f "$FILE"  ]
then 
        echo "The file exists!"
else
        echo -n "The file does not exist. Would you like to create it? (Y/N) "
        read ANSWER
        shopt -s nocasematch
        case "$ANSWER" in
        n|no)
                echo "Whatever you say!"
                ;;
        *)
                touch "$FILE"
                echo "The file has been created!"
                ;;
        esac
        shopt -u nocasematch
fi