linux - 为什么我无法使用此 linux shell 脚本检测文件是否存在？

Question

我有以下代码来检测文件是否存在:

#!/bin/bash
VAR="/home/$USER/MyShellScripts/sample.txt"
if [ -e '$VAR' ]
        then
                echo "$VAR exist"
        else
                echo "the file $VAR doesn't exist!"
fi

if [ -x '$VAR' ]
        then
                echo "You have permissions to execute the file $VAR"
        else
                echo "You do not have permissions to execute the file $VAR"
fi

当我在指定目录上应用 ls 命令时，我看到:

MyLAPTOP:~/MyShellScripts$ ls
exercise_4.sh  exercise_4Original.sh  first.sh  sample.txt  second.sh

那么，如果文件存在于指定目录下，为什么检测不到呢？在脚本输出下方:

MyLAPTOP:~/MyShellScripts$ ./exercise_4.sh
the file /home/username/MyShellScripts/sample.txt doesn't exist!
You do not have permissions to execute the file /home/username/MyShellScripts/sample.txt

Answer 1

那是因为您在 if 中使用的是 '$VAR' 而不是 "$VAR"。请尝试使用 "$VAR"。单引号 ('') 内的 $VAR 将被解释为普通字符串，不会解析为您的变量。

要查看差异，请尝试以下操作:

input          output
-------------- --------------------------------------------------
echo "$VAR"    /home/<your_username>/MyShellScripts/sample.txt
echo '$VAR'    $VAR