Bash 验证和条件语句

Question

我正在为 bash 中的程序编写安装脚本。安装的第一部分检测程序是否已安装。这是通过指定目录中是否存在文件来检测的。那部分工作正常。但是，我希望用户能够在旧版本存在的情况下升级到新版本。我以为我的代码是正确的，但它不太有效。 /var/www/html/gvsms 中有一个名为 .version 的文件，其中仅包含程序的版本。我想将该数字与安装程序的数字进行比较。但我不确定如何在 if 语句中执行。一个If中可以有多个If吗？这就是我到目前为止所得到的：

$installerver=1.1
$installedver=${cat /var/www/html/gvsms/.version}
echo "Installation beginning...."
echo " "
echo " "
echo -n "Checking to see if GVoice SMS Notification System was previously installed..."
if [ -a /var/www/html/gvsms/index.php ]; then 
   echo "Yes."
   echo ""
   echo "I have detected a previous installation of GVoice SMS Notification System."
   if [ $installerver == $installedver ]; then
       echo "The GVoice SMS Notification System is currently installed and is the same version as this installer. If you were trying to upgrade, please check the installer you downloaded and try again."
       exit
   fi
   elif [ $installedver == "0.5" || $installedver == "1.0"]; then
   while [[ "$yn" != "Yes" && "$yn" != "Y" && "$yn" != "y" && "$yn" != "yes" ]]; do
      echo "Would you like to upgrade? Yes or no."
      read -r  upgrade
      echo "$upgrade upgrade?"
      echo "Is this correct? (Yes or No)"
      read yn
   done
   echo "Upgrade proceeding..."
   fi
echo "No."
echo "I have not detected a previous installation of GVoice SMS Notification System."
read -p "To proceed with installation at your own risk, press Enter. Otherwise Ctrl-C."

现在程序错误如下：

./test.x: line 1: =1.1: command not found
./test.x: line 2: ${cat /var/www/html/gvsms/.version}: bad substitution

程序应该工作的方式是，如果检测到文件，则安装的版本与安装程序不同（或小于），并且用户说是要升级，应运行升级命令。如果用户拒绝升级，则退出脚本。

如果程序已安装并且与安装程序的版本相同，则显示错误消息并退出。

如果该程序尚未安装，请跳过重新确认安装并继续正常安装。

这可能吗？ 谢谢！

Answer 1

1. 将 shebang 行添加到脚本顶部：

   <前><代码>#!/bin/bash

2. 变量赋值无需美元符号即可完成：

   installerver=1.1
   

3. 子 shell 命令中的变量赋值使用括号而不是大括号：

   installedver=$(cat /var/www/html/gvsms/.version)
   

4. if 块中存在错误的 fi

5. 你缺少一个 else 块
6. 你可能应该在 cat'ing 之前测试该文件是否存在。
7. 您应该双引号所有变量
8. 您需要条件括号内有空格 [ … ] 和 [[ … ]]

这将使您的代码运行：

#!/bin/bash

installerver="1.1"
echo "Installation beginning...."
echo " "
echo " "
echo -n "Checking to see if GVoice SMS Notification System was previously installed..."
if [ -e "/var/www/html/gvsms/index.php" -a -r "/var/www/html/gvsms/.version" ]; then
   echo "Yes."
   echo ""
   echo "I have detected a previous installation of GVoice SMS Notification System."
   if [ "$(cat /var/www/html/gvsms/.version)" == "$installedver" ]; then
       echo "The GVoice SMS Notification System is currently installed and is the same version as this installer. If you were trying to upgrade, please check the installer you downloaded and try again."
       exit
   elif [ "$installedver" == "0.5" || "$installedver" == "1.0" ]; then
       while [[ "$yn" != "Yes" && "$yn" != "Y" && "$yn" != "y" && "$yn" != "yes" ]]; do
          echo "Would you like to upgrade? Yes or no."
          read -r  upgrade
          echo "$upgrade upgrade?"
          echo "Is this correct? (Yes or No)"
          read yn
       done
       echo "Upgrade proceeding..."
   fi
else
    echo "No."
    echo "I have not detected a previous installation of GVoice SMS Notification System."
    read -p "To proceed with installation at your own risk, press Enter. Otherwise Ctrl-C."
fi

Answer 2

您的作业有语法错误。分配给变量时，不要输入美元符号 $。对于命令替换，请使用括号 $(...)。

installerver=1.1
installedver=$(cat /var/www/html/gvsms/.version)

大括号用于简单的变量替换，如 echo "You buy $qty ${item}s."。