Bash驗證和條件語句

Question

我正在爲bash中的程序編寫安裝腳本。安裝的第一部分檢測程序是否已安裝。這通過指定目錄中文件的存在來檢測。這部分工作正常。但是，如果舊版本存在，我希望用戶能夠升級到新版本。我認爲我的代碼是正確的，但它不起作用。/var/www/html/gvsms中有一個名爲.version的文件，它只是在文件中具有該程序的版本。我想將該數字與安裝程序的編號進行比較。不過，我不確定在if語句中如何。 If裏面可以有多個Ifs？這是我到目前爲止有：

$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." 

眼下與程序出現了錯誤：

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

程序應該工作的方式是，如果檢測到文件，安裝的版本是不（或小於）與安裝程序相同，並且用戶說是升級，則應運行升級命令。如果用戶說不要升級，請退出腳本。

如果程序已安裝並且與安裝程序版本相同，則顯示錯誤消息並退出。

如果程序尚未安裝，請跳過重新確認安裝並繼續正常安裝。

這可能嗎？ 謝謝！

Answer 1

您的作業有語法錯誤。分配給變量時，不要放置美元符號$。而對於命令替換，請使用括號$(...)。

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

大括號爲簡單變量替換，如在echo "You bought $qty ${item}s."。

Answer 2

1. 的家當行添加到腳本頂部：

   #!/bin/bash 
   

2. 變量賦值，而不使用美元符號進行：從一個子shell命令使用

   installerver=1.1 
   

3. 變量賦值括號中沒有大括號：

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

4. 有一個壞fi你如果塊

5. 你錯過了一個else塊
6. 你也許應該測試，如果文件cat'ing之前存在。
7. 你應該用雙引號所有的變量
8. 您需要有條件的括號[ … ]和[[ … ]]

內部空間這將讓你的代碼運行：

#!/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