zsh脚本检测macOS次要更新时字符串匹配异常求助

我正在编写一个脚本，用于检测哪些Mac设备存在可用的macOS次要软件更新。在变量中搜索连续两个单词时，我遇到了异常行为：尽管所有Mac都安装了相同版本的macOS（13.5.1或14.1），但脚本在部分设备上正常运行，在另一部分设备上却错误提示无可用更新。

原脚本如下：

#!/bin/zsh

deviceDarwinNum=$(sw_vers | grep BuildVersion | awk {'print $2'} | cut -c1-2)

if [[ 22 == $deviceDarwinNum ]]; then
  echo "macOS Ventura is installed"
  installedmacOSVersion="Ventura"
fi


checkupdate=$(softwareupdate -l 2>&1)

echo $checkupdate

if [[ $checkupdate == *"macOS $installedmacOSVersion"* ]]; then
  echo "==> macOS $installedmacOSVersion software update available <=="

else
  echo "==> NO macOS $installedmacOSVersion software update available <=="
  exit 1
fi

执行结果：

Script result: macOS Ventura is installed

Software Update Tool

Finding available software
Software Update found the following new or updated software:
* Label: Command Line Tools for Xcode-15.0
    Title: Command Line Tools for Xcode, Version: 15.0, Size: 721962KiB, Recommended: YES, 
* Label: Safari17.1VenturaAuto-17.1
    Title: Safari, Version: 17.1, Size: 162063KiB, Recommended: YES,
* Label: macOS Ventura 13.6.2-22G320
    Title: macOS Ventura 13.6.2, Version: 13.6.2, Size: 492979KiB, Recommended: YES, Action: restart,  
* Label: macOS Sonoma 14.1.1-23B81
    Title: macOS Sonoma 14.1.1, Version: 14.1.1, Size: 4460818KiB, Recommended: YES, Action: restart, 

==> NO macOS Ventura software update available <==

可以看到softwareupdate命令已检测到可用更新，但脚本却判断为无可用更新。我尝试将变量$installedmacOSVersion替换为固定值"Ventura"或"Sonoma"，问题仍然存在。之后我改用另一种if语句写法，问题依旧未解决：

#!/bin/zsh

deviceDarwinNum=$(sw_vers | grep BuildVersion | awk {'print $2'} | cut -c1-2)

if [[ 22 == $deviceDarwinNum ]]; then
  echo "macOS Ventura is installed"
  installedmacOSVersion="Ventura"
fi


checkupdate=$(softwareupdate -l 2>&1)

echo ""
echo $checkupdate
echo ""

if echo "$checkupdate" | grep -q "macOS $installedmacOSVersion"; then
  echo "==> macOS $installedmacOSVersion software update available <=="

else
  echo "==> NO macOS $installedmacOSVersion software update available <=="
  exit 1
fi

问题根源 #

1. 特殊空格字符导致匹配失败：脚本中用于匹配的字符串里，macOS和变量之间的空格不是普通半角空格，而是不间断空格（Non-breaking Space）或其他特殊空格字符。这类字符肉眼与普通空格无区别，但shell会将其视为不同字符，直接导致匹配失效。
2. 系统版本判断不完整：原脚本仅处理了Ventura（Darwin 22）的情况，未覆盖Sonoma（Darwin 23），会导致Sonoma设备的installedmacOSVersion变量为空，匹配必然失败。

修复步骤 #

1. 替换特殊空格为普通半角空格 #

检查并修改脚本中所有匹配字符串里的空格，确保macOS和变量之间是键盘空格键输入的普通半角空格。例如将*"macOS $installedmacOSVersion"*修改为*"macOS $installedmacOSVersion"*。

2. 完善系统版本判断逻辑 #

补充Sonoma的判断分支，避免变量为空：

if [[ 22 == $deviceDarwinNum ]]; then
  echo "macOS Ventura is installed"
  installedmacOSVersion="Ventura"
elif [[ 23 == $deviceDarwinNum ]]; then
  echo "macOS Sonoma is installed"
  installedmacOSVersion="Sonoma"
else
  echo "Unsupported macOS version"
  exit 1
fi

3. 优化匹配逻辑（可选） #

针对softwareupdate的输出格式，使用更精准的匹配规则，比如匹配更新标签中的系统版本：

if echo "$checkupdate" | grep -q "Label: macOS $installedmacOSVersion "; then
  echo "==> macOS $installedmacOSVersion software update available <=="
else
  echo "==> NO macOS $installedmacOSVersion software update available <=="
  exit 1
fi

修复后的完整脚本 #

#!/bin/zsh

# 获取Darwin主版本号，简化命令
deviceDarwinNum=$(sw_vers -buildVersion | cut -c1-2)

# 判断当前系统版本
if [[ 22 == $deviceDarwinNum ]]; then
  echo "macOS Ventura is installed"
  installedmacOSVersion="Ventura"
elif [[ 23 == $deviceDarwinNum ]]; then
  echo "macOS Sonoma is installed"
  installedmacOSVersion="Sonoma"
else
  echo "Unsupported macOS version"
  exit 1
fi

# 获取更新列表
checkupdate=$(softwareupdate -l 2>&1)

echo ""
echo "$checkupdate"
echo ""

# 检查是否有对应系统的更新
if echo "$checkupdate" | grep -q "macOS $installedmacOSVersion "; then
  echo "==> macOS $installedmacOSVersion software update available <=="
else
  echo "==> NO macOS $installedmacOSVersion software update available <=="
  exit 1
fi

内容的提问来源于stack exchange，提问作者Thrawnium