PAC (Proxy Auto-Config)

Something has been bothering me for a long time:

• I'm a heavy macOS user. Thanks to excellent macOS software like Surge for Mac, I can solve almost any network problem with ease.

• But on Windows and Linux, things get considerably more complicated—and using Windows or Linux is still necessary.

• I don't want to install a separate piece of software on every system and write a config file for each one.

Therefore, the best approach is to use Surge for Mac as a proxy server to take over networking for other devices.

I'm on a large campus intranet and can't assign a static IP to my Mac, so I have to keep updating the Mac's IP address to keep this setup working.

With ChatGPT's help, I wrote a script that automatically fetches the Mac's IP address, generates a PAC (Proxy Auto-Config) configuration file, and uploads it to my cloud drive. Other devices just need to enter the URL of the configuration file.

1. Save the following code as generate_pac.sh. The script generates a proxy.pac file in the same directory and uploads it to the cloud drive using Alist's WebDAV feature.

   Shell

   #!/bin/zsh
   
   cd /Users/jayden/proxy_pac
   # 保证环境变量的一致以成功获取到 ip 地址。
   PATH=/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
   
   rm -f proxy.pac
   
   # Get the local IP address from interface en0 (commonly used for Wi-Fi)
   LOCAL_IP=$(ipconfig getifaddr en0)
   
   # Proxy ports
   HTTP_PROXY_PORT=6152
   SOCKS_PROXY_PORT=6153
   
   # PAC file path
   PAC_FILE="proxy.pac"
   
   # Generate the PAC file
   cat <<EOL > $PAC_FILE
   function FindProxyForURL(url, host) {
       var http_proxy = "PROXY $LOCAL_IP:$HTTP_PROXY_PORT";
       var socks_proxy = "SOCKS5 $LOCAL_IP:$SOCKS_PROXY_PORT";
   
       // Add your proxy rules here
       if (shExpMatch(host, "*.example.com")) {
           return "DIRECT"; // Direct connection
       }
   
       // Default to using HTTP proxy
       return http_proxy + "; " + socks_proxy;
   }
   EOL
   
   echo "PAC file generated at $PAC_FILE" >> proxy_pac.log
   
   # Upload the PAC file to Alist via WebDAV
   curl -X DELETE https://pan.xxu.do/dav/path/to/proxy.pac -u username:password
   curl -T $PAC_FILE https://pan.xxu.do/dav/path/to/proxy.pac -u username:password
   
   echo "PAC file generated and uploaded to Alist" >> proxy_pac.log
   
   date >> proxy_pac.log
   

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2. Set up a scheduled task:

   ShellCopy

   crontab -e
   

   Then add this line to the end (it runs every hour at the half-hour mark; feel free to adjust it to your needs):

   CRONCopy

   30 * * * * /Users/jayden/proxy_pac/generate_pac.sh