PAC (Proxy Auto-Config)

I have been troubled by one thing for a long time:

I am a heavy macOS user and it is easy for me to solve almost all network problems on macOS, thanks to excellent software like Surge for Mac.
However, things are more complicated on Windows and Linux, but using Windows or Linux is still necessary.
I don't want to deploy software and write configuration files for each system.

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

I am in a large intranet at school and cannot set the IP of my Mac to static, so I need to constantly update the IP address of my Mac to maintain this solution.

With the help of ChatGPT, I wrote a script that automatically obtains the IP address of my Mac and generates a PAC (Proxy Auto-Config) configuration file, which is uploaded to my cloud storage. Other devices only need to fill in the address of the configuration file.

Save the following code as generate_pac.sh. This script will generate a proxy.pac file in the same directory and upload it to the cloud storage using the webdav feature of alist.

#!/bin/zsh

cd /Users/jayden/proxy_pac
# Ensure consistent environment variables to successfully obtain the IP address.
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

Set up a scheduled task:
```
crontab -e
```
Then add this line to the end (run every half hour, you can adjust it according to your needs):
```
30 * * * * /Users/jayden/proxy_pac/generate_pac.sh
```

This article is synchronized and updated to xLog by Mix Space.
The original link is https://xxu.do/posts/geek/PAC