Re: How to detect EADDRINUSE from an OSError exception

[adnan]

I actually want to catch a specific OSError, an OSError with errorCode 
EADDRINUSE. I want to port this to Nim: 
[https://gitlab.com/snippets/1903637](https://gitlab.com/snippets/1903637)

Note how I caught the specific exception, otherwise I raise exception again:
    
    
            
            auto sock = new Socket(AddressFamily.UNIX, SocketType.DGRAM);
            auto addr = new UnixAddress("\0com.gitlab.events.app.sock");
            const bool isPrimary = () {
                    try {
                            sock.bind(addr);
                    }
                    catch (SocketOSException e) {
                            import core.stdc.errno : EADDRINUSE;
                            
                            if (e.errorCode == EADDRINUSE) {
                                    log("Duplicate instance detected.");
                                    return false;
                            }
                            else {
                                    throw e;
                            }
                    }
                    log("Primary instance detected.");
                    return true;
            }();
    
    
    Run
    
    
        let sock: RawFd = socket(
            AddressFamily::Unix,
            SockType::Datagram,
            SockFlag::empty(),
            None, // Protocol
        )?;
        
        let addr = 
SockAddr::Unix(UnixAddr::new_abstract(SOCK_ADDR.as_bytes())?);
        
        match bind(sock, &addr) {
            Err(e) => match e {
                Sys(EADDRINUSE) => {
                    println!("Secondary instance detected, launching client.");
                    if client(sock, &addr).is_ok() {
                        println!("Message sent.");
                    }
                }
                _ => {
                    panic!("Socket binding failed due to: {:?}", e);
                }
            },
            Ok(_) => {
                println!("Primary instance detected, launching server.");
                server(sock)?;
            }
        }
    
    
    Run