[allienaded]

I've made this basic plugin for my own server that just logs connections/disconnections (name, steamid, IP) and map changes in one file named Connections.log. This does not have the double logging bug.

What the log entries look like:

L 08/16/2014 - 14:53:18: -------- Mapchange to de_nuke --------
L 08/16/2014 - 14:53:18: Player 1<4><STEAM_1:0:********><><85.***.**.***> connected.
L 08/16/2014 - 15:01:33: Player 2<14><STEAM_1:0:********><><5.***.***.**> connected.
L 08/16/2014 - 15:01:59: Player 2<14><STEAM_1:0:********><><5.***.***.**> disconnected.
L 08/16/2014 - 15:15:53: Player 1<4><STEAM_1:0:********><><85.***.**.***> disconnected.

Source:

Spoiler

#include <sourcemod>

public Plugin:myinfo = 
{
    name = "Connection Logger",
    author = "STAV3",
    description = "Logs client Name, SteamID and IP.",
    version = "1.1",
    url = ""
}

public OnMapStart()
{
    new String:map[64];
    GetCurrentMap(map, sizeof(map));
    
    decl String:filepath[PLATFORM_MAX_PATH];
    BuildPath(Path_SM, filepath, sizeof(filepath), "logs/Connections.log");
    LogToFileEx(filepath, "-------- Mapchange to %s --------", map);
    return;
}

public OnClientAuthorized(client, const String:steamid[])
{
    if (IsFakeClient(client))
        return;
    
    new String:ip[64];
    GetClientIP(client, ip, sizeof(ip));
    
    decl String:filepath[PLATFORM_MAX_PATH];
    BuildPath(Path_SM, filepath, sizeof(filepath), "logs/Connections.log");
    LogToFileEx(filepath, "%L<%s> connected.", client, ip);
    return;
}

public OnClientDisconnect(client)
{
    if (IsFakeClient(client))
        return;
    
    new String:ip[64];
    GetClientIP(client, ip, sizeof(ip));
    
    decl String:filepath[PLATFORM_MAX_PATH];
    BuildPath(Path_SM, filepath, sizeof(filepath), "logs/Connections.log");
    LogToFileEx(filepath, "%L<%s> disconnected.", client, ip);
    return;
}

Source (old version):

Spoiler

#include <sourcemod>

public Plugin:myinfo = 
{
    name = "Connection Logger",
    author = "allienaded",
    description = "Logs client Name, SteamID and IP.",
    version = "1.0",
    url = ""
}

public OnMapStart()
{
    decl String:map[64];
    GetCurrentMap(map, sizeof(map));
    
    decl String:path[PLATFORM_MAX_PATH];
    BuildPath(Path_SM, path, sizeof(path), "logs/Connections.log");
    new Handle:file = OpenFile(path, "a");
    LogToOpenFileEx(file, "-------- Mapchange to %s --------", map);
    CloseHandle(file);
    return;
}

public OnClientAuthorized(client, const String:steamid[])
{
    if (IsFakeClient(client))
        return;
    
    new String:ip[64];
    GetClientIP(client, ip, sizeof(ip));
    
    decl String:path[PLATFORM_MAX_PATH];
    BuildPath(Path_SM, path, sizeof(path), "logs/Connections.log");
    new Handle:file = OpenFile(path, "a");
    LogToOpenFileEx(file, "%L<%s> connected.", client, ip);
    CloseHandle(file);
    return;
}

public OnClientDisconnect(client)
{
    if (IsFakeClient(client))
        return;
    
    new String:ip[64];
    GetClientIP(client, ip, sizeof(ip));
    
    decl String:path[PLATFORM_MAX_PATH];
    BuildPath(Path_SM, path, sizeof(path), "logs/Connections.log");
    new Handle:file = OpenFile(path, "a");
    LogToOpenFileEx(file, "%L<%s> disconnected.", client, ip);
    CloseHandle(file);
    return;
}