Other interesting strings were similarly found within libsteam_api_linux.so such as "[S_API FAIL] SteamAPI_Init() failed; unable to update local steamclient. Continuing with current version anyway." These strings for the Linux shared libraries were the similar to the Microsoft DLL files used by the Steam client on Windows. There were also strings referencing a Steam 3 release client on a Linux file-system (/home/VALVE/alfred/valve/steam3_rel_client/) likely belonging to Alfred Reynolds, who has long been involved with Valve's Linux operations. However, the Linux Steam client library doesn't appear to be an exact replica of the steamclient.dll, which has about twice the number of strings currently.
Also in the latest version of the Steam.exe is a "Bad eCurrentLinuxClientVersion field in CClientConfigRecord" string, taking note of the Linux client version.
Could Left 4 Dead be Valve's first game with a native Linux client? Judging by the popularity of this brand new title, it certainly wouldn't be a bad launch title. Alternatively, perhaps Valve messed up in prematurely pushing out these Linux files with the demo? These shared libraries compiled for Linux add over 50MB to the download size (with steamclient_linux.so being 30MB alone), so they should have a good reason as to why they are shipping them on Windows. For those that use both Windows and Linux, it looks like it will be a single Steam game download will be compatible with both operating systems. This is similar to how the Linux clients for titles from id Software and Epic Games operate with a vast majority of the in-game content files being cross-platform and then just having a few Linux-specific files that need to be dropped in for the operating system support.
Further reiterating a point from our previous article, Postal III is being released in 2009 by Running With Scissors. Vince Desi, the CEO of Running With Scissors, has officially confirmed that Postal III will be available for Linux and it too uses Valve's Source Engine.
So what we have with Left 4 Dead are several Linux shared libraries shipping with the demo on Windows. It's odd that they would ship the .so libraries in addition to the Microsoft DLL files without an official Linux client or even a Linux server binary in the same download, but they did, and this is the first Steam game we have encountered where these Linux files can be found. We are not even talking about the server-only version. It's looking good though that Linux support for the Steam client and Source Engine, which should come hand-in-hand, will be here in the not too distant future.