Quoting <asm/ioctls.h>: > #if defined(__USE_MISC) || defined (__KERNEL__) > #define tIOC ('t' << 8) > #endif Could somebody try to explain this to me? I'm especially interested in the #if part. Why isn't tIOC defined normally? It is used later. in the file - and it is used externally by rp-pppoe for example. Regards, Joey -- All language designers are arrogant. Goes with the territory... -- Larry Wall