Jan Vroonhof <vroonhof(a)math.ethz.ch&gt; writes: The I_[SG]ETSIG ioctl's are defined in bits/stropts.h which is part of glibc. The appended source seems to be the most minimal program showing differences. At a SUN result is '0' everytime, but here (glibc2.1) '-1', indicating the E_INVAL error. Perhaps the glibc is faulty; I will contact the developers next week. Nevertheless the method in sysdep.c (using I_GETSIG before I_SETSIG) seems to be wrong. The SUN streamio(7I) manpage says I_GETSIG can be called only if the process is already registered to receive the SIGPOLL signal. But to do this, I_SETSIG must be used. That's why calling I_GETSIG before I_SETSIG will fail. Enrico -- eMail: enrico.scholz(a)wirtschaft.tu-chemnitz.de talk: ensc(a)ultra.csn.tu-chemnitz.de