The 4.2 UCBMail source has two files "sigretro.c" and "sigretro.h" that seem to do the trick. -- In-Real-Life: Chris Torek, Univ of MD Comp Sci UUCP: {seismo,allegra,brl-bmd}!umcp-cs!chris CSNet: chris at umcp-cs ARPA: chris.umcp-cs at CSNet-Relay