Path: utzoo!attcan!uunet!cs.utexas.edu!natinst!rpp386!jfh From: jfh@rpp386.cactus.org (John F. Haugh II) Newsgroups: comp.unix.wizards Subject: Re: UNIX history made easy Summary: History of the ``tacky bit'' explained. [ I can't believe you never heard of the tacky bit, Jim. ] Message-ID: <17090@rpp386.cactus.org> Date: 2 Oct 89 04:52:36 GMT References:<20226@usc.edu> <17085@rpp386.cactus.org> <1858@texsun.Central.Sun.COM> Reply-To: jfh@rpp386.cactus.org (John F. Haugh II) Organization: TrishTrash Readers, Inc. Lines: 39 In article <1858@texsun.Central.Sun.COM> jthomp@wintermute.Central.Sun.COM (Jim Thompson Sun Dallas IR) writes: >'sticky bit', John, 'sticky'. And back then it was on files, >not directories. (Well, ok, you could probably set it on >a directory (damn, where did I put that V6 listing?) but it >had no meaning. If you set it on an executable file, that file's >swap image would stay on the swap area after the program exited. >It was a wonderful hack to reduce overhead of often used programs. > >In recent BSD editions, the sticky bit has be overloaded for >directories to (not) permit 'unlink' operations in directories >otherwise writtable by the process in question. I can't believe I have to explain tacky bits to Jim. Jim Thompson, for those of you who -have- had your heads under rocks all your lives is the inventor of the Set-GID bit. Dennis Ritchie was giving a lecture on his recently patented Set-UID bit [ which was one of the first software patents -ever- ] and Jim very sarcastically said `Why don't you do it for groups too', and the idea was born. The purpose of the ``tacky bit'' was to get around the incredibly small disk partitions which were prevalent in the early 1970s. Any PC user is painfully aware of how small PC disks were [ typically around 10MB ]. Well, PDP-11 disks ran as small as 5MB each, often requiring 10 or 20 disk drives just to make a reasonably large /usr partition. What the tacky bit did was cause /unix to scan each subdirectory of a directory on file name lookups. So it would be possible to have ten or twenty subdirectories each with a different mounted file system all look like a single system image. The introduction of the RK07 disk drive did away with the need for the tacky bit, and it faded into obscurity with a few other worthless ideas, like `Save Stack on Swap', which saved a process's stack on the swapper after it exited. -- John F. Haugh II +-Things you didn't want to know:------ VoiceNet: (512) 832-8832 Data: -8835 | The real meaning of MACH is ... InterNet: jfh@rpp386.cactus.org | ... Messages Are Crufty Hacks. UUCPNet: {texbell|bigtex}!rpp386!jfh +--------------------------------------