Re: [TUHS] moving directories in svr2

Just get the 4.1 man pages and it says: "Directories may only be moved within the same parent directory." On Wed, Dec 29, 2021 at 10:44 AM Will Senn <will.senn(a)gmail.com> wrote: > On 12/29/21 9:17 AM, Clem Cole wrote: > > Not until the BSD rename system call,. > > Try it on V6 or V7 and you will get 'directory exists' as an error. > > Sure enough. I never really noticed. I guess cuz I was careful about > creating directories in the first place. > > Think about the UNIX FS and the link system call. How is mv implemented? > You link the file to the new directory and the unlink it from the old > one. But a directory file can not be in two directories at the same time > as the .. link would fail. When Joy created the rename system call it > became possible. Until System V picked it up (IIRC was SVR3), only system > that supported the BSD world. > > Nice summary. I will add it to my systems programming investigations > list. > > What I have forgotten is if the BSD mv command for 4.1 supported it. If > it did then it was not atomic -- it would have had to create the new > directory, move the contents independently and then remove the old one. > > FWIW: when we did the first SMP UNIX at Masscomp we had supported the BSD > FS and the 4.1c/4.2 system calls. Joy's implementation of rename was a > real mess. Making it atomic, supporting an SMP and deal with all the > recovery paths on an error took some work. It's funny, the rename system > call is a simple idea, but on a failure when partially thru it, makes > unwinding the partial completion an interesting problem. > > It's impressive what early work was done and how few today really > understand the challenges that were met and overcome to give us our cushy > oses. > > > Clem > > On Wed, Dec 29, 2021 at 9:34 AM Will Senn <will.senn(a)gmail.com> wrote: > >> I'm a little flummoxed in trying to move some directories around in >> svr2. Shouldn't the following work? >> >> mkdir a >> mkdir b >> mv a b >> >> I get the following error: >> mv: b exists >> >> I tried many of the possible variants including: >> >> mv a b/ >> mv: b/ exists >> mv a b/a >> mv: directory rename only >> cd b >> mv ../a . >> mv: . exists >> mv ../a ./ >> mv: ./ exists >> mv ../a ./a >> mv: directory rename only >> >> >> If moving directories into existing directories wasn't allowed in those >> days, 1) how were directories managed? and 2) when did moving directories >> into directories become a thing? >> >> >> >