Eric Blake writes: > > Indeed, reading the original V7 source code from 1979: > http://minnie.tuhs.org/cgi-bin/utree.pl?file=3DV7/usr/src/cmd/rm.c > [...] > > shows that _only_ ".." was special, "." was attempted in-place and > didn't fail until the unlink(".") after the directory itself had been > emptied. It wasn't until later versions of code that "." also became > special.
I also decided to look around there, and found some of the turning points: Up to 4.2BSD, the V7 behavior was kept. (http://minnie.tuhs.org/cgi-bin/utree.pl?file=4.2BSD/usr/src/bin/rm.c) rm -rf . was forbidden in 4.3BSD (26 years ago). http://minnie.tuhs.org/cgi-bin/utree.pl?file=4.3BSD/usr/src/bin/rm.c The removal of dir/. (and dir/..) was not forbidden until Reno. http://minnie.tuhs.org/cgi-bin/utree.pl?file=4.3BSD-Reno/src/bin/rm/rm.c cp = rindex(arg, '/'); if (cp == NULL) cp = arg; else ++cp; if (isdot(cp)) { fprintf(stderr, "rm: cannot remove `.' or `..'\n"); return (0); } Maybe the classical behavior stuck around longer in the more SysV-ish Unices. The Ultrix-11 3.1 tree on TUHS from 1988 has a rm that looks very much like V7, but I can't find anything to compare it to until OpenSolaris. Did POSIX force BSD to change their rm in 1988? I think it's more likely that POSIX simply documents a restriction that BSD had already added. Either way the latest POSIX revisions certainly can't be blamed. -- Alan Curry
