Nicolas Williams wrote: > On Fri, Dec 12, 2008 at 05:36:36PM -0600, Nicolas Williams wrote: > > So, yes, open(2) of /dev/fd/N is as a dup(2) of N. > > Also, every reference I can find says that open(2) of /dev/fd/N is > supposed to be a dup(2) of file descriptor N, on Solaris, on Linux, on > BSD, on Plan 9. > > And, apparently also the convention is that open(2) of /proc/self/fd/N > is NOT equivalent to dup(2) of fd N (it opens the same file, device, > whatever, but does not keep the offset from fildes N). > > % (read line <#((200)) ; print $line ; read line > </proc/self/fd/9 ; print $line) <&9 > 1041 > 1001 > % > > And that's supposed to be so for Linux and Solaris (haven't checked > BSD). An open(2) of /proc/self/fd/N is supposed to check file > permissions too: > > % pfexec chown root /tmp/foo > % pfexec chmod 600 /tmp/foo > % (read line <#((200)) ; print $line ; read line > </proc/self/fd/9 ; print $line) <&9 > 1041 > ksh93: /proc/self/fd/9: cannot open [Permission denied] > 1041 > %
Without looking at the matching code... does the standard (assuming |openat()| passed the standards yet) about |cloned_fd = openat(original_fd, ".", ...)| (the idea is to reference the current fd as "." and hope it will open another fd to the same file) ? ---- Bye, Roland -- __ . . __ (o.\ \/ /.o) roland.mainz at nrubsig.org \__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer /O /==\ O\ TEL +49 641 3992797 (;O/ \/ \O;)
