On 10/27/2010 03:30 PM, Eric Blake wrote: >> I just tested on OpenBSD 4.7, FreeBSD 8.1, and MirBSD 10; that reports >> failure for all three of those distros. However, it also reports >> failure for dash 0.5.5.1 and latest dash.git, as well as pdksh. So the >> bug is pretty much inherited by all ash derivatives. >> >> It passes on bash, zsh, Solaris /bin/sh, and ksh93. > > Actually, bash 4.1 behaves oddly: > > $ bash -c 'ulimit -n 11; : <&-'; echo $? > 0 > $ bash -c 'ulimit -n 10; : <&-'; echo $? > bash: redirection error: cannot duplicate fd: Invalid argument > 0
In fact, bash is *silently* losing stdin for all subsequent commands. Compare: $ ksh -c 'ulimit -n 8; : <&-; exec 3<&0'; echo $? 0 $ bash -c 'ulimit -n 8; : <&-; exec 3<&0'; echo $? bash: redirection error: cannot duplicate fd: Invalid argument bash: 0: Bad file descriptor 1 I know exactly WHY bash and other shells are trying to dup() to 10 or greater - they MUST preserve the shell's std fds for commands after the temporary redirection done by ': <&-'. ksh93 is calling fcntl(fd,F_DUPFD,3) while bash and BSD sh are using fcntl(fd,F_DUPFD,10). At this point, I think that tar should fix its testsuite to use a larger ulimit -n setting; 10 is just too small for most shells out there, whether or not you also consider this a shell bug. -- Eric Blake ebl...@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org
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