Hi, I'm seeing some strange behavior with dd. The first two commands work and report the expected number of records transferred (1024):
dd if=/dev/zero bs=1MB count=1024 of=/dev/null dd bs=1MB count=1024 </dev/zero >/dev/null But these report a random number of records, usually somewhere around 200, but as few as 0 or as many as 1005: cat /dev/zero |dd bs=1MB count=1024 of=/dev/null cat /dev/null |dd bs=1MB count=1024 >/dev/null An strace on dd shows that the last read/write pair both succeed and then dd inexplicably closes both files. None of the reads return zero or failure. An strace on cat shows that its last write to stdout gets a sigpipe, so it really is trying to send the data to dd and it's dd that's closing the pipe. Replacing /dev/null with a real file exhibits the behavior one would expect. Substituting some other I/O-counting command for dd works fine. Any insights here? Thanks, Robb Version info: coreutils-6.10-r2 gcc-4.1.2 x86_64 linux-2.6.25 and 2.6.27 (also tested on Ubuntu-8.10 i686 with same results) -- Robb Matzke L-159 | Ph: 812-967-6325 | I/O, I/O, it's off to disk we go, Lawrence Livermore | Fax: 812-967-6326 | A petabyte to read or write, National Laboratory | Hrs: 3am-11am PDT | I/O, I/O.
