Re: dd: add 'skip_bytes' and 'count_bytes' operands

[Bernhard Voelker]

On 02/13/2012 04:06 PM, Bernhard Voelker wrote:
> Now, I see it: it's reading from *stdout*, not from stdin:
> 
> lseek(1, 0, SEEK_END)                   = -1 ESPIPE (Illegal seek)
> read(1, 0x616000, 512)                  = ?
> 
> It could issue an error if "seek=..." is used when fdesc is a tty.

Interestingly, read returns with EBADF if stdout is
redirected to /dev/tty:

  /usr/bin/printf "abc" | strace  src/dd seek=1 > /dev/tty
  ...
  lseek(1, 0, SEEK_END)                   = -1 ESPIPE (Illegal seek)
  read(1, 0x616000, 512)                  = -1 EBADF (Bad file descriptor)

but it blocks again when of=/dev/tty is given:

  /usr/bin/printf "abc" | strace src/dd seek=1 of=/dev/tty

I'm getting the impression that this is a kernel problem.

Have a nice day,
Berny