Re: Problem with line buffered IO when no tty

[Steven W. Orr]

On 7/7/2011 9:21 AM, Eric Blake wrote:
> On 07/07/2011 06:55 AM, Steven W. Orr wrote:
> > So, why is it that bash is behaving like it is always line buffered or
> > unbuffered, even if there is no console?
>
> Because POSIX requires 'sh' to behave like it is unbuffered:
>
> http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sh.html
>
> When the shell is using standard input and it invokes a command that
> also uses standard input, the shell shall ensure that the standard input
> file pointer points directly after the command it has read when the
> command begins execution. It shall not read ahead in such a manner that
> any characters intended to be read by the invoked command are consumed
> by the shell (whether interpreted by the shell or not) or that
> characters that are not read by the invoked command are not seen by the
> shell.
>
> Bash meets this requirement by reading one byte at a time on
> non-seekable input, rather than relying on the decision of libc on
> whether stdin defaults to fully-buffered or line-buffered.

Thank you! That's what I was looking for. :-)

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