[OT]-ish: Can someone explain this?

[Abigail]

On Sat, Jul 02, 2011 at 02:07:08PM -0700, Randy J. Ray wrote:
> On 07/02/2011 10:04 AM, Andrew Suffield wrote:
>> On Sat, Jul 02, 2011 at 05:32:38PM +0100, Dirk Koopman wrote:
>>> But how come I get output at a shell prompt, and not down a pipe (or
>>> a redirection either)? What special magic is occurring here?
>>
>> If:
>>
>> 1. isatty() is true on the underlying fd of the FILE*
>>
>> and:
>>
>> 2. The string contains \n
>>
>> then printf calls fflush().
>>
>> In your first instance, stdout was your terminal, and in the second it
>> was one end of a pipe.
>
> That was my first thought, but I wasn't 100% sure. Glad to see I was 
> right, and haven't *completely* forgotten my C minutiae...
>


Perl behaves in the same way. Output is by default buffered, but when
the output channel is interactive, output is flushed at each newline.


Abigail