dear lazy web ... (UNIX pipes)

Ash Berlin ash_cpan at
Sat Apr 19 15:47:28 BST 2008

On 19 Apr 2008, at 15:40, Greg McCarroll wrote:

> So, I thought I knew how pipes worked from a distant OS class at uni.
> let say ...
>    process_that_generates_output | grep something
> now i thought that grep would be started around the same time as the
> first process and would grind through output when it had enough input
> to work on, and from this dim distant OS class I remember we
> implemented a special shared memory area in our own OS to do just
> that (this was 14 years ago).
> now today i wondered about,
>    process_that_generates_output | grep something | head

process_that_generates_output > dev/null

Will still run.

Think of the case where you only want the head of the output, but want  
the process to continue - nothing else is really sensible for general  

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