Editing Pipeline (Unix) (section)

==Creating pipelines programmatically==
Pipelines can be created under program control. The Unix <code>pipe()</code> [[system call]] asks the operating system to construct a new [[anonymous pipe]] object. This results in two new, opened file descriptors in the process: the read-only end of the pipe, and the write-only end. The pipe ends appear to be normal, anonymous [[file descriptor]]s, except that they have no ability to seek.

To avoid [[Deadlock (computer science)|deadlock]] and exploit parallelism, the Unix process with one or more new pipes will then, generally, call <code>[[fork (system call)|fork()]]</code> to create new processes. Each process will then close the end(s) of the pipe that it will not be using before producing or consuming any data. Alternatively, a process might create new [[pthreads|threads]] and use the pipe to communicate between them.

''[[Named pipe]]s'' may also be created using <code>mkfifo()</code> or <code>[[mknod]]()</code> and then presented as the input or output file to programs as they are invoked. They allow multi-path pipes to be created, and are especially effective when combined with standard error redirection, or with <code>[[tee (command)|tee]]</code>.