package require Wait
set fds [Pipe] set readpipe [lindex $fds 0] set writepipe [lindex $fds 1]
Produces a unix pipe and binds both the readable and writeable sides of the pipe to Tcl channels. One use case for this is to setup a communications channel between Tcl threads (see thread::trasnfer in the Tcl thread package).
Other use cases include ssetting up pipes to capture output, or error of intermediate stages of Tcl pipelines created with exec or open.
This command never failas. It produces a two element list.
The first element of the list is the read side of the pipe and
the second the write side. This matches the implementation of
the Unix pipe(2) system service.