how big is a pipe?

[jbn at wdl1.UUCP]

     Approaches differ.  In AT&T's UNIX, a pipe is implemented as a circular
buffer in a file, normally four blocks long.  But if the pipe is reasonably
active the buffers never get written to the disk; all the action is in
the buffer cache.  In 4.2BSD, a pipe is a special case of a socket, and the
operation is performed entirely in memory.  In MS-DOS, a pipe is an illusion
created by the command interpreter; "p1 | p2" is implemented as 
"p1 > tmp; p2 < tmp; rm tmp".  

						John Nagle