Pipeline synchronization - sh vs ksh

[Gordon Stewart]

Typically, there is one FIFO (a special kind of file that implements
pipes) open for each symbol "|" in a line of shell script.  The flow
is designed in such a way that reading processes have input
and writing processes can write, and nobody will
read on an empty pipe. This means that there will typically be stuff in
all the pipes in a 'sh' command, with the processes runnning
concurrently.
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