3.5.6 Process Substitution
Process substitution is supported on systems that support named
pipes (FIFOs) or the '/dev/fd' method of naming open files.
It takes the form of
<(list)
or
>(list)
The process list is run with its input or output connected to a
FIFO or some file in '/dev/fd'. The name of this file is
passed as an argument to the current command as the result of the
expansion. If the >(list) form is used, writing to
the file will provide input for list. If the
<(list) form is used, the file passed as an
argument should be read to obtain the output of list.
Note that no space may appear between the < or >
and the left parenthesis, otherwise the construct would be interpreted
as a redirection.
When available, process substitution is performed simultaneously with
parameter and variable expansion, command substitution, and arithmetic
expansion.
