Redirection of coprocess input and output

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The standard input and output of a coprocess is reassigned to a numbered file descriptor by using I/O redirection.

For example, the command: 
exec 5>&p
moves the input of the coprocess to file descriptor 5.
After this coprocess has completed, you can use standard redirection syntax to redirect command output to the coprocess. You can also start another coprocess. Output from both coprocesses is connected to the same pipe and is read with the read -p command. To stop the coprocess, type the following: 
read -u5