Mkfifo
mkfifo create a named pipe. Opening a FIFO for reading normally blocks until some other process opens the same FIFO for writing, and vice versa.
You need two shell.
Create the fifo
mkfifo /tmp/fifo1
Try to read from the fifo will block until we write inside
cat /tmp/fifo1
In the second shell write something in the fifo
echo "Hello fifo" > /tmp/fifo1
The cat from the first shell should have write Hello fifo