Using the tee command to do two different operations

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http://unix.stackexchange.com – I am trying to take the input from a serial port and write it to a file and also then read the file and send it back out the serial port to the host computer. A coworker suggested using the "tee" command but I can't find a good example/wrap my mind around the command. Is it possible to do this with "tee"? it seems that tee can only do one command, like cating a file to a different place, but not cating the port then writing to the document then reading the document and then sending it over the port. Or am i just not understanding the basics of the "tee" command. -Thanks (HowTos)