This command takes a list of names of files that have been previously opened via an OUT statement and closes them. Most systems require this action by the user before he ends the REDUCE job (if not sooner), otherwise the output may be lost. If a file is shut and a further OUT command issued for the same file, the file is erased before the new output is written.
If it is the current output file that is shut, output will switch to the terminal. Attempts to shut files that have not been opened by OUT, or an input file, will lead to errors.