今天看到一个脚本，翻到SPOOL命令，就查了一下.
先说说spool out 和 spool off 吧，书中的解释：
SPOOL：Represents the name of the file to which you wish to spool. SPOOL followed
byfile_name begins spooling displayed output to the named file. If you do not
specify an extension, SPOOL uses a default extension (LST or LIS on most systems).
OFF : Stops spooling.
OUT:
Stops spooling and sends the file to your host computer's standard (default) printer.
简而言之，摘录一下大神的总结 “OUT = OFF + PRINT”。
