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Stream Variables

Variables whose values must be streams are sometimes called stream variables .

Certain stream variables are defined by this specification to be the proper source of input or output in various situations where no specific stream has been specified instead. A complete list of such standardized stream variables appears in Figure 21-6. The consequences are undefined if at any time the value of any of these variables is not an open stream.

  Glossary Term    Variable Name      
  debug I/O        *debug-io*         
  error output     *error-output*     
  query I/O        *query-io*         
  standard input   *standard-input*   
  standard output  *standard-output*  
  terminal I/O     *terminal-io*      
  trace output     *trace-output*     


  Figure 21--6: Standardized Stream Variables

Note that, by convention, standardized stream variables have names ending in "-input*" if they must be input streams, ending in "-output*" if they must be output streams, or ending in "-io*" if they must be bidirectional streams.

User programs may assign or bind any standardized stream variable except *terminal-io*.