Scheme 48 Manual | Contents | In Chapter: Command processor
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## Switches

There are a number of binary switches that control the behavior of the command processor.

The switches are as follows:

  `batch [on | off]`
  In `batch mode' any error or interrupt that comes up will cause Scheme 48 to exit immediately with a non-zero exit status. Also, the command processor doesn't print prompts. Batch mode is off by default.

  `,levels [on | off]`
  Enables or disables the automatic pushing of a new command level when an error, interrupt, or other breakpoint occurs. When enabled (the default), breakpoints push a new command level, and <eof> (see above) or `,reset` is required to return to top level. The effects of pushed command levels include:
  - a longer prompt
  - retention of the continuation in effect at the point of errors
  - confusion among some newcomers
  With `levels` disabled one must issue a `,push` command immediately following an error in order to retain the error continuation for debugging purposes; otherwise the continuation is lost as soon as the focus object changes. If you don't know anything about the available debugging tools, then levels might as well be disabled.

  `break-on-warnings [on | off]`
  Enter a new command level when a warning is produced, just as when an error occurs. Normally warnings only result in a displayed message and the program does not stop executing.

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