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| os.execute ([command])
| 
| This function is equivalent to the C function system. It passes
| command to be executed by an operating system shell. It returns
| a status code, which is system-dependent. If command is absent,
| then it returns nonzero if a shell is available and zero otherwise.

An empty string does not crash. But it does not help, because
I want to use the variant without argument.

Yours sincerely
  Heiko Oberdiek