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obssys: define the version of the observing system to use

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Function:

obssys defines which version of the observing system will be used. It does not start any part of the system.

Usage:

   obssys

Notes and caveats:

The obssys command is usually implemented as an alias to an obssys program. The alias typically passes some default arguments to the script so executing the program directly, without the default arguments, will usually not define the correct system.

obssys defines two crucial environment variables: PATH and OBSSYS. The former is the normal Unix search-path for programs, and obssys adds the appropriate observing-system directory at the start of the path. The latter defines the root directory of the observing system and is used by the system to locate configuration and log files.