- fcntl/dupfdconstant
- fcntl/getfdconstant
- fcntl/setfdconstant
- fcntl/getflconstant
- fcntl/setflconstant
Operations used with file-control.
NOTE: On native Windows builds (all except cygwin), these are all defined as zero. The file-control procedure to use these with is also unimplemented and will raise an error when called.