Name

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  FXGFILTERED

Author

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  Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
  craigm@lheamail.gsfc.nasa.gov
  UPDATED VERSIONs can be found on my WEB PAGE:
      http://cow.physics.wisc.edu/~craigm/idl/idl.html

Purpose

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  Determine if a unit has been opened by FXGOPEN.

Major Topics

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  File I/O, Pipes, URLs, FITS

Calling Sequence

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  Q = FXGFILTERED(UNIT)

Description

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  FXGFILTERED is a function which determines whether a UNIT has been
  opened by FXGOPEN and requires special handling.
  In principle, only 'FXG' procedures should be used to access file
  units returned by FXGOPEN. However, if the unit turns out to be a
  normal file then special treatment is not required. User programs
  can use the FXGFILTERED function to find out this information.
  If FXGFILTERED returns 0, then normal file-access procedures (such
  as READU, WRITEU, CLOSE, and POINT_LUN) can be used. Otherwise,
  the 'FXG' routines must be used.

Inputs

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  UNIT - Any file LUN.

Returns

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  0 - resource is a normal file.
  1 - resource is not a normal file.

Example

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  if fxgfiltered(unit) EQ 0 then begin
    ;; If zero then can use standard IDL routines
    point_lun, unit, position
    readu, unit, buffer
    close, unit
  endif

Modification History

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  Written, 1999, CM
  Documented, 02 Oct 1999, CM
  Changed copyright notice, 21 Sep 2000, CM

Todo

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  * Add more protocols
  * Make more windows friendly